Bulletin of the American Physical Society
APS April Meeting 2021
Volume 66, Number 5
Saturday–Tuesday, April 17–20, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session Q09: Gravitational Wave Astronomy: Results and InterpretationLive
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Sponsoring Units: DAP Chair: Ingrid Stairs, UBC |
Monday, April 19, 2021 10:45AM - 10:57AM Live |
Q09.00001: Reanalyzing the properties of GW170817 and GW190425 with higher order modes Jacob Lange, Richard O'Shaughnessy, Kevin Barkett, Scott Field, Vijay Varma On August 17, 2017 and April 25, 2019, the LIGO-Virgo Collaboration (LVC) detected its first and second significant binary neutron star systems (BNS) via gravitational wave radiation. The subsequent event and catalog papers to follow used state-of-the-art semi-analytical tidal models that included only the dominant (2,2) mode to estimate the parameters of these systems. Since then, more novel models have been developed to include subdominant modes in its waveform. In this talk, I present a reanalysis of these two events using two of these novel models: a hybrid NR surrogate that includes tidal terms (NRHybSur3dq8Tidal) and a newer version of the effetive-one-body model that includes adiabatic tides (TEOBResumS v2). These new analyses give some insight into the importance of subdominant modes in estimating the parameters of BNS systems. [Preview Abstract] |
Monday, April 19, 2021 10:57AM - 11:09AM Live |
Q09.00002: GW190521 may be an intermediate mass ratio inspiral Collin Capano, Alex Nitz GW190521 was the first confident gravitational wave observation with a total mass greater than 100 solar masses. Initial estimates of the initial black holes place one or both of them in the upper mass gap produced by pair-instability in supernovae (~50-120 solar masses). We re-analyze GW190521 and find that there are additional modes in the mass distribution which are consistent with both black holes existing outside this mass gap, with the most likely parameters consistent with a ~16 solar mass black hole merging with a 170 solar mass black hole. I'll discuss these results and the implications for the history of GW190521. [Preview Abstract] |
Monday, April 19, 2021 11:09AM - 11:21AM Live |
Q09.00003: GW190521 as a Highly Eccentric Black Hole Merger Imre Bartos The stellar-mass black hole merger GW190521 is the heaviest system discovered by LIGO/Virgo so far, with masses unexpected from stellar evolution. The system underwent precession due to its black hole spin orientation, a signature of binaries formed through gravitational capture. Capture through close encounters can also lead to eccentric binary orbits, but this feature is currently difficult to identify due to the lack of suitable gravitational waveforms. I will discuss results showing that GW190521 is most consistent highly eccentric black hole merger. Eccentricity is expected from dynamical encounters with a high number density of black holes. Such a scenario is also consistent with the observed high mass and high precessing spin of GW190521. [Preview Abstract] |
Monday, April 19, 2021 11:21AM - 11:33AM Live |
Q09.00004: Eccentric-orbit extreme-mass-ratio inspirals: Analytic expansion in the conservative sector of black hole perturbation theory to high PN order Christopher Munna, Charles Evans We present new advances in determining analytic PN series for extreme-mass-ratio inspirals on a Schwarzschild background. We focus on a pair of gauge invariant quantities, the redshift invariant and spin-precession invariant, which help encode the conservative dynamics of these binaries under first-order black hole perturbation theory. The PN series are pursued using direct expansion of the MST solutions to the RWZ equations, along with a PN ansatz solution for RWZ equations with large mode number $l$. We compute the redshift invariant to 8.5PN through 20th order in eccentricity, finding that at multiple PN orders the eccentricity expansion exhibits a structured appearance which permits the extraction of a compact eccentricity function. Then, we utilize similar techniques to determine the spin-precession invariant to 6.5PN through 16th order in eccentricity. We conclude by discussing future applications to the more complicated Kerr problem. [Preview Abstract] |
Monday, April 19, 2021 11:33AM - 11:45AM Live |
Q09.00005: The Parents of LIGO Black Holes and Their Hometown Vishal Baibhav Two of the dominant channels to produce black-hole binary mergers are believed to be the isolated evolution of stellar binaries in the field and dynamical formation in star clusters. Pair instabilities prevent stellar collapse from generating black holes more massive than about 45-60 solar mass. This “mass gap” only applies to the field formation scenario: repeated mergers in clusters can fill the gap. A similar reasoning applies to the binary’s spin parameters. If black holes are born slowly rotating, the high-spin portion of the parameter space (the “spin gap”) can only be filled by black-hole binaries that are assembled dynamically. I will discuss how such signatures are a smoking gun for the hierarchical origin, and how recent detections (GW190521 and GW190412) fit in this context. I will also talk about how we may be able to reconstruct the properties of progenitors of second-generation black holes. [Preview Abstract] |
Monday, April 19, 2021 11:45AM - 11:57AM Live |
Q09.00006: Measurement of intermediate mass black hole binaries including the mass gap in the upcoming LIGO-Virgo observations Ajit Mehta, Alessandra Buonanno, Jonathan Gair, Cole Miller, Richard deBoer, Michael Wiescher, Frank Timmes, Eb Farag The formation mechanism, evolutionary history and mass function of intermediate mass black holes (IMBHs) are still not well known, as it is very difficult to observe them and measure their masses in the electromagnetic window. In this work, we explore the possibility to measure source parameters of IMBH binaries via gravitational waves in upcoming O4 LIGO-Virgo observation. We perform parameter estimation (PE) on a large set of non-precessing IMBH binaries and show that primary source mass can typically be measured with accuracy $10\sim 40\%$, far better than what might be possible by electromagnetic observations of such binaries. A particular subset of IMBH population in mass range $ \sim 50-130 M_{\odot}$ is prohibited from the stellar evolution theory due to what is known as the pair production instability. The limits of this mass range, however, are subject to uncertainties in nuclear reaction rates. In this work, we also perform evolution of massive Helium stars using MESA stellar evolution code to understand the susceptibility of mass gap range to plausible changes in these nuclear rates. Having established the mass gap range, we perform PE study and show that upcoming LIGO-Virgo detectors are capable of robustly identifying binaries with components lying in the mass gap. [Preview Abstract] |
Monday, April 19, 2021 11:57AM - 12:09PM Live |
Q09.00007: The Heaviest Black Holes of LIGO/Virgo Gayathri Vivekananthaswamy Recently, the LIGO and Virgo gravitational-wave observatories discovered a black hole merger, GW190521, with a total mass of about 150 solar masses. LIGO/Virgo are sensitive to mergers with total mass up to 1000 solar masses, providing a window onto intermediate-mass black hole mergers in this mass range, probing whether the black hole mass distribution continues to higher masses. The origin of the heaviest black holes with mass above 50 solar masses is debated. The heaviest ones like GW190521 likely are not the end products of stellar evolution but could have been forged by multiple previous mergers in galactic centers, globular clusters of AGN disks. Here, we discuss what we learned from LIGO/Virgo's published results about the heaviest events and what expect in the future. [Preview Abstract] |
Monday, April 19, 2021 12:09PM - 12:21PM Live |
Q09.00008: Interpreting the Gravitational Wave Background in Terms of Supermassive Black Hole Binary Populations J. Andrew Casey-Clyde, Chiara Mingarelli, Jenny Greene, Andy Goulding, Kris Pardo To date, most models of the stochastic gravitational wave background (SGWB) have built up their supermassive black hole binary (SMBHB) populations by modeling the merger histories of massive galaxies to $z \sim 1$. However, recent observations of dual AGN systems have opened up the possibility of using quasar population models as a proxy for massive black hole binary populations, such as the one developed by Goulding et al. (2019). We build on this quasar-backed approach by using estimates of the local number of binary sources from Mingarelli et al. (2017) to tie this model to observables in a self-consistent way. We additionally allow the black hole mass function to evolve with redshift, reflecting changes in the properties of the SMBHB population. The resulting SGWB amplitude is found to be comparable to models based on major mergers, and we offer a comparison of both types of models to results from the NANOGrav 12.5-yr dataset. We note systematic differences between the SMBHB populations implied by each type of model as well as differences in their evolution over cosmic time and compare the two differing populations. Finally, we explore avenues by which these differences might be reconciled to describe a single population of SMBHBs which contribute to the SGWB. [Preview Abstract] |
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