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1. Waveform uncertainty quantification and interpretation for gravitational-wave astronomy

   https://doi.org/10.1088/1361-6382/acd29b  

   Read, Jocelyn ( May 2023 , Classical and Quantum Gravity)

   We demonstrate how to quantify the frequency-domain amplitude and phase accuracy of waveform models,$\delta A$andδφ, in a form that could be marginalized over in gravitational-wave inference using techniques currently applied for quantifying calibration uncertainty. For concreteness, waveform uncertainties affecting neutron-star inspiral measurements are considered, and post-hoc error estimates from a variety of waveform models are made by comparing time-domain and frequency-domain analytic models with multiple-resolution numerical simulations. These waveform uncertainty estimates can be compared to GW170817 calibration envelopes or to Advanced LIGO and Virgo calibration goals. Signal-specific calibration and waveform uncertainties are compared to statistical fluctuations in gravitational-wave observatories, giving frequency-dependent modeling requirements for detectors such as Advanced LIGO Plus, Cosmic Explorer, or Einstein Telescope. Finally, the distribution of waveform error for the GW170817 posterior is computed from tidal models and compared to the constraints onδφor$\delta A$from GWTC-1 by Edelmanet al.In general,δφand$\delta A$can also be interpreted in terms of unmodeled astrophysical energy transfer within or from the source system.

    

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2. Inferring the Neutron Star Maximum Mass and Lower Mass Gap in Neutron Star–Black Hole Systems with Spin

   https://doi.org/10.3847/1538-4357/ac7f99  

   Ye, Christine ; Fishbach, Maya ( September 2022 , The Astrophysical Journal)

   Gravitational-wave (GW) detections of merging neutron star–black hole (NSBH) systems probe astrophysical neutron star (NS) and black hole (BH) mass distributions, especially at the transition between NS and BH masses. Of particular interest are the maximum NS mass, minimum BH mass, and potential mass gap between them. While previous GW population analyses assumed all NSs obey the same maximum mass, if rapidly spinning NSs exist, they can extend to larger maximum masses than nonspinning NSs. In fact, several authors have proposed that the ∼2.6M_⊙object in the event GW190814—either the most massive NS or least massive BH observed to date—is a rapidly spinning NS. We therefore infer the NSBH mass distribution jointly with the NS spin distribution, modeling the NS maximum mass as a function of spin. Using four LIGO–Virgo NSBH events including GW190814, if we assume that the NS spin distribution is uniformly distributed up to the maximum (breakup) spin, we infer the maximum nonspinning NS mass is${2.7}_{-0.4}^{+0.5}{M}_{\odot }$(90% credibility), while assuming only nonspinning NSs, the NS maximum mass must be >2.53M_⊙(90% credibility). The data support the mass gap’s existence, with a minimum BH mass at${5.4}_{-1.0}^{+0.7}{M}_{\odot }$. With future observations, under simplified assumptions, 150 NSBH events may constrain the maximum nonspinning NS mass to ±0.02M_⊙, and we may even measure the relation between the NS spin and maximum mass entirely from GW data. If rapidly rotating NSs exist, their spins and masses must be modeled simultaneously to avoid biasing the NS maximum mass.

    

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3. Bridging the Gap: Categorizing Gravitational-wave Events at the Transition between Neutron Stars and Black Holes

   https://doi.org/10.3847/1538-4357/ac5f03  

   Farah, Amanda ; Fishbach, Maya ; Essick, Reed ; Holz, Daniel E. ; Galaudage, Shanika ( May 2022 , The Astrophysical Journal)

   We search for features in the mass distribution of detected compact binary coalescences which signify the transition between neutron stars (NSs) and black holes (BHs). We analyze all gravitational-wave (GW) detections by the LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration (LVK) made through the end of the first half of the third observing run, and find clear evidence for two different populations of compact objects based solely on GW data. We confidently (99.3%) find a steepening relative to a single power law describing NSs and low-mass BHs below${2.4}_{-0.5}^{+0.5}{M}_{\odot }$, which is consistent with many predictions for the maximum NS mass. We find suggestions of the purported lower mass gap between the most massive NSs and the least massive BHs, but are unable to conclusively resolve it with current data. If it exists, we find the lower mass gap’s edges to lie at${2.2}_{-0.5}^{+0.7}{M}_{\odot }$and${6.0}_{-1.4}^{+2.4}{M}_{\odot }$. We reexamine events that have been deemed “exceptional” by the LVK collaborations in the context of these features. We analyze GW190814 self-consistently in the context of the full population of compact binaries, finding support for its secondary to be either a NS or a lower mass gap object, consistent with previous claims. Our models are the first to accommodate this event, which is an outlier with respect to the binary BH population. We find that GW200105 and GW200115 probe the edges of, and may have components within, the lower mass gap. As future data improve global population models, the classification of these events will also improve.

    

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4. Noise in the LIGO livingston gravitational wave observatory due to trains

   https://doi.org/10.1088/1361-6382/acf01f  

   Glanzer, J. ; Soni, S. ; Spoon, J. ; Effler, A. ; González, G. ( September 2023 , Classical and Quantum Gravity)

   Environmental seismic disturbances limit the sensitivity of LIGO gravitational wave detectors. Trains near the LIGO Livingston detector produce low frequency (0.5–$10\mathrm{H}\mathrm{z}$) ground noise that couples into the gravitational wave sensitive frequency band (10–$100\mathrm{H}\mathrm{z}$) through light reflected in mirrors and other surfaces. We investigate the effect of trains during the Advanced LIGO third observing run, and propose a method to search for narrow band seismic frequencies responsible for contributing to increases in scattered light. Through the use of the linear regression tool Lasso (least absolute shrinkage and selection operator) and glitch correlations, we identify the most common seismic frequencies that correlate with increases in detector noise as 0.6–$0.8\mathrm{H}\mathrm{z}$, 1.7–$1.9\mathrm{H}\mathrm{z}$, 1.8–$2.0\mathrm{H}\mathrm{z}$, and 2.3–$2.5\mathrm{H}\mathrm{z}$in the LIGO Livingston corner station.

    

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5. ArchEnemy: removing scattered-light glitches from gravitational wave data

   https://doi.org/10.1088/1361-6382/ace22f  

   Tolley, Arthur E. ; Cabourn Davies, Gareth S. ; Harry, Ian W. ; Lundgren, Andrew P. ( July 2023 , Classical and Quantum Gravity)

   Data recorded by gravitational wave detectors includes many non-astrophysical transient noise bursts, the most common of which is caused by scattered-light within the detectors. These so-called ‘glitches’ in the data impact the ability to both observe and characterize incoming gravitational wave signals. In this work we use a scattered-light glitch waveform model to identify and characterize scattered-light glitches in a representative stretch of gravitational wave data. We identify 2749 scattered-light glitches in 5.96 days of LIGO-Hanford data and 1306 glitches in 5.93 days of LIGO-Livingston data taken from the third LIGO-Virgo observing run. By subtracting identified scattered-light glitches we demonstrate an increase in the sensitive volume of a gravitational wave search for binary black hole signals by$\sim 1\mathrm{\%}$.

    

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