Bulletin of the American Physical Society
APS April Meeting 2022
Volume 67, Number 6
Saturday–Tuesday, April 9–12, 2022; New York
Session D15: Gravitational Wave Sources and PopulationsRecordings Available
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Sponsoring Units: DAP DGRAV Chair: Colm Talbot, Massachusetts Institute of Technology Room: Soho |
Saturday, April 9, 2022 1:30PM - 1:42PM |
D15.00001: Stellar Wind Effects Of The Wolf-Rayet Star in IC 10 X-1 Sayantan Bhattacharya, Silas G. T. Laycock, Andre-Nicolas Chene, Breanna A Binder, Dimitris M Christodoulou We studied how the stellar wind is affected by the black hole's accretion flow in IC 10 X-1 and similar WR+BH HMXB systems, the origin and evolution of the He ii 4686 emission line, and its credibility in determining the binary parameters. IC 10 X-1 has been one of the major targets to many GEMINI observations spanning 2001-19. |
Saturday, April 9, 2022 1:42PM - 1:54PM |
D15.00002: Astrophysical lessons from the population of merging compact binaries in GWTC-3 Amanda Farah The third Gravitational Wave Transient Catalog (GWTC-3) considerably expands on the number of compact binary coalesces from the previous LIGO-Virgo-KAGRA catalog, and is the first to contain all three classes of detectable binary mergers: binary black holes, binary neutron stars, and neutron star-black holes. |
Saturday, April 9, 2022 1:54PM - 2:06PM |
D15.00003: Inferring the Neutron Star Maximum Mass and Lower Mass Gap in Neutron Star–Black Hole Systems with Spin Christine Ye, Maya Fishbach Gravitational-wave (GW) detections of merging neutron star--black hole (NSBH) systems provide a new way to probe the 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, which probes the mysterious nature of high-density nuclear matter, and a potential mass gap between the maximum NS mass and the minimum BH mass, which probes probes the uncertain supernova explosion mechanism. Previous GW measurements of the NS mass distribution have assumed nonspinning NSs; however, rapidly spinning NSs, if they exist, can extend to larger maximum masses and may appear to fill in the mass gap. This is particularly relevant in light of the recent GW detection of either the most massive NS or the lightest BH -- a 2.6 solar mass object in the event GW190814 -- which several authors have proposed is a rapidly spinning NS. In this work, we explore whether the spin-dependent NS maximum mass and the lower mass gap can be inferred in spinning NSBH systems. We jointly model the NS spin distribution and the NSBH mass distribution, and apply the inference to four LIGO--Virgo NSBH detections and simulated future GW data. We find that current NSBH events support a mass gap, although GW190814's nature remains unclear. Both the mass gap width and NS maximum mass vary with spin assumptions; in particular, estimates of the maximum mass when including or excluding GW190814 differ, but this tension is partially resolved if GW190814 is assumed to have significant spin. Under simplified assumptions, 150 future NSBH events may constrain the maximum nonspinning NS mass to $\pm0.02\,M_\odot$, and we may even measure the relation between the NS maximum mass and NS spin entirely from GW data. We show that if rapidly rotating NSs exist, the NS spin and mass distributions must be modeled simultaneously to avoid biasing inference of the NS maximum mass. |
Saturday, April 9, 2022 2:06PM - 2:18PM |
D15.00004: Hierarchical Inference of Binary Neutron Star Mass Distribution and Equation of State with Gravitational Waves Jacob Golomb, Colm Talbot Gravitational wave observations of binary neutron star mergers provide valuable information about neutron star structure and the equation of state of dense nuclear matter. Numerous methods have been proposed to analyze the population of observed neutron stars and previous work has demonstrated the necessity of jointly fitting the astrophysical distribution and the equation of state in order to accurately constrain the equation of state. In this work, we introduce a new framework to simultaneously infer the distribution of binary neutron star masses and the nuclear equation of state using Gaussian mixture model density estimates which mitigates some of the limitations previously-used methods suffer from. Using our method, we reproduce previous projections for the expected precision of our joint mass distribution and equation of state inference with tens of observations. We also show that mismodeling the equation of state can bias our inference of the neutron star mass distribution. While we focus on neutron star masses and matter effects, our method is widely applicable to population inference problems. |
Saturday, April 9, 2022 2:18PM - 2:30PM |
D15.00005: Sources of systematic error in gravitational-wave measurements of the binary neutron star mass distribution Andrea S Biscoveanu, Colm Talbot, Salvatore Vitale The binary neutron star (BNS) mass distribution measured with gravitational-wave observations has the potential to reveal information about the dense matter equation of state, supernova physics, the expansion rate of the universe, and tests of General Relativity. As most current gravitational-wave analyses measuring the BNS mass distribution do not simultaneously fit the spin distribution, the implied population-level spin distribution is the same as the spin prior applied when analyzing individual sources. In this talk, we will demonstrate that introducing a mismatch between the implied and true BNS spin distributions can lead to biases in the inferred mass distribution due to the correlation between mass ratio and spin for individual sources. We will show that applying a low-spin prior which excludes the true spin magnitudes of some sources in the population leads to significantly overestimating the maximum neutron star mass and underestimating the minimum neutron star mass at the population level with as few as six BNS detections. We find that the safest choice of spin prior that does not lead to biases in the inferred mass distribution is one which allows for high spin magnitudes and tilts misaligned with the orbital angular momentum. |
Saturday, April 9, 2022 2:30PM - 2:42PM |
D15.00006: The Mass Distribution of Neutron Stars in Gravitational-wave Binaries Philippe Landry, Jocelyn S Read The discovery of two neutron star-black hole coalescences by LIGO and Virgo brings the total number of likely neutron stars observed in gravitational waves to six. We perform the first inference of the mass distribution of this extragalactic population of neutron stars. In contrast to the bimodal Galactic population detected primarily as radio pulsars, the masses of neutron stars in gravitational-wave binaries are thus far consistent with a uniform distribution, with a greater prevalence of high-mass neutron stars. The maximum mass in the gravitational-wave population agrees with that inferred from the neutron stars in our Galaxy and with expectations from dense matter. |
Saturday, April 9, 2022 2:42PM - 2:54PM |
D15.00007: Translating inferences between eccentric gravitational waveform models Alan Knee, Isobel M Romero-Shaw, Paul D Lasky, Eric Thrane, Jessica McIver Orbital eccentricity is a key signature of dynamical binary black hole (BBH) formation. The gravitational waves from a coalescing binary contain information about its orbital eccentricity, which can be measured if the binary retains sufficient eccentricity close to merger. Measurements of eccentricity require accurate inspiral-merger-ringdown waveform models that incorporate eccentric dynamics. Several models are in good agreement with numerical relativity and have been used to constrain the eccentricities of BBH candidates detected during the first three LIGO/Virgo observing runs. However, these models define eccentricity in disparate ways, posing a challenge to obtaining meaningful eccentricity measurements. We present studies that map these conflicting waveform definitions to each other, and show how this information can be leveraged for parameter estimation. |
Saturday, April 9, 2022 2:54PM - 3:06PM |
D15.00008: The evolution of compact object mergers and their host galaxies across cosmic time Filippo Santoliquido The next-generation network of gravitational wave observatories are expected to detect many more compact object mergers inside their host galaxies. In light of this future circumstances, I developed a theoretical tool that investigates the properties of formation and host galaxies of compact objects. The starting point of my new methodology is a population of star-forming galaxies across cosmic time obtained from observed scale relations. I varied the metallicity of galaxies, considering the fundamental metallicity relation (FMR) and the mass-metallicity relation (MZR). With my fast methodology, we are also able to compare different populations of compact objects. In this talk, we will see the impact of different population-synthesis simulations, where I varied the value of the alpha common envelope (alpha_CE = 1, 3 and 5). I evaluated the merger rate density of compact objects for this set of models and I compared it with the 90% credibile intervals inferred by the LIGO-Virgo-KAGRA collaboration. We will see how different metallicity distributions strongly affect the merger rate density evolution of binary black holes (BBHs) with redshift. By looking at the properties of host galaxies, I learnt that low mass galaxies with stellar mass < 10^9 solar masses can host up to 50% of the total BBH mergers, with alpha_CE = 1. For larger masses, the merger rate per galaxy correlates with stellar mass of galaxies for all compact objects types. Moreover, the typical masses of the host galaxies increase significantly as we approach the local Universe. An indicator of this trend is the rise in percentage of compact object mergers hosted in passive galaxies, which can be > 80% for alpha_CE = 5. |
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