Bulletin of the American Physical Society
APS April Meeting 2019
Volume 64, Number 3
Saturday–Tuesday, April 13–16, 2019; Denver, Colorado
Session B17: What we are Learning from the Population of Detected Binary Black Hole Mergers |
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Sponsoring Units: DAP DGRAV Room: Sheraton Grand Ballroom II |
Saturday, April 13, 2019 10:45AM - 10:57AM |
B17.00001: The properties of binary black holes observed by LIGO and Virgo Christopher P L Berry The LIGO–Virgo gravitational-wave detector network has now observed 10 binary black hole coalescences. By comparing the measured signal with model templates we can infer the properties of the source systems. These can be used to constrain the astrophysics of binary black hole formation and evolution. I will review the techniques used to make these inferences, and highlight some of the interesting results obtained from our catalogue of discoveries. |
Saturday, April 13, 2019 10:57AM - 11:09AM |
B17.00002: Rates of Compact Binary Mergers from LIGO-Virgo's First and Second Observing Runs Shasvath J Kapadia Estimating the rates of compact binary mergers from gravitational-wave (GW) data produced by the LIGO-Virgo network of ground based detectors is an important science target of the LIGO-Virgo collaboration (LVC), given that such rates could help inform the construction of models of stellar mass binaries. In this talk, we describe the Poisson-statistics-based formalism used to compute these rates. From data acquired during the first and second observing runs (O1 and O2) and analyzed by the GstLAL pipeline, we estimate posterior probability distributions on the astrophysical rates of mergers for three distinct classes of compact binaries, as well as assign, to candidate events, source-specific probabilities of their astrophysical origin. We find the rate of binary black hole mergers and binary neutron star mergers, at 90% confidence, to be 9−100/Gpc^3/yr and 97−3140/Gpc^3/yr, respectively, and a 90% upper limit on the rate of neutron star black hole mergers to be 610/Gpc^3/yr. |
Saturday, April 13, 2019 11:09AM - 11:21AM |
B17.00003: Using Gravitational Waves to Observe the Black Hole Mass Gap due to Pair-Instability Supernovae Daniel Finstad, Christopher Biwer, Laura K. Nuttall, Duncan A. Brown, Chris Fryer It has been suggested that the pair-instability mechanism could prevent the formation of black holes between 50 and 130 solar masses. In this talk, we assess the capability of the Advanced LIGO and Advanced Virgo detectors at design-sensitivity to observe this gap in the black hole mass function. We simulate a population of binary black hole mergers and use Bayesian inference to measure the component masses of the population. The resulting posterior distributions are used to determine if a mass gap can be observed from measurements, and we compare our results to previously observed astrophysical events by ground-based gravitational-wave detectors. |
Saturday, April 13, 2019 11:21AM - 11:33AM |
B17.00004: Characterization of low-significance gravitational-wave compact binary sources Yiwen Huang, Hannah Middleton, Ken K. Y. Ng, Salvatore Vitale, John Veitch LIGO and Virgo will start their third observing run in early 2019. Given our current rate estimates, we expect the detection of a binary black hole signal every week. The majority of these sources will be far away, and thus have low signal-to-noise ratios (SNRs). In this talk, we show if and to which extent the physical parameters of neutron stars and black holes in binaries can be measured at low SNRs. We find that subthreshold binary neutron stars, with SNRs below 12 (10), yield uncertainties in their sky position larger than 400 (700) deg^{2} (90% credible interval), allowing electromagnetic follow-ups by wide-field/all-sky survey instruments. The luminosity distance, which could be used to measure the Hubble constant with standard sirens, has relative uncertainties larger than 40% for binary neutron stars and neutron star black hole mergers. We will also show that we may be able to recover some information for intrinsic parameters, masses and spins, at SNRs as low as 6, but multimodality is not uncommon and can significantly broaden the posteriors. For spins, in particular, the uncertainty is higher for systems with comparable component masses or lack of spin precession. |
Saturday, April 13, 2019 11:33AM - 11:45AM |
B17.00005: Measurement of sub-dominant harmonic modes for gravitational-wave emission from a population of binary black holes Brendan D O'Brien Measurements of multiple harmonic modes in the gravitational wave signals from binary black hole events could provide an accurate test of general relativity, however they have never been observed. The sub-dominant modes, other than the main (l = 2, m = 2) mode, are weak in amplitude and thus difficult to detect in a single event at the current sensitivity of the gravitational-wave detectors. To recover sub-dominant modes, we propose an unmodeled method for summation of signals from a population of binary black holes. The method coherently stacks all signal modes, so the amplified signal can be extracted from the noisy data. To test the method, we consider a population of binary black holes and use the coherent WaveBurst algorithm for signal detection and reconstruction. With no a priori information about the signal model, we determine the transformation to coherently synchronize the merger and post-merger of one signal to another. We demonstrate the synchronization of multiple signals and show the efficient stacking of the (2, 2) mode and the sub-dominant modes. |
Saturday, April 13, 2019 11:45AM - 11:57AM |
B17.00006: Binary Black Hole gravitational waveform reconstruction with minimal morphological assumptions Sudarshan Ghonge, James Alexander Clark, Katerina Chatziioannou, Laura Cadonati The recently published catalog of Gravitational Wave events by the LIGO Virgo Collaboration, GWTC-1, showcases ten Binary Black Hole (BBH) sources whose signal waveforms were recovered using General Relativity (GR) template-based analyses. The catalog also presents signal reconstructions for these events using wavelet-based analyses that make minimal morphological assumptions. These analyses look for short duration, burst-like transients that appear coherently in the data of multiple detectors. Being agnostic to the precise morphology of the waveform, they can in principle offer waveform reconstructions that are robust to modeling errors, offering the potential to verify the presence of higher mode content or deviations from GR, for example. We find the waveforms reconstructed by morphology independent and templated analyses to be consistent within known errors, which lends credence to the inferred parameters and nature of these systems. |
Saturday, April 13, 2019 11:57AM - 12:09PM |
B17.00007: Impact of higher-modes and merger modeling for GW150914 & GW170104 Prayush Kumar, Jonathan Blackman, Scott E Field, Mark Scheel, Chad Galley, Michael Boyle, Lawrence E Kidder, Harald P Pfeiffer, Bela Szilagyi, Saul A Teukolsky Gravitational-wave detectors have begun observing coalescences of heavy ($\gtrsim 50-60M_\odot$) binary black holes (BBH) at a consistent pace for the past few years. A high level of waveform template accuracy is required for unbiased and precise estimation of source parameters for such BBH signals. Numerical relativity (NR) continues to provide the most accurate waveforms, especially when it comes to capturing nonlinear general relativistic effects near merger and subdominant waveform modes. Recently developed NR surrogate models interpolate these NR waveforms over the BBH parameter space while preserving NR-level accuracy. They therefore facilitate direct application of NR information to Bayesian parameter inferencing on BBH signals for the first time without additional approximations. In this talk we present a re-analysis of the first two heavy BBH mergers, GW150914 & GW170104, with NR surrogates. While the impact of both higher-modes and improved merger modeling on the GW signal itself is small, we find that their inclusion can shift posterior densities substantially for various parameters, especially source location and orientation, as well as the effective spin of the binary. |
Saturday, April 13, 2019 12:09PM - 12:21PM |
B17.00008: The impact of higher modes for GW170729 Jacob A Lange, Juan Calderón Bustillo, Katerina Chatziioannou, Roberto Cotesta, Sudarshan Ghonge, Sebastian Khan, Michael Pürrer, Salvatore Vitale GW170729 is a binary black hole merger recently announced by the LIGO Scientific and Virgo Collaborations (LVC). Its large detector-frame mass increases the relative impact of higher harmonics. In the paper announcing the discovery of this signal, the LVC comments on the modest impact of higher modes using analyses available at the time. We present a more thorough reanalysis of this event using the latest models and numerical-relativity waveforms with and without higher modes. We conclude that while the impact of higher modes is small, the inclusion of them shifts the posterior densities for various parameters. We find an increase in support for unequal masses and zero effective spin when higher modes are included for all waveform families. |
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