Publications

This is intended to be a reasonably complete list of my publications, though it may not always be completely up-to-date.

Other places to look are on my orcid profile and on NASA ADS.


SunPy: A Python package for Solar Physics

The Journal of Open Source Software, 5, 1832

Python C Astronomy Solar physics IDL

| doi:10.21105/joss.01832 |

    @article{ 2020JOSS....5.1832M,
    
    title = { SunPy: A Python package for Solar Physics },
    journal = { The Journal of Open Source Software },
    year = { 2020 },
    month = { February },
    volume = { 5 },
    number = { 46 },
    pages = { 1832 },
    doi = { 10.21105/joss.01832 },
    }
    

A Precessing Numerical Relativity Waveform Surrogate Model for Binary Black Holes: A Gaussian Process Regression Approach

Daniel Williams, Ik Siong Heng, Jonathan Gair, James Clark, Bhavesh Khamesra

Physical Review D, 101, 6

general relativity and quantum cosmology physics - data analysis statsistics and probability gravitational waves gravitational waves: modelling

| arxiv:1903.09204 | doi:10.1103/PhysRevD.101.063011 |

Gravitational wave astrophysics relies heavily on the use of matched filtering both to detect signals in noisy data from detectors, and to perform parameter estimation on those signals. Matched filtering relies upon prior knowledge of the signals expected to be produced by a range of astrophysical systems, such as binary black holes. These waveform signals can be computed using numerical relativity techniques, where the Einstein field equations are solved numerically, and the signal is extracted from the simulation. Numerical relativity simulations are, however, computationally expensive, leading to the need for a surrogate model which can predict waveform signals in regions of the physical parameter space which have not been probed directly by simulation. We present a method for producing such a surrogate using Gaussian process regression which is trained directly on waveforms generated by numerical relativity. This model returns not just a single interpolated value for the waveform at a new point, but a full posterior probability distribution on the predicted value. This model is therefore an ideal component in a Bayesian analysis framework, through which the uncertainty in the interpolation can be taken into account when performing parameter estimation of signals.
    @article{ 2019arXiv190309204W,
    author = { Williams, D } and { Heng, IS } and { Gair, J } and { Clark, JA } and { Khamesra, B },
    title = { A Precessing Numerical Relativity Waveform Surrogate Model for Binary Black Holes: A Gaussian Process Regression Approach },
    journal = { Physical Review D },
    year = { 2020 },
    volume = { 101 },
    doi = { 10.1103/PhysRevD.101.063011 },
    }
    

Comparing Short Gamma-Ray Burst Jet Structure Models

Fergus Hayes, Ik Siong Heng, John Veitch, Daniel Williams

Astrophysical Journal, 891, 124

gamma-ray burst: general gravitational waves

| arxiv:1911.04190 | doi:10.3847/1538-4357/ab72fc |

A structured gamma-ray burst jet could explain the dimness of the prompt emission observed from GRB170817A but the exact form of this structure is still ambiguous. However, with the promise of future joint gravitational wave and gamma-ray burst observations, we shall be able to examine populations of binary neutron star mergers rather than a case-by-case basis. We present an analysis that considers gravitational wave triggered binary neutron star events both with and without short gamma-ray burst counterparts assuming that events without a counterpart were observed off-axis. This allows for Bayes factors to be calculated to compare different jet structure models. We perform model comparison between a Gaussian and power-law apparent jet structure on simulated data to demonstrate that the correct model can be distinguished with a log Bayes factor of >5 after less than 100 events. Constraints on the apparent structure jet model parameters are also made. After 25(100) events the angular width of the core of a power-law jet structure can be constrained within a 90% credible interval of width ∼9.1(4.4)∘, and the outer beaming angle to be within ∼19.9(8.5)∘. Similarly we show the width of a Gaussian jet structure to be constrained to ∼2.8(1.6)∘.
    @article{ 2020ApJ...891..124H,
    author = { Hayes, F } and { Heng, IS } and { Veitch, J } and { Williams, D },
    title = { Comparing Short Gamma-Ray Burst Jet Structure Models },
    journal = { Astrophysical Journal },
    year = { 2020 },
    month = { mar },
    volume = { 891 },
    number = { 2 },
    pages = { 124 },
    doi = { 10.3847/1538-4357/ab72fc },
    }
    

Search for Multimessenger Sources of Gravitational Waves and High-energy Neutrinos with Advanced LIGO during Its First Observing Run, ANTARES, and IceCube

Astrophysical Journal, 870, 134

gravitational waves neutrinos Astrophysics - High Energy Astrophysical Phenomena

| arxiv:1810.10693 | doi:10.3847/1538-4357/aaf21d |

{Astrophysical sources of gravitational waves, such as binary neutron star and black hole mergers or core-collapse supernovae, can drive relativistic outflows, giving rise to non-thermal high- energy emission. High-energy neutrinos are signatures of such outflows. The detection of gravitational waves and high-energy neutrinos from common sources could help establish the connection between the dynamics of the progenitor and the properties of the outflow. We searched for associated emission of gravitational waves and high-energy neutrinos from astrophysical transients with minimal assumptions using data from Advanced LIGO from its first observing run O1, and data from the ANTARES and IceCube neutrino observatories from the same time period. We focused on candidate events whose astrophysical origins could not be determined from a single messenger. We found no significant coincident candidate, which we used to constrain the rate density of astrophysical sources dependent on their gravitational-wave and neutrino emission processes.}
    @article{ 2019ApJ...870..134A,
    
    title = { Search for Multimessenger Sources of Gravitational Waves and High-energy Neutrinos with Advanced LIGO during Its First Observing Run, ANTARES, and IceCube },
    journal = { Astrophysical Journal },
    year = { 2019 },
    month = { January },
    volume = { 870 },
    number = { 2 },
    pages = { 134 },
    doi = { 10.3847/1538-4357/aaf21d },
    }
    

A Fermi Gamma-Ray Burst Monitor Search for Electromagnetic Signals Coincident with Gravitational-wave Candidates in Advanced LIGO's First Observing Run

Astrophysical Journal, 871, 90

gamma-ray burst: general gravitational waves Astrophysics - High Energy Astrophysical Phenomena

| arxiv:1810.02764 | doi:10.3847/1538-4357/aaf726 |

{We present a search for prompt gamma-ray counterparts to compact binary coalescence gravitational wave (GW) candidates from Advanced LIGO{\textquoteright}s first observing run (O1). As demonstrated by the multimessenger observations of GW170817/GRB 170817A, electromagnetic and GW observations provide complementary information about the astrophysical source, and in the case of weaker candidates, may strengthen the case for an astrophysical origin. Here we investigate low-significance GW candidates from the O1 compact binary coalescence searches using the Fermi Gamma-Ray Burst Monitor (GBM), leveraging its all sky and broad energy coverage. Candidates are ranked and compared to background to measure the significance. Those with false alarm rates (FARs) of less than 10$^{-5}$ Hz (about one per day, yielding a total of 81 candidates) are used as the search sample for gamma-ray follow-up. No GW candidates were found to be coincident with gamma-ray transients independently identified by blind searches of the GBM data. In addition, GW candidate event times were followed up by a separate targeted search of GBM data. Among the resulting GBM events, the two with the lowest FARs were the gamma-ray transient GW150914-GBM presented in Connaughton et al. and a solar flare in chance coincidence with a GW candidate.}
    @article{ 2019ApJ...871...90B,
    
    title = { A Fermi Gamma-Ray Burst Monitor Search for Electromagnetic Signals Coincident with Gravitational-wave Candidates in Advanced LIGO's First Observing Run },
    journal = { Astrophysical Journal },
    year = { 2019 },
    month = { January },
    volume = { 871 },
    number = { 1 },
    pages = { 90 },
    doi = { 10.3847/1538-4357/aaf726 },
    }
    

Properties of the Binary Neutron Star Merger GW170817

Physical Review X, 9, 011001

General Relativity and Quantum Cosmology Astrophysics - High Energy Astrophysical Phenomena

| arxiv:1805.11579 | doi:10.1103/PhysRevX.9.011001 |

{On August 17, 2017, the Advanced LIGO and Advanced Virgo gravitational- wave detectors observed a low-mass compact binary inspiral. The initial sky localization of the source of the gravitational-wave signal, GW170817, allowed electromagnetic observatories to identify NGC 4993 as the host galaxy. In this work, we improve initial estimates of the binary's properties, including component masses, spins, and tidal parameters, using the known source location, improved modeling, and recalibrated Virgo data. We extend the range of gravitational-wave frequencies considered down to 23 Hz, compared to 30 Hz in the initial analysis. We also compare results inferred using several signal models, which are more accurate and incorporate additional physical effects as compared to the initial analysis. We improve the localization of the gravitational-wave source to a 90\% credible region of 16 deg$^{2}$ . We find tighter constraints on the masses, spins, and tidal parameters, and continue to find no evidence for nonzero component spins. The component masses are inferred to lie between 1.00 and 1.89 M$_{☉}$ when allowing for large component spins, and to lie between 1.16 and 1.60 M$_{☉}$ (with a total mass 2.73$_{-0.01}$$^{+0.04}$ M$_{☉}$ ) when the spins are restricted to be within the range observed in Galactic binary neutron stars. Using a precessing model and allowing for large component spins, we constrain the dimensionless spins of the components to be less than 0.50 for the primary and 0.61 for the secondary. Under minimal assumptions about the nature of the compact objects, our constraints for the tidal deformability parameter {\ensuremath{\Lambda}} ̃ are (0,630) when we allow for large component spins, and 300$_{-230}$$^{+420}$ (using a 90\% highest posterior density interval) when restricting the magnitude of the component spins, ruling out several equation- of-state models at the 90\% credible level. Finally, with LIGO and GEO600 data, we use a Bayesian analysis to place upper limits on the amplitude and spectral energy density of a possible postmerger signal.

}

    @article{ 2019PhRvX...9a1001A,
    
    title = { Properties of the Binary Neutron Star Merger GW170817 },
    journal = { Physical Review X },
    year = { 2019 },
    month = { January },
    volume = { 9 },
    number = { 1 },
    pages = { 011001 },
    doi = { 10.1103/PhysRevX.9.011001 },
    }
    

Constraining the p -Mode-g -Mode Tidal Instability with GW170817

Physical Review Letters, 122, 061104

Astrophysics - High Energy Astrophysical Phenomena

| arxiv:1808.08676 | doi:10.1103/PhysRevLett.122.061104 |

{We analyze the impact of a proposed tidal instability coupling p modes and g modes within neutron stars on GW170817. This nonresonant instability transfers energy from the orbit of the binary to internal modes of the stars, accelerating the gravitational-wave driven inspiral. We model the impact of this instability on the phasing of the gravitational wave signal using three parameters per star: an overall amplitude, a saturation frequency, and a spectral index. Incorporating these additional parameters, we compute the Bayes factor (ln B$_{!p}$$^{g p g}$ ) comparing our p -g model to a standard one. We find that the observed signal is consistent with waveform models that neglect p -g effects, with ln B$_{!p}$$^{g p g}$ =0.0 3$_{-0.58}$$^{+0.70}$ (maximum a posteriori and 90\% credible region). By injecting simulated signals that do not include p -g effects and recovering them with the p -g model, we show that there is a ≃50 \% probability of obtaining similar ln B$_{!p}$$^{g p g}$ even when p -g effects are absent. We find that the p -g amplitude for 1.4 M$_{☉}$ neutron stars is constrained to less than a few tenths of the theoretical maximum, with maxima a posteriori near one- tenth this maximum and p -g saturation frequency ̃70 Hz . This suggests that there are less than a few hundred excited modes, assuming they all saturate by wave breaking. For comparison, theoretical upper bounds suggest {\ensuremath{\lesssim}}{}10$^{3}$ modes saturate by wave breaking. Thus, the measured constraints only rule out extreme values of the p -g parameters. They also imply that the instability dissipates {\ensuremath{\lesssim}}1 {}0$^{51}$ erg over the entire inspiral, i.e., less than a few percent of the energy radiated as gravitational waves.

}

    @article{ 2019PhRvL.122f1104A,
    
    title = { Constraining the p -Mode-g -Mode Tidal Instability with GW170817 },
    journal = { Physical Review Letters },
    year = { 2019 },
    month = { February },
    volume = { 122 },
    number = { 6 },
    pages = { 061104 },
    doi = { 10.1103/PhysRevLett.122.061104 },
    }
    

Search for Transient Gravitational-wave Signals Associated with Magnetar Bursts during Advanced LIGO's Second Observing Run

Astrophysical Journal, 874, 163

gravitational waves stars: magnetars Astrophysics - High Energy Astrophysical Phenomena

| arxiv:1902.01557 | doi:10.3847/1538-4357/ab0e15 |

{We present the results of a search for short- and intermediate-duration gravitational-wave signals from four magnetar bursts in Advanced LIGO{\textquoteright}s second observing run. We find no evidence of a signal and set upper bounds on the root sum squared of the total dimensionless strain (h $_{rss}$) from incoming intermediate-duration gravitational waves ranging from 1.1 {\texttimes} 10$^{-22}$ at 150 Hz to 4.4 {\texttimes} 10$^{-22}$ at 1550 Hz at 50\% detection efficiency. From the known distance to the magnetar SGR 1806-20 (8.7 kpc), we can place upper bounds on the isotropic gravitational-wave energy of 3.4 {\texttimes} {}10$^{44}$ erg at 150 Hz assuming optimal orientation. This represents an improvement of about a factor of 10 in strain sensitivity from the previous search for such signals, conducted during initial LIGO{\textquoteright}s sixth science run. The short-duration search yielded upper limits of 2.1 {\texttimes} {}10$^{44}$ erg for short white noise bursts, and 2.3 {\texttimes} {}10$^{47}$ erg for 100 ms long ringdowns at 1500 Hz, both at 50\% detection efficiency.}
    @article{ 2019ApJ...874..163A,
    
    title = { Search for Transient Gravitational-wave Signals Associated with Magnetar Bursts during Advanced LIGO's Second Observing Run },
    journal = { Astrophysical Journal },
    year = { 2019 },
    month = { April },
    volume = { 874 },
    number = { 2 },
    pages = { 163 },
    doi = { 10.3847/1538-4357/ab0e15 },
    }
    

Searches for Continuous Gravitational Waves from 15 Supernova Remnants and Fomalhaut b with Advanced LIGO

Astrophysical Journal, 875, 122

gravitational waves ISM: supernova remnants stars: neutron Astrophysics - High Energy Astrophysical Phenomena General Relativity and Quantum Cosmology

| arxiv:1812.11656 | doi:10.3847/1538-4357/ab113b |

{We describe directed searches for continuous gravitational waves (GWs) from 16 well-localized candidate neutron stars, assuming none of the stars has a binary companion. The searches were directed toward 15 supernova remnants and Fomalhaut b, a directly imaged extrasolar planet candidate that has been suggested to be a nearby old neutron star. Each search covered a broad band of frequencies and first and second time derivatives. After coherently integrating spans of data from the first Advanced LIGO observing run of 3.5-53.7 days per search, applying data- based vetoes, and discounting known instrumental artifacts, we found no astrophysical signals. We set upper limits on intrinsic GW strain as strict as 1 {\texttimes} 10$^{-25}$, fiducial neutron star ellipticity as strict as 2 {\texttimes} 10$^{-9}$, and fiducial r-mode amplitude as strict as 3 {\texttimes} 10$^{-8}$.

Any correspondence should be addressed to and .}

    @article{ 2019ApJ...875..122A,
    
    title = { Searches for Continuous Gravitational Waves from 15 Supernova Remnants and Fomalhaut b with Advanced LIGO },
    journal = { Astrophysical Journal },
    year = { 2019 },
    month = { April },
    volume = { 875 },
    number = { 2 },
    pages = { 122 },
    doi = { 10.3847/1538-4357/ab113b },
    }
    

Search for Gravitational Waves from a Long-lived Remnant of the Binary Neutron Star Merger GW170817

Astrophysical Journal, 875, 160

gravitational waves methods: data analysis stars: neutron General Relativity and Quantum Cosmology Astrophysics - High Energy Astrophysical Phenomena

| arxiv:1810.02581 | doi:10.3847/1538-4357/ab0f3d |

{One unanswered question about the binary neutron star coalescence GW170817 is the nature of its post-merger remnant. A previous search for post-merger gravitational waves targeted high- frequency signals from a possible neutron star remnant with a maximum signal duration of 500 s. Here, we revisit the neutron star remnant scenario and focus on longer signal durations, up until the end of the second Advanced LIGO-Virgo observing run, which was 8.5 days after the coalescence of GW170817. The main physical scenario for this emission is the power-law spindown of a massive magnetar-like remnant. We use four independent search algorithms with varying degrees of restrictiveness on the signal waveform and different ways of dealing with noise artefacts. In agreement with theoretical estimates, we find no significant signal candidates. Through simulated signals, we quantify that with the current detector sensitivity, nowhere in the studied parameter space are we sensitive to a signal from more than 1 Mpc away, compared to the actual distance of 40 Mpc. However, this study serves as a prototype for post-merger analyses in future observing runs with expected higher sensitivity.}
    @article{ 2019ApJ...875..160A,
    
    title = { Search for Gravitational Waves from a Long-lived Remnant of the Binary Neutron Star Merger GW170817 },
    journal = { Astrophysical Journal },
    year = { 2019 },
    month = { April },
    volume = { 875 },
    number = { 2 },
    pages = { 160 },
    doi = { 10.3847/1538-4357/ab0f3d },
    }
    

Low-latency Gravitational-wave Alerts for Multimessenger Astronomy during the Second Advanced LIGO and Virgo Observing Run

Astrophysical Journal, 875, 161

gravitational waves methods: data analysis Astrophysics - High Energy Astrophysical Phenomena

| arxiv:1901.03310 | doi:10.3847/1538-4357/ab0e8f |

{Advanced LIGO{\textquoteright}s second observing run (O2), conducted from 2016 November 30 to 2017 August 25, combined with Advanced Virgo{\textquoteright}s first observations in 2017 August, witnessed the birth of gravitational-wave multimessenger astronomy. The first ever gravitational-wave detection from the coalescence of two neutron stars, GW170817, and its gamma-ray counterpart, GRB 170817A, led to an electromagnetic follow-up of the event at an unprecedented scale. Several teams from across the world searched for EM/neutrino counterparts to GW170817, paving the way for the discovery of optical, X-ray, and radio counterparts. In this article, we describe the online identification of gravitational-wave transients and the distribution of gravitational-wave alerts by the LIGO and Virgo collaborations during O2. We also describe the gravitational- wave observables that were sent in the alerts to enable searches for their counterparts. Finally, we give an overview of the online candidate alerts shared with observing partners during O2. Alerts were issued for 14 candidates, 6 of which have been confirmed as gravitational-wave events associated with the merger of black holes or neutron stars. Of the 14 alerts, 8 were issued less than an hour after data acquisition.}
    @article{ 2019ApJ...875..161A,
    
    title = { Low-latency Gravitational-wave Alerts for Multimessenger Astronomy during the Second Advanced LIGO and Virgo Observing Run },
    journal = { Astrophysical Journal },
    year = { 2019 },
    month = { April },
    volume = { 875 },
    number = { 2 },
    pages = { 161 },
    doi = { 10.3847/1538-4357/ab0e8f },
    }
    

All-sky search for long-duration gravitational-wave transients in the second Advanced LIGO observing run

Physical Review D, 99, 104033

General Relativity and Quantum Cosmology

| arxiv:1903.12015 | doi:10.1103/PhysRevD.99.104033 |

{We present the results of a search for long-duration gravitational-wave transients in the data from the Advanced LIGO second observation run; we search for gravitational-wave transients of 2-500 s duration in the 24-2048 Hz frequency band with minimal assumptions about signal properties such as waveform morphologies, polarization, sky location or time of occurrence. Signal families covered by these search algorithms include fallback accretion onto neutron stars, broadband chirps from innermost stable circular orbit waves around rotating black holes, eccentric inspiral-merger-ringdown compact binary coalescence waveforms, and other models. The second observation run totals about 118.3 days of coincident data between November 2016 and August 2017. We find no significant events within the parameter space that we searched, apart from the already- reported binary neutron star merger GW170817. We thus report sensitivity limits on the root-sum-square strain amplitude h$_{rss}$ at 50\% efficiency. These sensitivity estimates are an improvement relative to the first observing run and also done with an enlarged set of gravitational-wave transient waveforms. Overall, the best search sensitivity is h$_{rss}$$^{50 \%}$=2.7 {\texttimes}10$^{-22}$ Hz$^{-1 /2}$ for a millisecond magnetar model. For eccentric compact binary coalescence signals, the search sensitivity reaches h$_{rss}$$^{50 \%}$=9.6 {\texttimes}10$^{-22}$ Hz$^{-1 /2}$ .

}

    @article{ 2019PhRvD..99j4033A,
    
    title = { All-sky search for long-duration gravitational-wave transients in the second Advanced LIGO observing run },
    journal = { Physical Review D },
    year = { 2019 },
    month = { May },
    volume = { 99 },
    number = { 10 },
    pages = { 104033 },
    doi = { 10.1103/PhysRevD.99.104033 },
    }
    

Narrow-band search for gravitational waves from known pulsars using the second LIGO observing run

Physical Review D, 99, 122002

General Relativity and Quantum Cosmology Astrophysics - Instrumentation and Methods for Astrophysics

| arxiv:1902.08442 | doi:10.1103/PhysRevD.99.122002 |

{Isolated spinning neutron stars, asymmetric with respect to their rotation axis, are expected to be sources of continuous gravitational waves. The most sensitive searches for these sources are based on accurate matched filtering techniques that assume the continuous wave to be phase locked with the pulsar beamed emission. While matched filtering maximizes the search sensitivity, a significant signal-to-noise ratio loss will happen in the case of a mismatch between the assumed and the true signal phase evolution. Narrow-band algorithms allow for a small mismatch in the frequency and spin-down values of the pulsar while coherently integrating the entire dataset. In this paper, we describe a narrow-band search using LIGO O2 data for the continuous wave emission of 33 pulsars. No evidence of a continuous wave signal is found, and upper limits on the gravitational wave amplitude over the analyzed frequency and spin-down ranges are computed for each of the targets. In this search, we surpass the spin-down limit, namely, the maximum rotational energy loss due to gravitational waves emission for some of the pulsars already present in the LIGO O1 narrow-band search, such as J 1400 -6325 , J 1813 -1246 , J 1833 -1034 , J 1952 +3252 , and for new targets such as J 0940 -5428 and J 1747 -2809 . For J 1400 -6325 , J 1833 -1034 , and J 1747 -2809 , this is the first time the spin-down limit is surpassed.}
    @article{ 2019PhRvD..99l2002A,
    
    title = { Narrow-band search for gravitational waves from known pulsars using the second LIGO observing run },
    journal = { Physical Review D },
    year = { 2019 },
    month = { June },
    volume = { 99 },
    number = { 12 },
    pages = { 122002 },
    doi = { 10.1103/PhysRevD.99.122002 },
    }
    

Searches for Gravitational Waves from Known Pulsars at Two Harmonics in 2015-2017 LIGO Data

Astrophysical Journal, 879, 10

gravitational waves pulsars: general stars: neutron Astrophysics - High Energy Astrophysical Phenomena General Relativity and Quantum Cosmology

| arxiv:1902.08507 | doi:10.3847/1538-4357/ab20cb |

{We present a search for gravitational waves from 222 pulsars with rotation frequencies {\ensuremath{\gtrsim}}10 Hz. We use advanced LIGO data from its first and second observing runs spanning 2015-2017, which provides the highest-sensitivity gravitational-wave data so far obtained. In this search we target emission from both the l = m = 2 mass quadrupole mode, with a frequency at twice that of the pulsar{\textquoteright}s rotation, and the l = 2, m = 1 mode, with a frequency at the pulsar rotation frequency. The search finds no evidence for gravitational-wave emission from any pulsar at either frequency. For the l = m = 2 mode search, we provide updated upper limits on the gravitational-wave amplitude, mass quadrupole moment, and fiducial ellipticity for 167 pulsars, and the first such limits for a further 55. For 20 young pulsars these results give limits that are below those inferred from the pulsars{\textquoteright} spin-down. For the Crab and Vela pulsars our results constrain gravitational-wave emission to account for less than 0.017\% and 0.18\% of the spin-down luminosity, respectively. For the recycled millisecond pulsar J0711-6830 our limits are only a factor of 1.3 above the spin-down limit, assuming the canonical value of {}10$^{38}$ kg m$^{2}$ for the star{\textquoteright}s moment of inertia, and imply a gravitational-wave-derived upper limit on the star{\textquoteright}s ellipticity of 1.2 {\texttimes} 10$^{-8}$. We also place new limits on the emission amplitude at the rotation frequency of the pulsars.}
    @article{ 2019ApJ...879...10A,
    
    title = { Searches for Gravitational Waves from Known Pulsars at Two Harmonics in 2015-2017 LIGO Data },
    journal = { Astrophysical Journal },
    year = { 2019 },
    month = { July },
    volume = { 879 },
    number = { 1 },
    pages = { 10 },
    doi = { 10.3847/1538-4357/ab20cb },
    }
    

All-sky search for continuous gravitational waves from isolated neutron stars using Advanced LIGO O2 data

Physical Review D, 100, 024004

Astrophysics - High Energy Astrophysical Phenomena General Relativity and Quantum Cosmology

| arxiv:1903.01901 | doi:10.1103/PhysRevD.100.024004 |

{We present results of an all-sky search for continuous gravitational waves (CWs), which can be produced by fast spinning neutron stars with an asymmetry around their rotation axis, using data from the second observing run of the Advanced LIGO detectors. Three different semicoherent methods are used to search in a gravitational-wave frequency band from 20 to 1922 Hz and a first frequency derivative from -1 {\texttimes}10$^{-8}$ to 2 {\texttimes}10$^{-9}$ Hz /s . None of these searches has found clear evidence for a CW signal, so upper limits on the gravitational-wave strain amplitude are calculated, which for this broad range in parameter space are the most sensitive ever achieved.

}

    @article{ 2019PhRvD.100b4004A,
    
    title = { All-sky search for continuous gravitational waves from isolated neutron stars using Advanced LIGO O2 data },
    journal = { Physical Review D },
    year = { 2019 },
    month = { July },
    volume = { 100 },
    number = { 2 },
    pages = { 024004 },
    doi = { 10.1103/PhysRevD.100.024004 },
    }
    

All-sky search for short gravitational-wave bursts in the second Advanced LIGO and Advanced Virgo run

Physical Review D, 100, 024017

Astrophysics - Cosmology and Nongalactic Astrophysics Astrophysics - High Energy Astrophysical Phenomena General Relativity and Quantum Cosmology

| arxiv:1904.08976 | doi:10.1103/PhysRevD.100.024017 |

{We present the results of a search for short-duration gravitational-wave transients in the data from the second observing run of Advanced LIGO and Advanced Virgo. We search for gravitational-wave transients with a duration of milliseconds to approximately one second in the 32-4096 Hz frequency band with minimal assumptions about the signal properties, thus targeting a wide variety of sources. We also perform a matched-filter search for gravitational-wave transients from cosmic string cusps for which the waveform is well modeled. The unmodeled search detected gravitational waves from several binary black hole mergers which have been identified by previous analyses. No other significant events have been found by either the unmodeled search or the cosmic string search. We thus present the search sensitivities for a variety of signal waveforms and report upper limits on the source rate density as a function of the characteristic frequency of the signal. These upper limits are a factor of 3 lower than the first observing run, with a 50\% detection probability for gravitational-wave emissions with energies of ̃10$^{-9}$ M$_{☉}$c$^{2}$ at 153 Hz. For the search dedicated to cosmic string cusps we consider several loop distribution models, and present updated constraints from the same search done in the first observing run.}
    @article{ 2019PhRvD.100b4017A,
    
    title = { All-sky search for short gravitational-wave bursts in the second Advanced LIGO and Advanced Virgo run },
    journal = { Physical Review D },
    year = { 2019 },
    month = { July },
    volume = { 100 },
    number = { 2 },
    pages = { 024017 },
    doi = { 10.1103/PhysRevD.100.024017 },
    }
    

Tests of General Relativity with GW170817

Physical Review Letters, 123, 011102

General Relativity and Quantum Cosmology

| arxiv:1811.00364 | doi:10.1103/PhysRevLett.123.011102 |

{The recent discovery by Advanced LIGO and Advanced Virgo of a gravitational wave signal from a binary neutron star inspiral has enabled tests of general relativity (GR) with this new type of source. This source, for the first time, permits tests of strong-field dynamics of compact binaries in the presence of matter. In this Letter, we place constraints on the dipole radiation and possible deviations from GR in the post-Newtonian coefficients that govern the inspiral regime. Bounds on modified dispersion of gravitational waves are obtained; in combination with information from the observed electromagnetic counterpart we can also constrain effects due to large extra dimensions. Finally, the polarization content of the gravitational wave signal is studied. The results of all tests performed here show good agreement with GR.

}

    @article{ 2019PhRvL.123a1102A,
    
    title = { Tests of General Relativity with GW170817 },
    journal = { Physical Review Letters },
    year = { 2019 },
    month = { July },
    volume = { 123 },
    number = { 1 },
    pages = { 011102 },
    doi = { 10.1103/PhysRevLett.123.011102 },
    }
    

GWTC-1: A Gravitational-Wave Transient Catalog of Compact Binary Mergers Observed by LIGO and Virgo during the First and Second Observing Runs

Physical Review X, 9, 031040

Astrophysics - High Energy Astrophysical Phenomena Astrophysics - Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology

| arxiv:1811.12907 | doi:10.1103/PhysRevX.9.031040 |

{We present the results from three gravitational-wave searches for coalescing compact binaries with component masses above 1 M$_{☉}$ during the first and second observing runs of the advanced gravitational-wave detector network. During the first observing run (O 1 ), from September 12, 2015 to January 19, 2016, gravitational waves from three binary black hole mergers were detected. The second observing run (O 2 ), which ran from November 30, 2016 to August 25, 2017, saw the first detection of gravitational waves from a binary neutron star inspiral, in addition to the observation of gravitational waves from a total of seven binary black hole mergers, four of which we report here for the first time: GW170729, GW170809, GW170818, and GW170823. For all significant gravitational-wave events, we provide estimates of the source properties. The detected binary black holes have total masses between 18.6$_{-0.7}$$^{+3.2}$ M$_{☉}$ and 84.4$_{-11.1}$$^{+15.8}$ M$_{☉}$ and range in distance between 320$_{-110}$$^{+120}$ and 2840$_{-1360}$$^{+1400}$ Mpc . No neutron star-black hole mergers were detected. In addition to highly significant gravitational-wave events, we also provide a list of marginal event candidates with an estimated false-alarm rate less than 1 per 30 days. From these results over the first two observing runs, which include approximately one gravitational-wave detection per 15 days of data searched, we infer merger rates at the 90\% confidence intervals of 110 -3840 Gpc$^{-3}$ y$^{-1}$ for binary neutron stars and 9.7 -101 Gpc$^{-3}$ y$^{-1}$ for binary black holes assuming fixed population distributions and determine a neutron star-black hole merger rate 90\% upper limit of 610 Gpc$^{-3}$ y$^{-1}$ .

}

    @article{ 2019PhRvX...9c1040A,
    
    title = { GWTC-1: A Gravitational-Wave Transient Catalog of Compact Binary Mergers Observed by LIGO and Virgo during the First and Second Observing Runs },
    journal = { Physical Review X },
    year = { 2019 },
    month = { July },
    volume = { 9 },
    number = { 3 },
    pages = { 031040 },
    doi = { 10.1103/PhysRevX.9.031040 },
    }
    

Erratum: {\textquotedblleft}Searches for Gravitational Waves from Known Pulsars at Two Harmonics in 2015-2017 LIGO Data{\textquotedblright} (2019, ApJ, 879, 10)

Astrophysical Journal, 882, 73

| doi:10.3847/1538-4357/ab3231 |

    @article{ 2019ApJ...882...73A,
    
    title = { Erratum: {\textquotedblleft}Searches for Gravitational Waves from Known Pulsars at Two Harmonics in 2015-2017 LIGO Data{\textquotedblright} (2019, ApJ, 879, 10) },
    journal = { Astrophysical Journal },
    year = { 2019 },
    month = { September },
    volume = { 882 },
    number = { 1 },
    pages = { 73 },
    doi = { 10.3847/1538-4357/ab3231 },
    }
    

Binary Black Hole Population Properties Inferred from the First and Second Observing Runs of Advanced LIGO and Advanced Virgo

\apjl, 882, L24

black holes gravitational waves statistical Astrophysics - High Energy Astrophysical Phenomena

| arxiv:1811.12940 | doi:10.3847/2041-8213/ab3800 |

{We present results on the mass, spin, and redshift distributions with phenomenological population models using the 10 binary black hole (BBH) mergers detected in the first and second observing runs completed by Advanced LIGO and Advanced Virgo. We constrain properties of the BBH mass spectrum using models with a range of parameterizations of the BBH mass and spin distributions. We find that the mass distribution of the more massive BH in such binaries is well approximated by models with no more than 1\% of BHs more massive than 45 \{M\}$_{☉ }$ and a power-law index of {\ensuremath{\alpha}} = \{1.3\}$_{-1.7}$$^{+1.4}$ (90\% credibility). We also show that BBHs are unlikely to be composed of BHs with large spins aligned to the orbital angular momentum. Modeling the evolution of the BBH merger rate with redshift, we show that it is flat or increasing with redshift with 93\% probability. Marginalizing over uncertainties in the BBH population, we find robust estimates of the BBH merger rate density of R = \{53.2\}$_{-28.2}$$^{+55.8}$ Gpc$^{-3}$ yr$^{-1}$ (90\% credibility). As the BBH catalog grows in future observing runs, we expect that uncertainties in the population model parameters will shrink, potentially providing insights into the formation of BHs via supernovae, binary interactions of massive stars, stellar cluster dynamics, and the formation history of BHs across cosmic time.}
    @article{ 2019ApJ...882L..24A,
    
    title = { Binary Black Hole Population Properties Inferred from the First and Second Observing Runs of Advanced LIGO and Advanced Virgo },
    journal = { \apjl },
    year = { 2019 },
    month = { September },
    volume = { 882 },
    number = { 2 },
    pages = { L24 },
    doi = { 10.3847/2041-8213/ab3800 },
    }
    

Search for the isotropic stochastic background using data from Advanced LIGO's second observing run

Physical Review D, 100, 061101

General Relativity and Quantum Cosmology

| arxiv:1903.02886 | doi:10.1103/PhysRevD.100.061101 |

{The stochastic gravitational-wave background is a superposition of sources that are either too weak or too numerous to detect individually. In this study, we present the results from a cross-correlation analysis on data from Advanced LIGO's second observing run (O2), which we combine with the results of the first observing run (O1). We do not find evidence for a stochastic background, so we place upper limits on the normalized energy density in gravitational waves at the 95\% credible level of {\ensuremath{\Omega}}$_{GW}$\<6.0 {\texttimes}10$^{-8}$ for a frequency-independent (flat) background and {\ensuremath{\Omega}}$_{GW}$\<4.8 {\texttimes}10$^{-8}$ at 25 Hz for a background of compact binary coalescences. The upper limit improves over the O1 result by a factor of 2.8. Additionally, we place upper limits on the energy density in an isotropic background of scalar- and vector- polarized gravitational waves, and we discuss the implication of these results for models of compact binaries and cosmic string backgrounds. Finally, we present a conservative estimate of the correlated broadband noise due to the magnetic Schumann resonances in O2, based on magnetometer measurements at both the LIGO Hanford and LIGO Livingston observatories. We find that correlated noise is well below the O2 sensitivity.}
    @article{ 2019PhRvD.100f1101A,
    
    title = { Search for the isotropic stochastic background using data from Advanced LIGO's second observing run },
    journal = { Physical Review D },
    year = { 2019 },
    month = { September },
    volume = { 100 },
    number = { 6 },
    pages = { 061101 },
    doi = { 10.1103/PhysRevD.100.061101 },
    }
    

Directional limits on persistent gravitational waves using data from Advanced LIGO's first two observing runs

Physical Review D, 100, 062001

General Relativity and Quantum Cosmology

| arxiv:1903.08844 | doi:10.1103/PhysRevD.100.062001 |

{We perform an unmodeled search for persistent, directional gravitational wave (GW) sources using data from the first and second observing runs of Advanced LIGO. We do not find evidence for any GW signals. We place limits on the broadband GW flux emitted at 25 Hz from point sources with a power law spectrum at F$_{{\ensuremath{\alpha}} ,{\ensuremath{\Theta}}}$\<(0.05 - 25 ){\texttimes}10$^{-8}$ erg cm$^{-2}$ s$^{-1}$ Hz$^{-1}$ and the (normalized) energy density spectrum in GWs at 25 Hz from extended sources at {\ensuremath{\Omega}}$_{{\ensuremath{\alpha} }}$({\ensuremath{\Theta}} )\<(0.19 - 2.89 ){\texttimes}10$^{-8}$ sr$^{-1}$ where {\ensuremath{\alpha}} is the spectral index of the energy density spectrum. These represent improvements of 2.5 - 3 {\texttimes} over previous limits. We also consider point sources emitting GWs at a single frequency, targeting the directions of Sco X-1, SN 1987A, and the Galactic center. The best upper limits on the strain amplitude of a potential source in these three directions range from h$_{0}$\<(3.6 - 4.7 ){\texttimes}10$^{-25}$ , 1.5 {\texttimes} better than previous limits set with the same analysis method. We also report on a marginally significant outlier at 36.06 Hz. This outlier is not consistent with a persistent gravitational-wave source as its significance diminishes when combining all of the available data.

}

    @article{ 2019PhRvD.100f2001A,
    
    title = { Directional limits on persistent gravitational waves using data from Advanced LIGO's first two observing runs },
    journal = { Physical Review D },
    year = { 2019 },
    month = { September },
    volume = { 100 },
    number = { 6 },
    pages = { 062001 },
    doi = { 10.1103/PhysRevD.100.062001 },
    }
    

Search for intermediate mass black hole binaries in the first and second observing runs of the Advanced LIGO and Virgo network

Physical Review D, 100, 064064

Astrophysics - High Energy Astrophysical Phenomena

| arxiv:1907.09384 | doi:10.1103/PhysRevD.100.064064 |

{Gravitational-wave astronomy has been firmly established with the detection of gravitational waves from the merger of ten stellar- mass binary black holes and a neutron star binary. This paper reports on the all-sky search for gravitational waves from intermediate mass black hole binaries in the first and second observing runs of the Advanced LIGO and Virgo network. The search uses three independent algorithms: two based on matched filtering of the data with waveform templates of gravitational- wave signals from compact binaries, and a third, model- independent algorithm that employs no signal model for the incoming signal. No intermediate mass black hole binary event is detected in this search. Consequently, we place upper limits on the merger rate density for a family of intermediate mass black hole binaries. In particular, we choose sources with total masses M =m$_{1}$+m$_{2}${\ensuremath{\in}}[120 ,800 ] M$_{☉}$ and mass ratios q =m$_{2}$/m$_{1}${\ensuremath{\in}}[0.1 ,1.0 ]. For the first time, this calculation is done using numerical relativity waveforms (which include higher modes) as models of the real emitted signal. We place a most stringent upper limit of 0.20 Gpc$^{-3}$ yr$^{-1}$ (in comoving units at the 90\% confidence level) for equal-mass binaries with individual masses m$_{1 ,2}$=100 M$_{☉}$ and dimensionless spins {\ensuremath{\chi}}$_{1 ,2}$=0.8 aligned with the orbital angular momentum of the binary. This improves by a factor of ̃5 that reported after Advanced LIGO's first observing run.}
    @article{ 2019PhRvD.100f4064A,
    
    title = { Search for intermediate mass black hole binaries in the first and second observing runs of the Advanced LIGO and Virgo network },
    journal = { Physical Review D },
    year = { 2019 },
    month = { September },
    volume = { 100 },
    number = { 6 },
    pages = { 064064 },
    doi = { 10.1103/PhysRevD.100.064064 },
    }
    

Search for Eccentric Binary Black Hole Mergers with Advanced LIGO and Advanced Virgo during Their First and Second Observing Runs

Astrophysical Journal, 883, 149

Gravitational waves Elliptical orbits Astrophysical black holes

| doi:10.3847/1538-4357/ab3c2d |

{When formed through dynamical interactions, stellar-mass binary black holes (BBHs) may retain eccentric orbits (e \> 0.1 at 10 Hz) detectable by ground-based gravitational-wave detectors. Eccentricity can therefore be used to differentiate dynamically formed binaries from isolated BBH mergers. Current template- based gravitational-wave searches do not use waveform models associated with eccentric orbits, rendering the search less efficient for eccentric binary systems. Here we present the results of a search for BBH mergers that inspiral in eccentric orbits using data from the first and second observing runs (O1 and O2) of Advanced LIGO and Advanced Virgo. We carried out the search with the coherent WaveBurst algorithm, which uses minimal assumptions on the signal morphology and does not rely on binary waveform templates. We show that it is sensitive to binary mergers with a detection range that is weakly dependent on eccentricity for all bound systems. Our search did not identify any new binary merger candidates. We interpret these results in light of eccentric binary formation models. We rule out formation channels with rates {\ensuremath{\gtrsim}}100 Gpc$^{-3}$ yr$^{-1}$ for e \> 0.1, assuming a black hole mass spectrum with a power-law index {\ensuremath{\lesssim}}2.}
    @article{ 2019ApJ...883..149A,
    
    title = { Search for Eccentric Binary Black Hole Mergers with Advanced LIGO and Advanced Virgo during Their First and Second Observing Runs },
    journal = { Astrophysical Journal },
    year = { 2019 },
    month = { October },
    volume = { 883 },
    number = { 2 },
    pages = { 149 },
    doi = { 10.3847/1538-4357/ab3c2d },
    }
    

Search for Subsolar Mass Ultracompact Binaries in Advanced LIGO's Second Observing Run

Physical Review Letters, 123, 161102

| doi:10.1103/PhysRevLett.123.161102 |

{We present a search for subsolar mass ultracompact objects in data obtained during Advanced LIGO's second observing run. In contrast to a previous search of Advanced LIGO data from the first observing run, this search includes the effects of component spin on the gravitational waveform. We identify no viable gravitational-wave candidates consistent with subsolar mass ultracompact binaries with at least one component between 0.2 M$_{☉}$- 1.0 M$_{☉}$ . We use the null result to constrain the binary merger rate of (0.2 M$_{☉}$ , 0.2 M$_{☉}$ ) binaries to be less than 3.7 {\texttimes}{}10$^{5}$ Gpc$^{-3}$ yr$^{-1}$ and the binary merger rate of (1.0 M$_{☉}$ , 1.0 M$_{☉}$ ) binaries to be less than 5.2 {\texttimes}{}10$^{3}$ Gpc$^{-3}$ yr$^{-1}$ . Subsolar mass ultracompact objects are not expected to form via known stellar evolution channels, though it has been suggested that primordial density fluctuations or particle dark matter with cooling mechanisms and/or nuclear interactions could form black holes with subsolar masses. Assuming a particular primordial black hole (PBH) formation model, we constrain a population of merging 0.2 M$_{☉}$ black holes to account for less than 16\% of the dark matter density and a population of merging 1.0 M$_{☉}$ black holes to account for less than 2\% of the dark matter density. We discuss how constraints on the merger rate and dark matter fraction may be extended to arbitrary black hole population models that predict subsolar mass binaries.

}

    @article{ 2019PhRvL.123p1102A,
    
    title = { Search for Subsolar Mass Ultracompact Binaries in Advanced LIGO's Second Observing Run },
    journal = { Physical Review Letters },
    year = { 2019 },
    month = { October },
    volume = { 123 },
    number = { 16 },
    pages = { 161102 },
    doi = { 10.1103/PhysRevLett.123.161102 },
    }
    

First Search for Nontensorial Gravitational Waves from Known Pulsars

Physical Review Letters, 120, 031104

General Relativity and Quantum Cosmology

| arxiv:1709.09203 | doi:10.1103/PhysRevLett.120.031104 |

{We present results from the first directed search for nontensorial gravitational waves. While general relativity allows for tensorial (plus and cross) modes only, a generic metric theory may, in principle, predict waves with up to six different polarizations. This analysis is sensitive to continuous signals of scalar, vector, or tensor polarizations, and does not rely on any specific theory of gravity. After searching data from the first observation run of the advanced LIGO detectors for signals at twice the rotational frequency of 200 known pulsars, we find no evidence of gravitational waves of any polarization. We report the first upper limits for scalar and vector strains, finding values comparable in magnitude to previously published limits for tensor strain. Our results may be translated into constraints on specific alternative theories of gravity.

}

    @article{ 2018PhRvL.120c1104A,
    
    title = { First Search for Nontensorial Gravitational Waves from Known Pulsars },
    journal = { Physical Review Letters },
    year = { 2018 },
    month = { January },
    volume = { 120 },
    number = { 3 },
    pages = { 031104 },
    doi = { 10.1103/PhysRevLett.120.031104 },
    }
    

All-sky search for long-duration gravitational wave transients in the first Advanced LIGO observing run

Classical and Quantum Gravity, 35, 065009

General Relativity and Quantum Cosmology Astrophysics - High Energy Astrophysical Phenomena

| arxiv:1711.06843 | doi:10.1088/1361-6382/aaab76 |

{We present the results of a search for long-duration gravitational wave transients in the data of the LIGO Hanford and LIGO Livingston second generation detectors between \textbackslashnewcommand\{\textbackslashOOneStart\}\{12 \raisebox{-0.5ex}\textasciitildeSeptember \raisebox{-0.5ex}\textasciitilde2015\} \textbackslashnewcommand\ {\textbackslashOOneStartShort\}\{September \raisebox{-0.5ex}\textasciitilde2015\} \textbackslashOOneStartShort and \textbackslashnewcommand\{\text backslashOOneStop\}\{19\raisebox{-0.5ex}\textasciitilde January \raisebox{-0.5ex}\textasciitilde2016\} \textbackslashnewcommand\ {\textbackslashOOneStopShort\}\{January\raisebox{-0.5ex}\textasc iitilde 2016\} \textbackslashOOneStopShort , with a total observational time of \textbackslashnewcommand\{\textbackslashOO neLivetime\}\{49\raisebox{-0.5ex}\textasciitilded\} \textbackslashOOneLivetime . The search targets gravitational wave transients of 10-500{\,}s duration in a frequency band of 24-2048 Hz, with minimal assumptions about the signal waveform, polarization, source direction, or time of occurrence. No significant events were observed. As a result we set 90\% confidence upper limits on the rate of long-duration gravitational wave transients for different types of gravitational wave signals. We also show that the search is sensitive to sources in the Galaxy emitting at least{\,}{\,}̃10$^{-8}$ \textbackslashnewcommand\{\textbackslashmsuncd\}\{M$_{☉ c\^2}$\} \textbackslashnewcommand\{\textbackslashmsun\}\{M$_{☉}$\} \{\textbackslashmsuncd\} in gravitational waves.

}

    @article{ 2018CQGra..35f5009A,
    
    title = { All-sky search for long-duration gravitational wave transients in the first Advanced LIGO observing run },
    journal = { Classical and Quantum Gravity },
    year = { 2018 },
    month = { March },
    volume = { 35 },
    number = { 6 },
    pages = { 065009 },
    doi = { 10.1088/1361-6382/aaab76 },
    }
    

GW170817: Implications for the Stochastic Gravitational-Wave Background from Compact Binary Coalescences

Physical Review Letters, 120, 091101

General Relativity and Quantum Cosmology

| arxiv:1710.05837 | doi:10.1103/PhysRevLett.120.091101 |

{The LIGO Scientific and Virgo Collaborations have announced the event GW170817, the first detection of gravitational waves from the coalescence of two neutron stars. The merger rate of binary neutron stars estimated from this event suggests that distant, unresolvable binary neutron stars create a significant astrophysical stochastic gravitational-wave background. The binary neutron star component will add to the contribution from binary black holes, increasing the amplitude of the total astrophysical background relative to previous expectations. In the Advanced LIGO-Virgo frequency band most sensitive to stochastic backgrounds (near 25 Hz), we predict a total astrophysical background with amplitude {\ensuremath{\Omega}}$_{GW}$(f =25 Hz )=1. 8$_{-1.3}$$^{+2.7}${\texttimes}10$^{-9}$ with 90\% confidence, compared with {\ensuremath{\Omega}}$_{GW}$(f =25 Hz )=1. 1$_{-0.7}$$^{+1.2}${\texttimes}10$^{-9}$ from binary black holes alone. Assuming the most probable rate for compact binary mergers, we find that the total background may be detectable with a signal-to-noise-ratio of 3 after 40 months of total observation time, based on the expected timeline for Advanced LIGO and Virgo to reach their design sensitivity.

}

    @article{ 2018PhRvL.120i1101A,
    
    title = { GW170817: Implications for the Stochastic Gravitational-Wave Background from Compact Binary Coalescences },
    journal = { Physical Review Letters },
    year = { 2018 },
    month = { March },
    volume = { 120 },
    number = { 9 },
    pages = { 091101 },
    doi = { 10.1103/PhysRevLett.120.091101 },
    }
    

Prospects for observing and localizing gravitational-wave transients with Advanced LIGO, Advanced Virgo and KAGRA

Living Reviews in Relativity, 21, 3

Gravitational waves Gravitational-wave detectors Electromagnetic counterparts Data analysis General Relativity and Quantum Cosmology Astrophysics - High Energy Astrophysical Phenomena

| arxiv:1304.0670 | doi:10.1007/s41114-018-0012-9 |

{We present possible observing scenarios for the Advanced LIGO, Advanced Virgo and KAGRA gravitational-wave detectors over the next decade, with the intention of providing information to the astronomy community to facilitate planning for multi-messenger astronomy with gravitational waves. We estimate the sensitivity of the network to transient gravitational-wave signals, and study the capability of the network to determine the sky location of the source. We report our findings for gravitational-wave transients, with particular focus on gravitational-wave signals from the inspiral of binary neutron star systems, which are the most promising targets for multi- messenger astronomy. The ability to localize the sources of the detected signals depends on the geographical distribution of the detectors and their relative sensitivity, and 90\% credible regions can be as large as thousands of square degrees when only two sensitive detectors are operational. Determining the sky position of a significant fraction of detected signals to areas of 5-20 deg\^2 requires at least three detectors of sensitivity within a factor of ̃ 2 of each other and with a broad frequency bandwidth. When all detectors, including KAGRA and the third LIGO detector in India, reach design sensitivity, a significant fraction of gravitational-wave signals will be localized to a few square degrees by gravitational-wave observations alone.}
    @article{ 2018LRR....21....3A,
    
    title = { Prospects for observing and localizing gravitational-wave transients with Advanced LIGO, Advanced Virgo and KAGRA },
    journal = { Living Reviews in Relativity },
    year = { 2018 },
    month = { April },
    volume = { 21 },
    number = { 1 },
    pages = { 3 },
    doi = { 10.1007/s41114-018-0012-9 },
    }
    

Constraints on cosmic strings using data from the first Advanced LIGO observing run

Physical Review D, 97, 102002

General Relativity and Quantum Cosmology Astrophysics - Cosmology and Nongalactic Astrophysics

| arxiv:1712.01168 | doi:10.1103/PhysRevD.97.102002 |

{Cosmic strings are topological defects which can be formed in grand unified theory scale phase transitions in the early universe. They are also predicted to form in the context of string theory. The main mechanism for a network of Nambu-Goto cosmic strings to lose energy is through the production of loops and the subsequent emission of gravitational waves, thus offering an experimental signature for the existence of cosmic strings. Here we report on the analysis conducted to specifically search for gravitational-wave bursts from cosmic string loops in the data of Advanced LIGO 2015-2016 observing run (O1). No evidence of such signals was found in the data, and as a result we set upper limits on the cosmic string parameters for three recent loop distribution models. In this paper, we initially derive constraints on the string tension G {\ensuremath{\mu}} and the intercommutation probability, using not only the burst analysis performed on the O1 data set but also results from the previously published LIGO stochastic O1 analysis, pulsar timing arrays, cosmic microwave background and big-bang nucleosynthesis experiments. We show that these data sets are complementary in that they probe gravitational waves produced by cosmic string loops during very different epochs. Finally, we show that the data sets exclude large parts of the parameter space of the three loop distribution models we consider.

}

    @article{ 2018PhRvD..97j2002A,
    
    title = { Constraints on cosmic strings using data from the first Advanced LIGO observing run },
    journal = { Physical Review D },
    year = { 2018 },
    month = { May },
    volume = { 97 },
    number = { 10 },
    pages = { 102002 },
    doi = { 10.1103/PhysRevD.97.102002 },
    }
    

Full band all-sky search for periodic gravitational waves in the O1 LIGO data

Physical Review D, 97, 102003

General Relativity and Quantum Cosmology

| arxiv:1802.05241 | doi:10.1103/PhysRevD.97.102003 |

{We report on a new all-sky search for periodic gravitational waves in the frequency band 475-2000 Hz and with a frequency time derivative in the range of [-1.0 ,+0.1 ] {\texttimes}1 0$^{-8}$ Hz /s . Potential signals could be produced by a nearby spinning and slightly nonaxisymmetric isolated neutron star in our Galaxy. This search uses the data from Advanced LIGO's first observational run O1. No gravitational-wave signals were observed, and upper limits were placed on their strengths. For completeness, results from the separately published low- frequency search 20-475 Hz are included as well. Our lowest upper limit on worst-case (linearly polarized) strain amplitude h$_{0}$ is ̃4 {\texttimes}1 0$^{-25}$ near 170 Hz, while at the high end of our frequency range, we achieve a worst-case upper limit of 1.3 {\texttimes}1 0$^{-24}$. For a circularly polarized source (most favorable orientation), the smallest upper limit obtained is ̃1.5 {\texttimes}1 0$^{-25}$.

}

    @article{ 2018PhRvD..97j2003A,
    
    title = { Full band all-sky search for periodic gravitational waves in the O1 LIGO data },
    journal = { Physical Review D },
    year = { 2018 },
    month = { May },
    volume = { 97 },
    number = { 10 },
    pages = { 102003 },
    doi = { 10.1103/PhysRevD.97.102003 },
    }
    

Search for Tensor, Vector, and Scalar Polarizations in the Stochastic Gravitational-Wave Background

Physical Review Letters, 120, 201102

General Relativity and Quantum Cosmology Astrophysics - Cosmology and Nongalactic Astrophysics

| arxiv:1802.10194 | doi:10.1103/PhysRevLett.120.201102 |

{The detection of gravitational waves with Advanced LIGO and Advanced Virgo has enabled novel tests of general relativity, including direct study of the polarization of gravitational waves. While general relativity allows for only two tensor gravitational-wave polarizations, general metric theories can additionally predict two vector and two scalar polarizations. The polarization of gravitational waves is encoded in the spectral shape of the stochastic gravitational-wave background, formed by the superposition of cosmological and individually unresolved astrophysical sources. Using data recorded by Advanced LIGO during its first observing run, we search for a stochastic background of generically polarized gravitational waves. We find no evidence for a background of any polarization, and place the first direct bounds on the contributions of vector and scalar polarizations to the stochastic background. Under log-uniform priors for the energy in each polarization, we limit the energy densities of tensor, vector, and scalar modes at 95\% credibility to {\ensuremath{\Omega}}$_{0}$$^{T}$\<5.58 {\texttimes}10$^{-8}$ , {\ensuremath{\Omega}}$_{0}$$^{V}$\<6.35 {\texttimes}10$^{-8}$ , and {\ensuremath{\Omega}}$_{0}$$^{S}$\<1.08 {\texttimes}10$^{-7}$ at a reference frequency f$_{0}$=25 Hz .

}

    @article{ 2018PhRvL.120t1102A,
    
    title = { Search for Tensor, Vector, and Scalar Polarizations in the Stochastic Gravitational-Wave Background },
    journal = { Physical Review Letters },
    year = { 2018 },
    month = { May },
    volume = { 120 },
    number = { 20 },
    pages = { 201102 },
    doi = { 10.1103/PhysRevLett.120.201102 },
    }
    

GW170817: Measurements of Neutron Star Radii and Equation of State

Physical Review Letters, 121, 161101

General Relativity and Quantum Cosmology Astrophysics - High Energy Astrophysical Phenomena

| arxiv:1805.11581 | doi:10.1103/PhysRevLett.121.161101 |

{On 17 August 2017, the LIGO and Virgo observatories made the first direct detection of gravitational waves from the coalescence of a neutron star binary system. The detection of this gravitational-wave signal, GW170817, offers a novel opportunity to directly probe the properties of matter at the extreme conditions found in the interior of these stars. The initial, minimal-assumption analysis of the LIGO and Virgo data placed constraints on the tidal effects of the coalescing bodies, which were then translated to constraints on neutron star radii. Here, we expand upon previous analyses by working under the hypothesis that both bodies were neutron stars that are described by the same equation of state and have spins within the range observed in Galactic binary neutron stars. Our analysis employs two methods: the use of equation-of-state-insensitive relations between various macroscopic properties of the neutron stars and the use of an efficient parametrization of the defining function p ({\ensuremath{\rho}} ) of the equation of state itself. From the LIGO and Virgo data alone and the first method, we measure the two neutron star radii as R$_{1}$=10.8$_{-1.7}$$^{+2.0}$ km for the heavier star and R$_{2}$=10.7$_{-1.5}$$^{+2.1}$ km for the lighter star at the 90\% credible level. If we additionally require that the equation of state supports neutron stars with masses larger than 1.97 M$_{☉}$ as required from electromagnetic observations and employ the equation-of-state parametrization, we further constrain R$_{1}$=11.9$_{-1.4}$$^{+1.4}$ km and R$_{2}$=11.9$_{-1.4}$$^{+1.4}$ km at the 90\% credible level. Finally, we obtain constraints on p ({\ensuremath{\rho}} ) at supranuclear densities, with pressure at twice nuclear saturation density measured at 3.5$_{-1.7}$$^{+2.7}${\texttimes}{}10$^{34}$ dyn cm$^{-2}$ at the 90\% level.

}

    @article{ 2018PhRvL.121p1101A,
    
    title = { GW170817: Measurements of Neutron Star Radii and Equation of State },
    journal = { Physical Review Letters },
    year = { 2018 },
    month = { October },
    volume = { 121 },
    number = { 16 },
    pages = { 161101 },
    doi = { 10.1103/PhysRevLett.121.161101 },
    }
    

transientlunatic/minke: Luce Bay

{Williams}, Daniel and {anonymouscommitter}

| doi:10.5281/zenodo.1699336 |

    @article{ 2018zndo...1699336W,
    author =  {Williams} and   Daniel and {anonymouscommitter},
    title = { transientlunatic/minke: Luce Bay },
    year = { 2018 },
    month = { November },
    doi = { 10.5281/zenodo.1699336 },
    }
    

Search for Subsolar-Mass Ultracompact Binaries in Advanced LIGO's First Observing Run

Physical Review Letters, 121, 231103

Astrophysics - Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology

| arxiv:1808.04771 | doi:10.1103/PhysRevLett.121.231103 |

{We present the first Advanced LIGO and Advanced Virgo search for ultracompact binary systems with component masses between 0.2 M$_{☉}$- 1.0 M$_{☉}$ using data taken between September 12, 2015 and January 19, 2016. We find no viable gravitational wave candidates. Our null result constrains the coalescence rate of monochromatic (delta function) distributions of nonspinning (0.2 M$_{☉}$ , 0.2 M$_{☉}$ ) ultracompact binaries to be less than 1.0 {\texttimes}{}10$^{6}$ Gpc$^{-3}$ yr$^{-1}$ and the coalescence rate of a similar distribution of (1.0 M$_{☉}$ , 1.0 M$_{☉}$ ) ultracompact binaries to be less than 1.9 {\texttimes}{}10$^{4}$ Gpc$^{-3}$ yr$^{-1}$ (at 90\% confidence). Neither black holes nor neutron stars are expected to form below ̃1 M$_{☉}$ through conventional stellar evolution, though it has been proposed that similarly low mass black holes could be formed primordially through density fluctuations in the early Universe and contribute to the dark matter density. The interpretation of our constraints in the primordial black hole dark matter paradigm is highly model dependent; however, under a particular primordial black hole binary formation scenario we constrain monochromatic primordial black hole populations of 0.2 M$_{☉}$ to be less than 33\% of the total dark matter density and monochromatic populations of 1.0 M$_{☉}$ to be less than 5\% of the dark matter density. The latter strengthens the presently placed bounds from microlensing surveys of massive compact halo objects (MACHOs) provided by the MACHO and EROS Collaborations.

}

    @article{ 2018PhRvL.121w1103A,
    
    title = { Search for Subsolar-Mass Ultracompact Binaries in Advanced LIGO's First Observing Run },
    journal = { Physical Review Letters },
    year = { 2018 },
    month = { December },
    volume = { 121 },
    number = { 23 },
    pages = { 231103 },
    doi = { 10.1103/PhysRevLett.121.231103 },
    }
    

Constraints On Short, Hard Gamma-Ray Burst Beaming Angles From Gravitational Wave Observations

Daniel Williams, James Clark, Andrew Williamson, Ik Siong Heng

Astrophysical Journal, 858, 2

gamma-ray burst: general gravitational waves

| arxiv:1712.02585 | doi:10.3847/1538-4357/aab847 | data:10.5281/zenodo.1066019 |

The first detection of a binary neutron star merger, GW170817, and an associated short gamma-ray burst confirmed that neutron star mergers are responsible for at least some of these bursts. The prompt gamma ray emission from these events is thought to be highly relativistically beamed. We present a method for inferring limits on the extent of this beaming by comparing the number of short gamma-ray bursts observed electromagnetically to the number of neutron star binary mergers detected in gravitational waves. We demonstrate that an observing run comparable to the expected Advanced LIGO 2016--2017 run would be capable of placing limits on the beaming angle of approximately θ∈(2.88∘,14.15∘), given one binary neutron star detection. We anticipate that after a year of observations with Advanced LIGO at design sensitivity in 2020 these constraints would improve to θ∈(8.10∘,14.95∘).
    @article{ 2017arXiv171202585W,
    author = { Daniel Williams } and { James Clark } and { Andrew Williamson } and { Ik Siong Heng },
    title = { Constraints On Short, Hard Gamma-Ray Burst Beaming Angles From Gravitational Wave Observations },
    journal = { Astrophysical Journal },
    year = { 2018 },
    volume = { 858 },
    doi = { 10.3847/1538-4357/aab847 },
    }
    

All-sky search for short gravitational-wave bursts in the first Advanced LIGO run

Physical Review D, 95, 042003

General Relativity and Quantum Cosmology Astrophysics - High Energy Astrophysical Phenomena

| arxiv:1611.02972 | doi:10.1103/PhysRevD.95.042003 |

{We present the results from an all-sky search for short-duration gravitational waves in the data of the first run of the Advanced LIGO detectors between September 2015 and January 2016. The search algorithms use minimal assumptions on the signal morphology, so they are sensitive to a wide range of sources emitting gravitational waves. The analyses target transient signals with duration ranging from milliseconds to seconds over the frequency band of 32 to 4096 Hz. The first observed gravitational-wave event, GW150914, has been detected with high confidence in this search; the other known gravitational-wave event, GW151226, falls below the search's sensitivity. Besides GW150914, all of the search results are consistent with the expected rate of accidental noise coincidences. Finally, we estimate rate-density limits for a broad range of non-binary- black-hole transient gravitational-wave sources as a function of their gravitational radiation emission energy and their characteristic frequency. These rate-density upper limits are stricter than those previously published by an order of magnitude.

}

    @article{ 2017PhRvD..95d2003A,
    
    title = { All-sky search for short gravitational-wave bursts in the first Advanced LIGO run },
    journal = { Physical Review D },
    year = { 2017 },
    month = { February },
    volume = { 95 },
    number = { 4 },
    pages = { 042003 },
    doi = { 10.1103/PhysRevD.95.042003 },
    }
    

Upper Limits on the Stochastic Gravitational-Wave Background from Advanced LIGO's First Observing Run

Physical Review Letters, 118, 121101

General Relativity and Quantum Cosmology Astrophysics - Cosmology and Nongalactic Astrophysics Astrophysics - High Energy Astrophysical Phenomena

| arxiv:1612.02029 | doi:10.1103/PhysRevLett.118.121101 |

{A wide variety of astrophysical and cosmological sources are expected to contribute to a stochastic gravitational-wave background. Following the observations of GW150914 and GW151226, the rate and mass of coalescing binary black holes appear to be greater than many previous expectations. As a result, the stochastic background from unresolved compact binary coalescences is expected to be particularly loud. We perform a search for the isotropic stochastic gravitational-wave background using data from Advanced Laser Interferometer Gravitational Wave Observatory's (aLIGO) first observing run. The data display no evidence of a stochastic gravitational-wave signal. We constrain the dimensionless energy density of gravitational waves to be {\ensuremath{\Omega}}$_{0}$\<1.7 {\texttimes}10$^{-7}$ with 95\% confidence, assuming a flat energy density spectrum in the most sensitive part of the LIGO band (20-86 Hz). This is a factor of ̃33 times more sensitive than previous measurements. We also constrain arbitrary power-law spectra. Finally, we investigate the implications of this search for the background of binary black holes using an astrophysical model for the background.

}

    @article{ 2017PhRvL.118l1101A,
    
    title = { Upper Limits on the Stochastic Gravitational-Wave Background from Advanced LIGO's First Observing Run },
    journal = { Physical Review Letters },
    year = { 2017 },
    month = { March },
    volume = { 118 },
    number = { 12 },
    pages = { 121101 },
    doi = { 10.1103/PhysRevLett.118.121101 },
    }
    

Directional Limits on Persistent Gravitational Waves from Advanced LIGO's First Observing Run

Physical Review Letters, 118, 121102

General Relativity and Quantum Cosmology Astrophysics - Cosmology and Nongalactic Astrophysics Astrophysics - High Energy Astrophysical Phenomena Astrophysics - Instrumentation and Methods for Astrophysics

| arxiv:1612.02030 | doi:10.1103/PhysRevLett.118.121102 |

{We employ gravitational-wave radiometry to map the stochastic gravitational wave background expected from a variety of contributing mechanisms and test the assumption of isotropy using data from the Advanced Laser Interferometer Gravitational Wave Observatory's (aLIGO) first observing run. We also search for persistent gravitational waves from point sources with only minimal assumptions over the 20-1726 Hz frequency band. Finding no evidence of gravitational waves from either point sources or a stochastic background, we set limits at 90\% confidence. For broadband point sources, we report upper limits on the gravitational wave energy flux per unit frequency in the range F$_{{\ensuremath{\alpha}} ,{\ensuremath{\Theta}}}$(f )\<(0.1 - 56 ){\texttimes}10$^{-8}$ erg cm$^{-2}$ s$^{-1}$ Hz$^{-1}$(f /25 Hz )$^{{\ensuremath{\alpha}} -1}$ depending on the sky location {\ensuremath{\Theta}} and the spectral power index {\ensuremath{\alpha}} . For extended sources, we report upper limits on the fractional gravitational wave energy density required to close the Universe of {\ensuremath{\Omega}} (f ,{\ensuremath{\Theta}} )\<(0.39 - 7.6 ){\texttimes}10$^{-8}$ sr$^{-1}$(f /25 Hz )$^{{\ensuremath{\alpha}}}$ depending on {\ensuremath{\Theta}} and {\ensuremath{\alpha}} . Directed searches for narrowband gravitational waves from astrophysically interesting objects (Scorpius X-1, Supernova 1987 A, and the Galactic Center) yield median frequency-dependent limits on strain amplitude of h$_{0}$\<(6.7 ,5.5 , and 7.0 ){\texttimes}10$^{-25}$ , respectively, at the most sensitive detector frequencies between 130-175 Hz. This represents a mean improvement of a factor of 2 across the band compared to previous searches of this kind for these sky locations, considering the different quantities of strain constrained in each case.

}

    @article{ 2017PhRvL.118l1102A,
    
    title = { Directional Limits on Persistent Gravitational Waves from Advanced LIGO's First Observing Run },
    journal = { Physical Review Letters },
    year = { 2017 },
    month = { March },
    volume = { 118 },
    number = { 12 },
    pages = { 121102 },
    doi = { 10.1103/PhysRevLett.118.121102 },
    }
    

First Search for Gravitational Waves from Known Pulsars with Advanced LIGO

Astrophysical Journal, 839, 12

gravitational waves pulsars: general Astrophysics - High Energy Astrophysical Phenomena General Relativity and Quantum Cosmology

| arxiv:1701.07709 | doi:10.3847/1538-4357/aa677f |

{We present the result of searches for gravitational waves from 200 pulsars using data from the first observing run of the Advanced LIGO detectors. We find no significant evidence for a gravitational-wave signal from any of these pulsars, but we are able to set the most constraining upper limits yet on their gravitational-wave amplitudes and ellipticities. For eight of these pulsars, our upper limits give bounds that are improvements over the indirect spin-down limit values. For another 32, we are within a factor of 10 of the spin-down limit, and it is likely that some of these will be reachable in future runs of the advanced detector. Taken as a whole, these new results improve on previous limits by more than a factor of two.}
    @article{ 2017ApJ...839...12A,
    
    title = { First Search for Gravitational Waves from Known Pulsars with Advanced LIGO },
    journal = { Astrophysical Journal },
    year = { 2017 },
    month = { April },
    volume = { 839 },
    number = { 1 },
    pages = { 12 },
    doi = { 10.3847/1538-4357/aa677f },
    }
    

Effects of waveform model systematics on the interpretation of GW150914

Classical and Quantum Gravity, 34, 104002

General Relativity and Quantum Cosmology Astrophysics - High Energy Astrophysical Phenomena

| arxiv:1611.07531 | doi:10.1088/1361-6382/aa6854 |

{Parameter estimates of GW150914 were obtained using Bayesian inference, based on three semi-analytic waveform models for binary black hole coalescences. These waveform models differ from each other in their treatment of black hole spins, and all three models make some simplifying assumptions, notably to neglect sub- dominant waveform harmonic modes and orbital eccentricity. Furthermore, while the models are calibrated to agree with waveforms obtained by full numerical solutions of Einstein{\textquoteright}s equations, any such calibration is accurate only to some non-zero tolerance and is limited by the accuracy of the underlying phenomenology, availability, quality, and parameter-space coverage of numerical simulations. This paper complements the original analyses of GW150914 with an investigation of the effects of possible systematic errors in the waveform models on estimates of its source parameters. To test for systematic errors we repeat the original Bayesian analysis on mock signals from numerical simulations of a series of binary configurations with parameters similar to those found for GW150914. Overall, we find no evidence for a systematic bias relative to the statistical error of the original parameter recovery of GW150914 due to modeling approximations or modeling inaccuracies. However, parameter biases are found to occur for some configurations disfavored by the data of GW150914: for binaries inclined edge-on to the detector over a small range of choices of polarization angles, and also for eccentricities greater than{\,}{\,}̃0.05. For signals with higher signal-to- noise ratio than GW150914, or in other regions of the binary parameter space (lower masses, larger mass ratios, or higher spins), we expect that systematic errors in current waveform models may impact gravitational-wave measurements, making more accurate models desirable for future observations.

}

    @article{ 2017CQGra..34j4002A,
    
    title = { Effects of waveform model systematics on the interpretation of GW150914 },
    journal = { Classical and Quantum Gravity },
    year = { 2017 },
    month = { May },
    volume = { 34 },
    number = { 10 },
    pages = { 104002 },
    doi = { 10.1088/1361-6382/aa6854 },
    }
    

Search for Gravitational Waves Associated with Gamma-Ray Bursts during the First Advanced LIGO Observing Run and Implications for the Origin of GRB 150906B

Astrophysical Journal, 841, 89

binaries: close gamma-ray burst: general gravitational waves Astrophysics - High Energy Astrophysical Phenomena General Relativity and Quantum Cosmology

| arxiv:1611.07947 | doi:10.3847/1538-4357/aa6c47 |

{We present the results of the search for gravitational waves (GWs) associated with {\ensuremath{\gamma}}-ray bursts detected during the first observing run of the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO). We find no evidence of a GW signal for any of the 41 {\ensuremath{\gamma}}-ray bursts for which LIGO data are available with sufficient duration. For all {\ensuremath{\gamma}}-ray bursts, we place lower bounds on the distance to the source using the optimistic assumption that GWs with an energy of \{10\}$^{-2}$\{M\}$_{☉ }$\{c\}$^{2}$ were emitted within the 16-500 Hz band, and we find a median 90\% confidence limit of 71 Mpc at 150 Hz. For the subset of 19 short/hard {\ensuremath{\gamma}}-ray bursts, we place lower bounds on distance with a median 90\% confidence limit of 90 Mpc for binary neutron star (BNS) coalescences, and 150 and 139 Mpc for neutron star-black hole coalescences with spins aligned to the orbital angular momentum and in a generic configuration, respectively. These are the highest distance limits ever achieved by GW searches. We also discuss in detail the results of the search for GWs associated with GRB 150906B, an event that was localized by the InterPlanetary Network near the local galaxy NGC 3313, which is at a luminosity distance of 54 Mpc (z = 0.0124). Assuming the {\ensuremath{\gamma}}-ray emission is beamed with a jet half-opening angle {\ensuremath{\leq}}slant 30\^\textbackslashcirc , we exclude a BNS and a neutron star- black hole in NGC 3313 as the progenitor of this event with confidence \>99\%. Further, we exclude such progenitors up to a distance of 102 Mpc and 170 Mpc, respectively.}
    @article{ 2017ApJ...841...89A,
    
    title = { Search for Gravitational Waves Associated with Gamma-Ray Bursts during the First Advanced LIGO Observing Run and Implications for the Origin of GRB 150906B },
    journal = { Astrophysical Journal },
    year = { 2017 },
    month = { June },
    volume = { 841 },
    number = { 2 },
    pages = { 89 },
    doi = { 10.3847/1538-4357/aa6c47 },
    }
    

Search for gravitational waves from Scorpius X-1 in the first Advanced LIGO observing run with a hidden Markov model

Physical Review D, 95, 122003

General Relativity and Quantum Cosmology

| arxiv:1704.03719 | doi:10.1103/PhysRevD.95.122003 |

{Results are presented from a semicoherent search for continuous gravitational waves from the brightest low-mass X-ray binary, Scorpius X-1, using data collected during the first Advanced LIGO observing run. The search combines a frequency domain matched filter (Bessel-weighted F -statistic) with a hidden Markov model to track wandering of the neutron star spin frequency. No evidence of gravitational waves is found in the frequency range 60-650 Hz. Frequentist 95\% confidence strain upper limits, h$_{0}$$^{95 \%}$=4.0 {\texttimes}1 0$^{-25}$, 8.3 {\texttimes}1 0$^{-25}$, and 3.0 {\texttimes}1 0$^{-25}$ for electromagnetically restricted source orientation, unknown polarization, and circular polarization, respectively, are reported at 106 Hz. They are {\ensuremath{\leq}}10 times higher than the theoretical torque-balance limit at 106 Hz.

}

    @article{ 2017PhRvD..95l2003A,
    
    title = { Search for gravitational waves from Scorpius X-1 in the first Advanced LIGO observing run with a hidden Markov model },
    journal = { Physical Review D },
    year = { 2017 },
    month = { June },
    volume = { 95 },
    number = { 12 },
    pages = { 122003 },
    doi = { 10.1103/PhysRevD.95.122003 },
    }
    

GW170104: Observation of a 50-Solar-Mass Binary Black Hole Coalescence at Redshift 0.2

Physical Review Letters, 118, 221101

General Relativity and Quantum Cosmology Astrophysics - High Energy Astrophysical Phenomena

| arxiv:1706.01812 | doi:10.1103/PhysRevLett.118.221101 |

{We describe the observation of GW170104, a gravitational-wave signal produced by the coalescence of a pair of stellar-mass black holes. The signal was measured on January 4, 2017 at 10{\ensuremath{:}}11:58.6 UTC by the twin advanced detectors of the Laser Interferometer Gravitational-Wave Observatory during their second observing run, with a network signal-to-noise ratio of 13 and a false alarm rate less than 1 in 70 000 years. The inferred component black hole masses are 31. 2$_{-6.0}$$^{+8.4}$M$_{☉}$ and 19. 4$_{-5.9}$$^{+5.3}$ M$_{☉}$ (at the 90\% credible level). The black hole spins are best constrained through measurement of the effective inspiral spin parameter, a mass-weighted combination of the spin components perpendicular to the orbital plane, {\ensuremath{\chi}}$_{eff}$=-0.1 2$_{-0.30}$$^{+0.21}$ . This result implies that spin configurations with both component spins positively aligned with the orbital angular momentum are disfavored. The source luminosity distance is 88 0$_{-390}$$^{+450}$ Mpc corresponding to a redshift of z =0.1 8$_{-0.07}$$^{+0.08}$ . We constrain the magnitude of modifications to the gravitational-wave dispersion relation and perform null tests of general relativity. Assuming that gravitons are dispersed in vacuum like massive particles, we bound the graviton mass to m$_{g}${\ensuremath{\leq}}7.7 {\texttimes}10$^{-23}$ eV /c$^{2}$ . In all cases, we find that GW170104 is consistent with general relativity.}
    @article{ 2017PhRvL.118v1101A,
    
    title = { GW170104: Observation of a 50-Solar-Mass Binary Black Hole Coalescence at Redshift 0.2 },
    journal = { Physical Review Letters },
    year = { 2017 },
    month = { June },
    volume = { 118 },
    number = { 22 },
    pages = { 221101 },
    doi = { 10.1103/PhysRevLett.118.221101 },
    }
    

Search for intermediate mass black hole binaries in the first observing run of Advanced LIGO

Physical Review D, 96, 022001

General Relativity and Quantum Cosmology

| arxiv:1704.04628 | doi:10.1103/PhysRevD.96.022001 |

{During their first observational run, the two Advanced LIGO detectors attained an unprecedented sensitivity, resulting in the first direct detections of gravitational-wave signals produced by stellar-mass binary black hole systems. This paper reports on an all-sky search for gravitational waves (GWs) from merging intermediate mass black hole binaries (IMBHBs). The combined results from two independent search techniques were used in this study: the first employs a matched-filter algorithm that uses a bank of filters covering the GW signal parameter space, while the second is a generic search for GW transients (bursts). No GWs from IMBHBs were detected; therefore, we constrain the rate of several classes of IMBHB mergers. The most stringent limit is obtained for black holes of individual mass 100 M$_{☉}$ , with spins aligned with the binary orbital angular momentum. For such systems, the merger rate is constrained to be less than 0.93 Gpc$^{-3}$ yr$^{-1}$ in comoving units at the 90\% confidence level, an improvement of nearly 2 orders of magnitude over previous upper limits.

}

    @article{ 2017PhRvD..96b2001A,
    
    title = { Search for intermediate mass black hole binaries in the first observing run of Advanced LIGO },
    journal = { Physical Review D },
    year = { 2017 },
    month = { July },
    volume = { 96 },
    number = { 2 },
    pages = { 022001 },
    doi = { 10.1103/PhysRevD.96.022001 },
    }
    

Search for high-energy neutrinos from gravitational wave event GW151226 and candidate LVT151012 with ANTARES and IceCube

Physical Review D, 96, 022005

Astrophysics - High Energy Astrophysical Phenomena

| arxiv:1703.06298 | doi:10.1103/PhysRevD.96.022005 |

{The Advanced LIGO observatories detected gravitational waves from two binary black hole mergers during their first observation run (O1). We present a high-energy neutrino follow-up search for the second gravitational wave event, GW151226, as well as for gravitational wave candidate LVT151012. We find two and four neutrino candidates detected by IceCube, and one and zero detected by Antares, within {\ensuremath{\pm}}500 s around the respective gravitational wave signals, consistent with the expected background rate. None of these neutrino candidates are found to be directionally coincident with GW151226 or LVT151012. We use nondetection to constrain isotropic-equivalent high- energy neutrino emission from GW151226, adopting the GW event's 3D localization, to less than 2 {\texttimes}1 {}0$^{51}$- 2 {\texttimes}1 {}0$^{54}$ erg .

}

    @article{ 2017PhRvD..96b2005A,
    
    title = { Search for high-energy neutrinos from gravitational wave event GW151226 and candidate LVT151012 with ANTARES and IceCube },
    journal = { Physical Review D },
    year = { 2017 },
    month = { July },
    volume = { 96 },
    number = { 2 },
    pages = { 022005 },
    doi = { 10.1103/PhysRevD.96.022005 },
    }
    

Upper Limits on Gravitational Waves from Scorpius X-1 from a Model-based Cross-correlation Search in Advanced LIGO Data

Astrophysical Journal, 847, 47

accretion accretion disks gravitational waves stars: neutron X-rays: binaries Astrophysics - High Energy Astrophysical Phenomena General Relativity and Quantum Cosmology

| arxiv:1706.03119 | doi:10.3847/1538-4357/aa86f0 |

{We present the results of a semicoherent search for continuous gravitational waves from the low-mass X-ray binary Scorpius X-1, using data from the first Advanced LIGO observing run. The search method uses details of the modeled, parametrized continuous signal to combine coherently data separated by less than a specified coherence time, which can be adjusted to trade off sensitivity against computational cost. A search was conducted over the frequency range 25-2000 \{Hz\}, spanning the current observationally constrained range of binary orbital parameters. No significant detection candidates were found, and frequency-dependent upper limits were set using a combination of sensitivity estimates and simulated signal injections. The most stringent upper limit was set at 175 \{Hz\}, with comparable limits set across the most sensitive frequency range from 100 to 200 \{Hz\}. At this frequency, the 95\% upper limit on the signal amplitude h $_{0}$ is 2.3{\texttimes} \{10\}$^{-25}$ marginalized over the unknown inclination angle of the neutron star{\textquoteright}s spin, and 8.0{\texttimes} \{10\}$^{-26}$ assuming the best orientation (which results in circularly polarized gravitational waves). These limits are a factor of 3-4 stronger than those set by other analyses of the same data, and a factor of ̃7 stronger than the best upper limits set using data from Initial LIGO science runs. In the vicinity of 100 \{Hz\}, the limits are a factor of between 1.2 and 3.5 above the predictions of the torque balance model, depending on the inclination angle; if the most likely inclination angle of 44{\textdegree} is assumed, they are within a factor of 1.7.}
    @article{ 2017ApJ...847...47A,
    
    title = { Upper Limits on Gravitational Waves from Scorpius X-1 from a Model-based Cross-correlation Search in Advanced LIGO Data },
    journal = { Astrophysical Journal },
    year = { 2017 },
    month = { September },
    volume = { 847 },
    number = { 1 },
    pages = { 47 },
    doi = { 10.3847/1538-4357/aa86f0 },
    }
    

All-sky search for periodic gravitational waves in the O1 LIGO data

Physical Review D, 96, 062002

General Relativity and Quantum Cosmology Astrophysics - Instrumentation and Methods for Astrophysics

| arxiv:1707.02667 | doi:10.1103/PhysRevD.96.062002 |

{We report on an all-sky search for periodic gravitational waves in the frequency band 20-475 Hz and with a frequency time derivative in the range of [-1.0 ,+0.1 ] {\texttimes}10$^{-8}$ Hz /s . Such a signal could be produced by a nearby spinning and slightly nonaxisymmetric isolated neutron star in our galaxy. This search uses the data from Advanced LIGO's first observational run, O1. No periodic gravitational wave signals were observed, and upper limits were placed on their strengths. The lowest upper limits on worst-case (linearly polarized) strain amplitude h$_{0}$ are ̃4 {\texttimes}10$^{-25}$ near 170 Hz. For a circularly polarized source (most favorable orientation), the smallest upper limits obtained are ̃1.5 {\texttimes}10$^{-25}$. These upper limits refer to all sky locations and the entire range of frequency derivative values. For a population-averaged ensemble of sky locations and stellar orientations, the lowest upper limits obtained for the strain amplitude are ̃2.5 {\texttimes}10$^{-25}$.

}

    @article{ 2017PhRvD..96f2002A,
    
    title = { All-sky search for periodic gravitational waves in the O1 LIGO data },
    journal = { Physical Review D },
    year = { 2017 },
    month = { September },
    volume = { 96 },
    number = { 6 },
    pages = { 062002 },
    doi = { 10.1103/PhysRevD.96.062002 },
    }
    

Multi-messenger Observations of a Binary Neutron Star Merger

\apjl, 848, L12

gravitational waves stars: neutron Astrophysics - High Energy Astrophysical Phenomena General Relativity and Quantum Cosmology

| arxiv:1710.05833 | doi:10.3847/2041-8213/aa91c9 |

{On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ̃ 1.7 \{\{s\}\} with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg$^{2}$ at a luminosity distance of \{40\}$_{-8}$$^{+8}$ Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 \{M\}$_{☉ }$. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ̃ 40 \{\{Mpc\}\}) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ̃10 days. Following early non-detections, X-ray and radio emission were discovered at the transient's position ̃ 9 and ̃ 16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC 4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta.

Any correspondence should be addressed to .}

    @article{ 2017ApJ...848L..12A,
    
    title = { Multi-messenger Observations of a Binary Neutron Star Merger },
    journal = { \apjl },
    year = { 2017 },
    month = { October },
    volume = { 848 },
    number = { 2 },
    pages = { L12 },
    doi = { 10.3847/2041-8213/aa91c9 },
    }
    

Gravitational Waves and Gamma-Rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A

\apjl, 848, L13

binaries: close gamma-ray burst: general gravitational waves Astrophysics - High Energy Astrophysical Phenomena General Relativity and Quantum Cosmology

| arxiv:1710.05834 | doi:10.3847/2041-8213/aa920c |

{On 2017 August 17, the gravitational-wave event GW170817 was observed by the Advanced LIGO and Virgo detectors, and the gamma-ray burst (GRB) GRB 170817A was observed independently by the Fermi Gamma- ray Burst Monitor, and the Anti-Coincidence Shield for the Spectrometer for the International Gamma-Ray Astrophysics Laboratory. The probability of the near-simultaneous temporal and spatial observation of GRB 170817A and GW170817 occurring by chance is 5.0{\texttimes} \{10\}$^{-8}$. We therefore confirm binary neutron star mergers as a progenitor of short GRBs. The association of GW170817 and GRB 170817A provides new insight into fundamental physics and the origin of short GRBs. We use the observed time delay of (+1.74+/- 0.05) \{\{s\}\} between GRB 170817A and GW170817 to: (I) constrain the difference between the speed of gravity and the speed of light to be between -3{\texttimes} \{10\}$^{-15}$ and +7{\texttimes} \{10\}$^{-16}$ times the speed of light, (II) place new bounds on the violation of Lorentz invariance, (III) present a new test of the equivalence principle by constraining the Shapiro delay between gravitational and electromagnetic radiation. We also use the time delay to constrain the size and bulk Lorentz factor of the region emitting the gamma-rays. GRB 170817A is the closest short GRB with a known distance, but is between 2 and 6 orders of magnitude less energetic than other bursts with measured redshift. A new generation of gamma-ray detectors, and subthreshold searches in existing detectors, will be essential to detect similar short bursts at greater distances. Finally, we predict a joint detection rate for the Fermi Gamma-ray Burst Monitor and the Advanced LIGO and Virgo detectors of 0.1-1.4 per year during the 2018-2019 observing run and 0.3-1.7 per year at design sensitivity.}
    @article{ 2017ApJ...848L..13A,
    
    title = { Gravitational Waves and Gamma-Rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A },
    journal = { \apjl },
    year = { 2017 },
    month = { October },
    volume = { 848 },
    number = { 2 },
    pages = { L13 },
    doi = { 10.3847/2041-8213/aa920c },
    }
    

GW170814: A Three-Detector Observation of Gravitational Waves from a Binary Black Hole Coalescence

Physical Review Letters, 119, 141101

General Relativity and Quantum Cosmology Astrophysics - High Energy Astrophysical Phenomena

| arxiv:1709.09660 | doi:10.1103/PhysRevLett.119.141101 |

{On August 14, 2017 at 10{\ensuremath{:}}30:43 UTC, the Advanced Virgo detector and the two Advanced LIGO detectors coherently observed a transient gravitational-wave signal produced by the coalescence of two stellar mass black holes, with a false-alarm rate of {\ensuremath{\lesssim}}1 in 27 000 years. The signal was observed with a three-detector network matched-filter signal-to- noise ratio of 18. The inferred masses of the initial black holes are 30. 5$_{-3.0}$$^{+5.7}$M$_{☉}$ and 25 .3$_{-4.2}$$^{+2.8}$M$_{☉}$ (at the 90\% credible level). The luminosity distance of the source is 54 0$_{-210}$$^{+130}$ Mpc , corresponding to a redshift of z =0.1 1$_{-0.04}$$^{+0.03}$. A network of three detectors improves the sky localization of the source, reducing the area of the 90\% credible region from 1160 deg$^{2}$ using only the two LIGO detectors to 60 deg$^{2}$ using all three detectors. For the first time, we can test the nature of gravitational-wave polarizations from the antenna response of the LIGO-Virgo network, thus enabling a new class of phenomenological tests of gravity.

}

    @article{ 2017PhRvL.119n1101A,
    
    title = { GW170814: A Three-Detector Observation of Gravitational Waves from a Binary Black Hole Coalescence },
    journal = { Physical Review Letters },
    year = { 2017 },
    month = { October },
    volume = { 119 },
    number = { 14 },
    pages = { 141101 },
    doi = { 10.1103/PhysRevLett.119.141101 },
    }
    

GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral

Physical Review Letters, 119, 161101

General Relativity and Quantum Cosmology Astrophysics - High Energy Astrophysical Phenomena

| arxiv:1710.05832 | doi:10.1103/PhysRevLett.119.161101 |

{On August 17, 2017 at 12{\ensuremath{:}}41:04 UTC the Advanced LIGO and Advanced Virgo gravitational-wave detectors made their first observation of a binary neutron star inspiral. The signal, GW170817, was detected with a combined signal-to-noise ratio of 32.4 and a false-alarm-rate estimate of less than one per 8.0 {\texttimes}{}10$^{4}$ years . We infer the component masses of the binary to be between 0.86 and 2.26 M$_{☉}$ , in agreement with masses of known neutron stars. Restricting the component spins to the range inferred in binary neutron stars, we find the component masses to be in the range 1.17 - 1.60 M$_{☉}$ , with the total mass of the system 2.7 4$_{-0.01}$$^{+0.04}$M$_{☉}$ . The source was localized within a sky region of 28 deg$^{2}$ (90\% probability) and had a luminosity distance of 4 0$_{-14}$$^{+8}$ Mpc , the closest and most precisely localized gravitational-wave signal yet. The association with the {\ensuremath{\gamma}} -ray burst GRB 170817A, detected by Fermi- GBM 1.7 s after the coalescence, corroborates the hypothesis of a neutron star merger and provides the first direct evidence of a link between these mergers and short {\ensuremath{\gamma}} -ray bursts. Subsequent identification of transient counterparts across the electromagnetic spectrum in the same location further supports the interpretation of this event as a neutron star merger. This unprecedented joint gravitational and electromagnetic observation provides insight into astrophysics, dense matter, gravitation, and cosmology.

}

    @article{ 2017PhRvL.119p1101A,
    
    title = { GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral },
    journal = { Physical Review Letters },
    year = { 2017 },
    month = { October },
    volume = { 119 },
    number = { 16 },
    pages = { 161101 },
    doi = { 10.1103/PhysRevLett.119.161101 },
    }
    

A gravitational-wave standard siren measurement of the Hubble constant

\nat, 551, 85-88

Astrophysics - Cosmology and Nongalactic Astrophysics

| arxiv:1710.05835 | doi:10.1038/nature24471 |

{On 17 August 2017, the Advanced LIGO and Virgo detectors observed the gravitational-wave event GW170817{\textemdash}a strong signal from the merger of a binary neutron-star system. Less than two seconds after the merger, a {\ensuremath{\gamma}}-ray burst (GRB 170817A) was detected within a region of the sky consistent with the LIGO-Virgo-derived location of the gravitational-wave source. This sky region was subsequently observed by optical astronomy facilities, resulting in the identification of an optical transient signal within about ten arcseconds of the galaxy NGC 4993. This detection of GW170817 in both gravitational waves and electromagnetic waves represents the first {\textquoteleft}multi-messenger{\textquoteright} astronomical observation. Such observations enable GW170817 to be used as a {\textquoteleft}standard siren{\textquoteright} (meaning that the absolute distance to the source can be determined directly from the gravitational-wave measurements) to measure the Hubble constant. This quantity represents the local expansion rate of the Universe, sets the overall scale of the Universe and is of fundamental importance to cosmology. Here we report a measurement of the Hubble constant that combines the distance to the source inferred purely from the gravitational- wave signal with the recession velocity inferred from measurements of the redshift using the electromagnetic data. In contrast to previous measurements, ours does not require the use of a cosmic {\textquoteleft}distance ladder{\textquoteright}: the gravitational-wave analysis can be used to estimate the luminosity distance out to cosmological scales directly, without the use of intermediate astronomical distance measurements. We determine the Hubble constant to be about 70 kilometres per second per megaparsec. This value is consistent with existing measurements, while being completely independent of them. Additional standard siren measurements from future gravitational-wave sources will enable the Hubble constant to be constrained to high precision.}
    @article{ 2017Natur.551...85A,
    
    title = { A gravitational-wave standard siren measurement of the Hubble constant },
    journal = { \nat },
    year = { 2017 },
    month = { November },
    volume = { 551 },
    number = { 7678 },
    pages = { 85-88 },
    doi = { 10.1038/nature24471 },
    }
    

VizieR Online Data Catalog: Gravitational waves search from known PSR with LIGO (Abbott+, 2017)

VizieR Online Data Catalog, J/ApJ/839/12

Pulsars Stars: distances

|

{We have obtained timings for 200 known pulsars. Timing was performed using the 42ft telescope and Lovell telescope at Jodrell Bank (UK), the 26m telescope at Hartebeesthoek (South Africa), the Parkes radio telescope (Australia), the Nancay Decimetric Radio Telescope (France), the Arecibo Observatory (Puerto Rico) and the Fermi Large Area Telescope (LAT). Of these, 122 have been targeted in previous campaigns (Aasi+ 2014, J/ApJ/785/119), while 78 are new to this search.

(1 data file).}

    @article{ 2017yCat..18390012A,
    
    title = { VizieR Online Data Catalog: Gravitational waves search from known PSR with LIGO (Abbott+, 2017) },
    journal = { VizieR Online Data Catalog },
    year = { 2017 },
    month = { November },
    pages = { J/ApJ/839/12 },
    }
    

Search for High-energy Neutrinos from Binary Neutron Star Merger GW170817 with ANTARES, IceCube, and the Pierre Auger Observatory

\apjl, 850, L35

gamma-ray burst: general gravitational waves neutrinos Astrophysics - High Energy Astrophysical Phenomena

| arxiv:1710.05839 | doi:10.3847/2041-8213/aa9aed |

{The Advanced LIGO and Advanced Virgo observatories recently discovered gravitational waves from a binary neutron star inspiral. A short gamma-ray burst (GRB) that followed the merger of this binary was also recorded by the Fermi Gamma-ray Burst Monitor (Fermi- GBM), and the Anti-Coincidence Shield for the Spectrometer for the International Gamma-Ray Astrophysics Laboratory (INTEGRAL), indicating particle acceleration by the source. The precise location of the event was determined by optical detections of emission following the merger. We searched for high-energy neutrinos from the merger in the GeV-EeV energy range using the ANTARES, IceCube, and Pierre Auger Observatories. No neutrinos directionally coincident with the source were detected within {\ensuremath{\pm}}500 s around the merger time. Additionally, no MeV neutrino burst signal was detected coincident with the merger. We further carried out an extended search in the direction of the source for high-energy neutrinos within the 14 day period following the merger, but found no evidence of emission. We used these results to probe dissipation mechanisms in relativistic outflows driven by the binary neutron star merger. The non-detection is consistent with model predictions of short GRBs observed at a large off-axis angle.}
    @article{ 2017ApJ...850L..35A,
    
    title = { Search for High-energy Neutrinos from Binary Neutron Star Merger GW170817 with ANTARES, IceCube, and the Pierre Auger Observatory },
    journal = { \apjl },
    year = { 2017 },
    month = { December },
    volume = { 850 },
    number = { 2 },
    pages = { L35 },
    doi = { 10.3847/2041-8213/aa9aed },
    }
    

Estimating the Contribution of Dynamical Ejecta in the Kilonova Associated with GW170817

\apjl, 850, L39

gravitational waves methods: data analysis stars: neutron Astrophysics - High Energy Astrophysical Phenomena

| arxiv:1710.05836 | doi:10.3847/2041-8213/aa9478 |

{The source of the gravitational-wave (GW) signal GW170817, very likely a binary neutron star merger, was also observed electromagnetically, providing the first multi-messenger observations of this type. The two-week-long electromagnetic (EM) counterpart had a signature indicative of an r-process- induced optical transient known as a kilonova. This Letter examines how the mass of the dynamical ejecta can be estimated without a direct electromagnetic observation of the kilonova, using GW measurements and a phenomenological model calibrated to numerical simulations of mergers with dynamical ejecta. Specifically, we apply the model to the binary masses inferred from the GW measurements, and use the resulting mass of the dynamical ejecta to estimate its contribution (without the effects of wind ejecta) to the corresponding kilonova light curves from various models. The distributions of dynamical ejecta mass range between \{M\}$_{\{ej}$\}=\{10\}$^{-3}$-\{10\}$^{-2}$ \{M\}$_{☉ }$ for various equations of state, assuming that the neutron stars are rotating slowly. In addition, we use our estimates of the dynamical ejecta mass and the neutron star merger rates inferred from GW170817 to constrain the contribution of events like this to the r-process element abundance in the Galaxy when ejecta mass from post-merger winds is neglected. We find that if {\ensuremath{\gtrsim}}10\% of the matter dynamically ejected from binary neutron star (BNS) mergers is converted to r-process elements, GW170817-like BNS mergers could fully account for the amount of r-process material observed in the Milky Way.}
    @article{ 2017ApJ...850L..39A,
    
    title = { Estimating the Contribution of Dynamical Ejecta in the Kilonova Associated with GW170817 },
    journal = { \apjl },
    year = { 2017 },
    month = { December },
    volume = { 850 },
    number = { 2 },
    pages = { L39 },
    doi = { 10.3847/2041-8213/aa9478 },
    }
    

On the Progenitor of Binary Neutron Star Merger GW170817

\apjl, 850, L40

binaries: general gravitational waves stars: kinematics and dynamics stars: neutron Astrophysics - High Energy Astrophysical Phenomena

| arxiv:1710.05838 | doi:10.3847/2041-8213/aa93fc |

{On 2017 August 17 the merger of two compact objects with masses consistent with two neutron stars was discovered through gravitational-wave (GW170817), gamma-ray (GRB 170817A), and optical (SSS17a/AT 2017gfo) observations. The optical source was associated with the early-type galaxy NGC 4993 at a distance of just ̃40 Mpc, consistent with the gravitational-wave measurement, and the merger was localized to be at a projected distance of ̃2 kpc away from the galaxy{\textquoteright}s center. We use this minimal set of facts and the mass posteriors of the two neutron stars to derive the first constraints on the progenitor of GW170817 at the time of the second supernova (SN). We generate simulated progenitor populations and follow the three-dimensional kinematic evolution from binary neutron star (BNS) birth to the merger time, accounting for pre-SN galactic motion, for considerably different input distributions of the progenitor mass, pre-SN semimajor axis, and SN-kick velocity. Though not considerably tight, we find these constraints to be comparable to those for Galactic BNS progenitors. The derived constraints are very strongly influenced by the requirement of keeping the binary bound after the second SN and having the merger occur relatively close to the center of the galaxy. These constraints are insensitive to the galaxy{\textquoteright}s star formation history, provided the stellar populations are older than 1 Gyr.}
    @article{ 2017ApJ...850L..40A,
    
    title = { On the Progenitor of Binary Neutron Star Merger GW170817 },
    journal = { \apjl },
    year = { 2017 },
    month = { December },
    volume = { 850 },
    number = { 2 },
    pages = { L40 },
    doi = { 10.3847/2041-8213/aa93fc },
    }
    

Erratum: {\textquotedblleft}First Search for Gravitational Waves from Known Pulsars with Advanced LIGO{\textquotedblright} (2017, ApJ, 839, 12)

Astrophysical Journal, 851, 71

| doi:10.3847/1538-4357/aa9aee |

    @article{ 2017ApJ...851...71A,
    
    title = { Erratum: {\textquotedblleft}First Search for Gravitational Waves from Known Pulsars with Advanced LIGO{\textquotedblright} (2017, ApJ, 839, 12) },
    journal = { Astrophysical Journal },
    year = { 2017 },
    month = { December },
    volume = { 851 },
    number = { 1 },
    pages = { 71 },
    doi = { 10.3847/1538-4357/aa9aee },
    }
    

Search for Post-merger Gravitational Waves from the Remnant of the Binary Neutron Star Merger GW170817

\apjl, 851, L16

gravitational waves methods: data analysis stars: neutron Astrophysics - High Energy Astrophysical Phenomena General Relativity and Quantum Cosmology

| arxiv:1710.09320 | doi:10.3847/2041-8213/aa9a35 |

{The first observation of a binary neutron star (NS) coalescence by the Advanced LIGO and Advanced Virgo gravitational-wave (GW) detectors offers an unprecedented opportunity to study matter under the most extreme conditions. After such a merger, a compact remnant is left over whose nature depends primarily on the masses of the inspiraling objects and on the equation of state of nuclear matter. This could be either a black hole (BH) or an NS, with the latter being either long-lived or too massive for stability implying delayed collapse to a BH. Here, we present a search for GWs from the remnant of the binary NS merger GW170817 using data from Advanced LIGO and Advanced Virgo. We search for short- ({\ensuremath{\lesssim}}1 s) and intermediate-duration ({\ensuremath{\lesssim}}500 s) signals, which include GW emission from a hypermassive NS or supramassive NS, respectively. We find no signal from the post-merger remnant. Our derived strain upper limits are more than an order of magnitude larger than those predicted by most models. For short signals, our best upper limit on the root sum square of the GW strain emitted from 1-4 kHz is \{h\}$_{\{rss}$\}$^{50 \% }$=2.1{\texttimes} \{10\}$^{-22}$ \{\{Hz\}\}$^{-1/2}$ at 50\% detection efficiency. For intermediate-duration signals, our best upper limit at 50\% detection efficiency is \{h\}$_{\{rss}$\}$^{50 \% }$=8.4{\texttimes} \{10\}$^{-22}$ \{\{Hz\}\}$^{-1/2}$ for a millisecond magnetar model, and \{h\}$_{\{rss}$\}$^{50 \% }$=5.9{\texttimes} \{10\}$^{-22}$ \{\{Hz\}\}$^{-1/2}$ for a bar-mode model. These results indicate that post-merger emission from a similar event may be detectable when advanced detectors reach design sensitivity or with next- generation detectors.}
    @article{ 2017ApJ...851L..16A,
    
    title = { Search for Post-merger Gravitational Waves from the Remnant of the Binary Neutron Star Merger GW170817 },
    journal = { \apjl },
    year = { 2017 },
    month = { December },
    volume = { 851 },
    number = { 1 },
    pages = { L16 },
    doi = { 10.3847/2041-8213/aa9a35 },
    }
    

GW170608: Observation of a 19 Solar-mass Binary Black Hole Coalescence

\apjl, 851, L35

binaries: general gravitational waves stars: black holes Astrophysics - High Energy Astrophysical Phenomena General Relativity and Quantum Cosmology

| arxiv:1711.05578 | doi:10.3847/2041-8213/aa9f0c |

{On 2017 June 8 at 02:01:16.49 UTC, a gravitational-wave (GW) signal from the merger of two stellar-mass black holes was observed by the two Advanced Laser Interferometer Gravitational-Wave Observatory detectors with a network signal-to-noise ratio of 13. This system is the lightest black hole binary so far observed, with component masses of \{12\}$_{-2}$$^{+7}$ \{M\}$_{☉ }$ and \{7\}$_{-2}$$^{+2}$ \{M\}$_{☉ }$ (90\% credible intervals). These lie in the range of measured black hole masses in low-mass X-ray binaries, thus allowing us to compare black holes detected through GWs with electromagnetic observations. The source{\textquoteright}s luminosity distance is \{340\}$_{-140}$$^{+140}$ \{Mpc\}, corresponding to redshift \{0.07\}$_{-0.03}$$^{+0.03}$. We verify that the signal waveform is consistent with the predictions of general relativity.}
    @article{ 2017ApJ...851L..35A,
    
    title = { GW170608: Observation of a 19 Solar-mass Binary Black Hole Coalescence },
    journal = { \apjl },
    year = { 2017 },
    month = { December },
    volume = { 851 },
    number = { 2 },
    pages = { L35 },
    doi = { 10.3847/2041-8213/aa9f0c },
    }
    

First low-frequency Einstein@Home all-sky search for continuous gravitational waves in Advanced LIGO data

Physical Review D, 96, 122004

General Relativity and Quantum Cosmology

| arxiv:1707.02669 | doi:10.1103/PhysRevD.96.122004 |

{We report results of a deep all-sky search for periodic gravitational waves from isolated neutron stars in data from the first Advanced LIGO observing run. This search investigates the low frequency range of Advanced LIGO data, between 20 and 100 Hz, much of which was not explored in initial LIGO. The search was made possible by the computing power provided by the volunteers of the Einstein@Home project. We find no significant signal candidate and set the most stringent upper limits to date on the amplitude of gravitational wave signals from the target population, corresponding to a sensitivity depth of 48.7 [1 /{\ensuremath{\sqrt{}}}\{Hz \}] . At the frequency of best strain sensitivity, near 100 Hz, we set 90\% confidence upper limits of 1.8 {\texttimes}1 0$^{-25}$. At the low end of our frequency range, 20 Hz, we achieve upper limits of 3.9 {\texttimes}1 0$^{-24}$. At 55 Hz we can exclude sources with ellipticities greater than 1 0$^{-5}$ within 100 pc of Earth with fiducial value of the principal moment of inertia of {}10$^{38}$ kg m$^{2}$ .

}

    @article{ 2017PhRvD..96l2004A,
    
    title = { First low-frequency Einstein@Home all-sky search for continuous gravitational waves in Advanced LIGO data },
    journal = { Physical Review D },
    year = { 2017 },
    month = { December },
    volume = { 96 },
    number = { 12 },
    pages = { 122004 },
    doi = { 10.1103/PhysRevD.96.122004 },
    }
    

First narrow-band search for continuous gravitational waves from known pulsars in advanced detector data

Physical Review D, 96, 122006

General Relativity and Quantum Cosmology Astrophysics - High Energy Astrophysical Phenomena

| arxiv:1710.02327 | doi:10.1103/PhysRevD.96.122006 |

{Spinning neutron stars asymmetric with respect to their rotation axis are potential sources of continuous gravitational waves for ground-based interferometric detectors. In the case of known pulsars a fully coherent search, based on matched filtering, which uses the position and rotational parameters obtained from electromagnetic observations, can be carried out. Matched filtering maximizes the signal-to-noise (SNR) ratio, but a large sensitivity loss is expected in case of even a very small mismatch between the assumed and the true signal parameters. For this reason, narrow-band analysis methods have been developed, allowing a fully coherent search for gravitational waves from known pulsars over a fraction of a hertz and several spin-down values. In this paper we describe a narrow-band search of 11 pulsars using data from Advanced LIGO's first observing run. Although we have found several initial outliers, further studies show no significant evidence for the presence of a gravitational wave signal. Finally, we have placed upper limits on the signal strain amplitude lower than the spin-down limit for 5 of the 11 targets over the bands searched; in the case of J1813-1749 the spin-down limit has been beaten for the first time. For an additional 3 targets, the median upper limit across the search bands is below the spin-down limit. This is the most sensitive narrow-band search for continuous gravitational waves carried out so far.

}

    @article{ 2017PhRvD..96l2006A,
    
    title = { First narrow-band search for continuous gravitational waves from known pulsars in advanced detector data },
    journal = { Physical Review D },
    year = { 2017 },
    month = { December },
    volume = { 96 },
    number = { 12 },
    pages = { 122006 },
    doi = { 10.1103/PhysRevD.96.122006 },
    }
    

Observing gravitational-wave transient GW150914 with minimal assumptions

Physical Review D, 93, 122004

General Relativity and Quantum Cosmology Astrophysics - High Energy Astrophysical Phenomena Astrophysics - Instrumentation and Methods for Astrophysics

| arxiv:1602.03843 | doi:10.1103/PhysRevD.93.122004 |

{The gravitational-wave signal GW150914 was first identified on September 14, 2015, by searches for short-duration gravitational-wave transients. These searches identify time-correlated transients in multiple detectors with minimal assumptions about the signal morphology, allowing them to be sensitive to gravitational waves emitted by a wide range of sources including binary black hole mergers. Over the observational period from September 12 to October 20, 2015, these transient searches were sensitive to binary black hole mergers similar to GW150914 to an average distance of ̃600 Mpc . In this paper, we describe the analyses that first detected GW150914 as well as the parameter estimation and waveform reconstruction techniques that initially identified GW150914 as the merger of two black holes. We find that the reconstructed waveform is consistent with the signal from a binary black hole merger with a chirp mass of ̃30 M$_{☉}$ and a total mass before merger of ̃70 M$_{☉}$ in the detector frame.

}

    @article{ 2016PhRvD..93l2004A,
    
    title = { Observing gravitational-wave transient GW150914 with minimal assumptions },
    journal = { Physical Review D },
    year = { 2016 },
    month = { June },
    volume = { 93 },
    number = { 12 },
    pages = { 122004 },
    doi = { 10.1103/PhysRevD.93.122004 },
    }
    

Tests of General Relativity with GW150914

Physical Review Letters, 116, 221101

General Relativity and Quantum Cosmology

| arxiv:1602.03841 | doi:10.1103/PhysRevLett.116.221101 |

{The LIGO detection of GW150914 provides an unprecedented opportunity to study the two-body motion of a compact-object binary in the large-velocity, highly nonlinear regime, and to witness the final merger of the binary and the excitation of uniquely relativistic modes of the gravitational field. We carry out several investigations to determine whether GW150914 is consistent with a binary black-hole merger in general relativity. We find that the final remnant's mass and spin, as determined from the low-frequency (inspiral) and high-frequency (postinspiral) phases of the signal, are mutually consistent with the binary black-hole solution in general relativity. Furthermore, the data following the peak of GW150914 are consistent with the least-damped quasinormal mode inferred from the mass and spin of the remnant black hole. By using waveform models that allow for parametrized general-relativity violations during the inspiral and merger phases, we perform quantitative tests on the gravitational-wave phase in the dynamical regime and we determine the first empirical bounds on several high- order post-Newtonian coefficients. We constrain the graviton Compton wavelength, assuming that gravitons are dispersed in vacuum in the same way as particles with mass, obtaining a 90\%-confidence lower bound of {}10$^{13}$ km . In conclusion, within our statistical uncertainties, we find no evidence for violations of general relativity in the genuinely strong-field regime of gravity.

}

    @article{ 2016PhRvL.116v1101A,
    
    title = { Tests of General Relativity with GW150914 },
    journal = { Physical Review Letters },
    year = { 2016 },
    month = { June },
    volume = { 116 },
    number = { 22 },
    pages = { 221101 },
    doi = { 10.1103/PhysRevLett.116.221101 },
    }
    

VizieR Online Data Catalog: Bayesian method for detecting stellar flares (Pitkin+, 2014)

M. Pitkin, D. Williams, L. Fletcher, S.~D.~T. Grant

VizieR Online Data Catalog, J/MNRAS/445/2268

Stars: flare Effective temperatures

|

{We present a Bayesian-odds-ratio-based algorithm for detecting stellar flares in light-curve data. We assume flares are described by a model in which there is a rapid rise with a half-Gaussian profile, followed by an exponential decay. Our signal model also contains a polynomial background model required to fit underlying light-curve variations in the data, which could otherwise partially mimic a flare. We characterize the false alarm probability and efficiency of this method under the assumption that any unmodelled noise in the data is Gaussian, and compare it with a simpler thresholding method based on that used in Walkowicz et al. We find our method has a significant increase in detection efficiency for low signal-to-noise ratio (S/N) flares. For a conservative false alarm probability our method can detect 95 per cent of flares with S/N less than 20, as compared to S/N of 25 for the simpler method. We also test how well the assumption of Gaussian noise holds by applying the method to a selection of 'quiet' Kepler stars. As an example we have applied our method to a selection of stars in Kepler Quarter 1 data. The method finds 687 flaring stars with a total of 1873 flares after vetos have been applied. For these flares we have made preliminary characterizations of their durations and and S/N.

(1 data file).

}

    @article{ 2015yCat..74452268P,
    author = { Pitkin, M } and { Williams, D } and { Fletcher, L } and { Grant, S },
    title = { VizieR Online Data Catalog: Bayesian method for detecting stellar flares (Pitkin+, 2014) },
    journal = { VizieR Online Data Catalog },
    year = { 2015 },
    month = { May },
    pages = { J/MNRAS/445/2268 },
    }
    

BayesFlare: Bayesian method for detecting stellar flares

M. Pitkin, D. Williams, L. Fletcher, S.~D.~T. Grant

, ascl:1407.015

Software

| arxiv:1407.015 |

    @article{ 2014ascl.soft07015P,
    author = { Pitkin, M } and { Williams, D } and { Fletcher, L } and { Grant, S },
    title = { BayesFlare: Bayesian method for detecting stellar flares },
    year = { 2014 },
    month = { July },
    pages = { ascl:1407.015 },
    }
    

A Bayesian method for detecting stellar flares

M. Pitkin, D. Williams, L. Fletcher, S.~D.~T. Grant

\mnras, 445, 2268-2284

methods: data analysis methods: statistical stars: flare Astrophysics - Solar and Stellar Astrophysics

| arxiv:1406.1712 | doi:10.1093/mnras/stu1889 |

{We present a Bayesian-odds-ratio-based algorithm for detecting stellar flares in light-curve data. We assume flares are described by a model in which there is a rapid rise with a half-Gaussian profile, followed by an exponential decay. Our signal model also contains a polynomial background model required to fit underlying light-curve variations in the data, which could otherwise partially mimic a flare. We characterize the false alarm probability and efficiency of this method under the assumption that any unmodelled noise in the data is Gaussian, and compare it with a simpler thresholding method based on that used in Walkowicz et al. We find our method has a significant increase in detection efficiency for low signal-to-noise ratio (S/N) flares. For a conservative false alarm probability our method can detect 95 per cent of flares with S/N less than 20, as compared to S/N of 25 for the simpler method. We also test how well the assumption of Gaussian noise holds by applying the method to a selection of `quiet' Kepler stars. As an example we have applied our method to a selection of stars in Kepler Quarter 1 data. The method finds 687 flaring stars with a total of 1873 flares after vetos have been applied. For these flares we have made preliminary characterizations of their durations and and S/N.}
    @article{ 2014MNRAS.445.2268P,
    author = { Pitkin, M } and { Williams, D } and { Fletcher, L } and { Grant, S },
    title = { A Bayesian method for detecting stellar flares },
    journal = { \mnras },
    year = { 2014 },
    month = { December },
    volume = { 445 },
    number = { 3 },
    pages = { 2268-2284 },
    doi = { 10.1093/mnras/stu1889 },
    }
    

A Bayesian method for detecting stellar flares

Matthew Pitkin, Daniel Williams, Lyndsay Fletcher, Samuel Grant

Monthly Notices of the Royal Astronomical Society, 445, 3, 2268-2284

methods: data analysis methods: statistical stars: flare

| arxiv:1406.1712 | doi:10.1093/mnras/stu1889 | ascl:1407.015 |

We present a Bayesian-odds-ratio-based algorithm for detecting stellar flares in light curve data. We assume flares are described by a model in which there is a rapid rise with a half-Gaussian profile, followed by an exponential decay. Our signal model also contains a polynomial background model. This is required to fit underlying light curve variations that are expected in the data, which could otherwise partially mimic a flare. We characterise the false alarm probability and efficiency of this method and compare it with a simpler thresholding method based on that used in Walkowicz et al (2011). We find our method has a significant increase in detection efficiency for low signal-to-noise ratio (S/N) flares. For a conservative false alarm probability our method can detect 95% of flares with S/N less than ~20, as compared to S/N of ~25 for the simpler method. As an example we have applied our method to a selection of stars in Kepler Quarter 1 data. The method finds 687 flaring stars with a total of 1873 flares after vetos have been applied. For these flares we have characterised their durations and and signal-to-noise ratios.
    @article{ 2014MNRAS.445.2268P,
    author =  Matthew Pitkin and   Daniel Williams and   Lyndsay Fletcher and   Samuel Grant,
    title = { A Bayesian method for detecting stellar flares },
    journal = { Monthly Notices of the Royal Astronomical Society },
    year = { 2014 },
    volume = { 445 },
    pages = { 2268-2284 },
    doi = { 10.1093/mnras/stu1889 },
    }