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 X09: Gravitational Wave Astronomy: Future and TheoryLive
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Sponsoring Units: DAP Chair: Maya Fishbach, Northwestern University |
Tuesday, April 20, 2021 10:45AM - 10:57AM Live |
X09.00001: Comparing Single-Source Statistics for Pulsar Timing Array Observing Strategies Jeffrey Hazboun, Joseph Romano With the recent detection of a common, low frequency signal in the NANOGrav 12.5-year data set, pulsar timing arrays are moving closer toward a significant detection of a stochastic gravitational background from supermassive binary black holes. Once the stochastic background is observed, it is expected that the first detections of single sources will happen shortly thereafter. These sources will allow for long-lived monitoring of continuous gravitational waves, and may provide unprecedented multimessenger information about active galactic nuclei. The time is now to decide on pulsar observing strategies focused on detecting these sources. The use of sensitivity curves allows an efficient way to develop and compare the multitude of observing strategies available to PTAs. Here we compare the various statistics that exist in the literature for continuous sources and discuss their use in constructing sensitivity curves for existing and proposed PTA observational strategies. [Preview Abstract] |
Tuesday, April 20, 2021 10:57AM - 11:09AM Live |
X09.00002: Systematic Uncertainty of Standard Sirens From the Viewing Angle of Binary Neutron Star Inspirals Hsin-Yu Chen The joint detection of gravitational-wave and electromagnetic-wave emissions from neutron star mergers GW170817 allowed for the first standard-siren measurement of the Hubble constant. Future standard sirens will potentially shed light on the tension between the local distance ladders and Planck experiments. Therefore, thorough understanding of the sources of systematic uncertainty for the standard siren method is crucial. In this talk, I will discuss a systematic uncertainty of the standard siren method introduced by the aspherical electromagnetic emission of neutron star mergers. Depending on the observational strategies and the understanding of the electromagnetic emissions, the systematics originated from the geometry of electromagnetic emissions of neutron star mergers may be a major challenge before the standard sirens can resolve the tension in Hubble constant. [Preview Abstract] |
Tuesday, April 20, 2021 11:09AM - 11:21AM Live |
X09.00003: Astrophysics Milestones for PTAs Nihan Pol, Stephen Taylor, Luke Kelley, Sarah Vigeland, Joseph Simon, Siyuan Chen The NANOGrav Collaboration found strong Bayesian evidence for a common-spectrum stochastic process in its 12.5-yr pulsar timing array (PTA) dataset. However, evidence for the quadrupolar Hellings \& Downs interpulsar correlations was not yet significant. We emulate and extend the NANOGrav dataset, injecting a wide range of stochastic gravitational wave background (GWB) signals that encompass a variety of amplitudes and spectral shapes. We then apply our standard detection pipeline and explore three key astrophysical milestones: (I) robust detection of the GWB; (II) determination of the source of the GWB; and (III) measurement of the properties of the GWB spectrum. Given the amplitude measured in the 12.5 yr analysis and assuming this signal is a GWB, we expect to accumulate robust evidence of an interpulsar-correlated GWB signal with 15--17 yrs of data, i.e., an additional 2-5 yrs from the 12.5 yr dataset. At the initial detection, the achieved fractional uncertainty should be sufficient to distinguish a SMBHB source for the background from other, more exotic, sources. We also show that it is possible to distinguish power-law models from those with a spectral turn-over with 20 yrs of data. Finally, with the IPTA data combination, these milestones will be achieved much earlier. [Preview Abstract] |
Tuesday, April 20, 2021 11:21AM - 11:33AM Live |
X09.00004: Constraining the SMBHB population with the nanohertz GWB Joseph Simon, Luke Kelley, Siyuan Chen, Nihan Pol, Stephen Taylor, Sarah Vigeland The NANOGrav Collaboration has found strong evidence for a common-spectrum process in its most recent pulsar timing dataset, however, lacking evidence for a quadrupolar correlation signature, the result remains ambiguous with respect to the presence of a gravitational wave background (GWB). Assuming that this is indeed the first hints of an astrophysical GWB and that it is built up from the cosmic population of supermassive black hole binaries (SMBHBs), it is important to understand what we can expect to learn about the SMBHB population in the coming years. To that end, we have emulated and extended the NANOGrav dataset, injecting a wide range of GWB signals from simulated populations of SMBHBs, which we recover using NANOGrav's detection pipeline. In this talk, I will discuss our results to three main questions: (i) how constraining is the initial parameter estimation derived from the GWB, (ii) how robust is that parameter estimation across different model assumptions, and (iii) how do initial constraints improve over time? [Preview Abstract] |
Tuesday, April 20, 2021 11:33AM - 11:45AM Live |
X09.00005: The Logic of Detection: Statistics and Systematics in the Search for Gravitational Waves with Pulsar-Timing Arrays Michele Vallisneri The first detection of gravitational waves by LIGO was graced by overwhelming statistical confidence, setting a challenging but (I argue) misleading precedent for ongoing analysis with pulsar-timing-array data: in fact the general acceptance of LIGO's claim relied on crucial lines of evidence beyond statistics, and fewer ``sigmas'' would have sufficed. I outline a defensible standard for future claims that pulsar timing arrays have observed the stochastic gravitational-wave background from supermassive black-hole binaries, addressing the peculiarities of pulsar-timing campaigns, including the formulation of a detection hypothesis, the difficulty of establishing a null background, the possibility of confounding systematics, and more. [Preview Abstract] |
Tuesday, April 20, 2021 11:45AM - 11:57AM Live |
X09.00006: Compact binary populations following O3a Daniel Wysocki With the publication of GWTC-2, the ever-growing catalog of gravitational wave detections has grown formidable in size. With the addition of tens of confident detections, our ability to discern between candidate population models has grown. In step with that has come a need for increased modeling complexity. In this presentation, we explore some of the latest developments in modeling compact binary populations, and the astrophysical implications of GWTC-2. [Preview Abstract] |
Tuesday, April 20, 2021 11:57AM - 12:09PM Live |
X09.00007: Characterizing High Mass Binary Black Hole Signals with RIFT: Applications of Cutting Edge Parameter Estimation Techniques Richard Udall, Karan Jani, Jacob Lange, Bhavesh Khamesra, Hyun Choi, Grihith Manchanda, James Clark, Richard O'Shaughnessy, Deirdre Shoemaker, Laura Cadonati, Kelly Holley-Bockelmann, Pablo Laguna The coalescences of exceptionally massive binaries such as GW190521 and GW170502 are among the most interesting events observable by ground based gravitational wave observatories in the LVK network. In particular, it is known that higher order modes and spin precession are more likely to affect parameter estimation for these systems, and that they are among the best test cases for numerical relativity and numerical relativity derived surrogate models. RIFT (Rapid parameter Inference on gravitational wave sources via iterative Fitting) is a parameter estimation algorithm which allows rapid exploration of the parameter space and computation of likelihoods for competing models, making it well suited to this application. I will discuss the use of these techniques with this exciting class of events, including their application to real data for the events mentioned above, as well as investigations into the systematics of parameter estimation on these systems. [Preview Abstract] |
Tuesday, April 20, 2021 12:09PM - 12:21PM Live |
X09.00008: NANOGrav Constraints on Fuzzy Dark Matter Brendan Drachler The nature of dark matter remains one of the most perplexing questions in all of astrophysics. The proposed candidates of dark matter currently range from macroscopic objects down to the lowest energy particles ever proposed to exist. Among the many candidates in the low-energy spectrum is fuzzy dark matter (FDM), also called ultralight scalar dark matter, which consists of axions with masses on the order of $10^{-23}$ eV. The oscillation of the FDM scalar field’s pressure can induce oscillations in the gravitational potential which is predicted to be detectable by pulsar timing arrays. We will present results on a search for FDM using the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) 12.5 year dataset as well as a retroactive search using the NANOGrav 11 year dataset. We will also present upper limits on the amplitude and frequency of the oscillations in the gravitational potential, and use the upper limits to constrain the possible mass of the FDM axions. [Preview Abstract] |
Tuesday, April 20, 2021 12:21PM - 12:33PM Live |
X09.00009: Effects of higher order modes in gravitational-wave inference of signals from binary neutron star mergers A. B. Yelikar, A. Z. Jan, J. Lange, R. O'Shaughnessy When estimating the properties of binary neutron stars via gravitational wave radiation, it is vital to use the most accurate and physically-motivated models available. Even with the most sophisticated models, deviations can introduce bias in the parameter estimation between different models. In this talk, I present work that investigates systematic differences between tidal waveform models that include higher-order modes. This work quantifies the systematics between different models and between the inclusion and omission of higher-order modes. We also describe the performance of efforts to mitigate these biases by marginalizing over different waveform families [Preview Abstract] |
Tuesday, April 20, 2021 12:33PM - 12:45PM Live |
X09.00010: Tidal Deformation and Dissipation of Rotating Black Holes Horng Sheng Chia Black holes are never isolated in realistic astrophysical environments; instead, they are often perturbed by complicated external tidal fields. How does a black hole respond to these tidal perturbations? In this talk, I will discuss both the conservative and dissipative responses of the Kerr black hole to a weak and adiabatic gravitational field. The former describes how the black hole would change its shape due to these tidal interactions, and is quantified by the so-called ``Love numbers''. On the other hand, the latter describes how energy and angular momentum are exchanged between the black hole and its tidal environment due to the absorptive nature of the event horizon. I will show that the Love numbers of the Kerr black hole vanish identically --- in other words, you cannot stretch a black hole. I will also describe how the Kerr black hole's dissipative response implies that energy and angular momentum can either be lost to or extracted from the black hole, with the latter process commonly known as the black hole superradiance. Finally, I will discuss how these tidal responses leave distinct imprints on the gravitational waves emitted by binary black holes. [Preview Abstract] |
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