Bulletin of the American Physical Society
APS April Meeting 2022
Volume 67, Number 6
Saturday–Tuesday, April 9–12, 2022; New York
Session Q16: Gravitational Wave Detection with LISARecordings Available
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Sponsoring Units: DGRAV DAP Chair: Nicolas Yunes, University of Illinois at Urbana-Champaign Room: Sky Lobby |
Monday, April 11, 2022 10:45AM - 10:57AM |
Q16.00001: Bayesian Time Delay Interferometry Jessica Page, Tyson Littenberg Laser frequency noise (LFN) is the dominant source of noise expected in the Laser Interferometer Space Antenna (LISA) mission, at 107 orders of magnitude greater than the typical signal expected from gravitational waves (GWs). Time-delay interferometry (TDI) suppresses LFN to an acceptable level by linearly combining measurements delayed by durations that correspond to their relative separations. Knowledge of the delay durations is crucial for TDI effectiveness. This work extends upon previous studies using data-driven methods for inferring the delays during the post-processing of raw data, also known as TDI ranging (TDIR). Our TDIR analysis uses Bayesian methods designed to ultimately be included in the LISA data model as part of a ``Global Fit'' analysis pipeline. This allows for GW inferences which are marginalized over uncertainty in the spacecraft separations and independent estimation of the spacecraft orbits. We demonstrate Markov Chain Monte Carlo (MCMC) inferences of the six time-independent delays required in the rigidly rotating approximation of the spacecraft configuration (TDI 1.5) using simulated data. The MCMC uses fractional delay interpolation (FDI) to digitally delay the raw phase meter data, and we study the sensitivity of the analysis to the filter length. Varying levels of complexity in the noise covariance matrix are also examined. Delay estimations are found to result in LFN suppression well below the level of secondary noises and constraints on the armlengths to Ο(30) cm over the 2.5 Gm baseline. An outlook towards current work in implementing time-dependent delays (TDI 2.0) to account for the orbital motion of the spacecraft is provided. |
Monday, April 11, 2022 10:57AM - 11:09AM |
Q16.00002: Gravitational Wave Sources in A Time Varying Background Matthew C Digman, Neil J Cornish A unique challenge for LISA data analysis is that the noise backgrounds from instrumental noise and astrophysical sources will change significantly over both the year and the entire mission. The variation in the amplitude of the galactic stochastic GW background from galactic binaries as the antenna pattern rotates relative to the galactic center is a particularly significant component. LISA's sensitivity to different source classes will therefore vary as a function of sky location and time. The variation will impact both overall signal-to-noise and the efficiency of alerts to EM observers to search for multi-messenger counterparts. In this talk, I will discuss a wavelet-based technique for extracting sources from a time-varying background and discuss the impact on searches for various kinds of sources. |
Monday, April 11, 2022 11:09AM - 11:21AM |
Q16.00003: Where are you? How fast do you spin? Bayesian parameter estimation on a population of massive black-hole binaries using an inspiral-merger-ringdown waveform model with higher harmonics Roberto Cotesta, Alexandre Toubiana, Sylvain Marsat, Emanuele Berti, John G Baker The loudest gravitational-wave transient signals that the LISA interferometer will detect are expected to be emitted by the coalescence of massive black-hole binaries (MBHBs) with masses 105 ≤ M ≤ 109 Msun and redshifts 0.5 ≤ z ≤ 3. For these systems, it is important to precisely measure the black-hole masses and spins, and their sky positions. Indeed, constraining masses and spins is crucial to understand the MBHB formation and evolution mechanism, and accurately localizing them can guide the identification of potential electromagnetic counterparts associated to the MBHB merger. In this talk, I will show to what extent LISA can measure the binary parameters of these systems (including masses, spins and sky positions). For this purpose, we perform a parameter estimation study of a large number of MBHBs to understand for which systems we can get the best measurements of their binary parameters. In particular, for each MBHB, we perform a Bayesian parameter estimation study employing the LISA response function, and using a waveform model that includes inspiral, merger, ringdown and the effect of higher harmonics. |
Monday, April 11, 2022 11:21AM - 11:33AM |
Q16.00004: Hunting for intermediate-mass black holes with LISA binary radial velocity measurements Vladimir Strokov, Giacomo Fragione, Kaze W. K Wong, Thomas Helfer, Emanuele Berti Despite their potential role as massive seeds for quasars, in dwarf galaxy feedback, and in tidal disruption events, the observational evidence for intermediate-mass black holes (IMBHs) is scarce. LISA may observe stellar-mass black hole binaries orbiting Galactic IMBHs, and reveal the presence of the IMBH by measuring the Doppler shift in the gravitational waveform induced by the binary's radial velocity. We estimate the number of detectable Doppler shift events and we find that it decreases with the IMBH mass. A few Galactic globular clusters (including M22 and ω Centauri) may produce at least one event detectable by LISA if they harbor an IMBH at their center. We also estimate the number of expected Doppler shift events for IMBHs wandering in the Milky Way as a result of the disruption of their parent clusters. If there is at least one binary black hole orbiting around each wandering IMBH (assuming each destroyed GC left behind an IMBH), LISA may detect tens of Doppler shift events from IMBHs wandering in our Galaxy, and produce a map of this elusive population. |
Monday, April 11, 2022 11:33AM - 11:45AM |
Q16.00005: Improved Modeling of Highly Eccentric EMRI Signal Confusion Noise for LISA Daniel J Oliver, Aaron D Johnson, Lena Janssen, Joel Berrier, Kostas Glampedakis, Daniel Kennefick Scattering events around a supermassive black hole (SMBH) will occasionally toss a stellar-mass compact object into an orbit around the SMBH, beginning what is known as an extreme mass ratio inspiral (EMRI). The early stages of such a highly eccentric EMRI will not produce detectable gravitational waves because the source will only be in a suitable frequency band briefly (close to peribothron) during each long-period orbit. However, if we consider an ensemble of such subthreshold sources, spread across the Universe, together they produce an unresolvable background noise that may obscure sources otherwise detectable by LISA, the proposed space-based gravitational wave detector. Previous studies of this EMRI signal confusion background used a Newtonian order approximation. We seek to improve this characterization by implementing numerical kludge waveforms from relativistic population models developed by a semi-relativistic code. We will be tracking the evolution of the black hole population from a redshift of z=0 to z~3 using the Illustris Project. This information will be combined with an estimate of the number of mergers of compact objects with the black holes per unit volume to estimate the number of events contributing to the signal confusion noise. |
Monday, April 11, 2022 11:45AM - 11:57AM |
Q16.00006: Measuring accretion-disk effects with extreme-mass-ratio inspirals Andrea Antonelli Extreme-mass-ratio inspirals (EMRIs) are binary systems in which a small compact object orbits into a supermassive black hole. They are primary targets for the planned LISA mission, since the precision of their measured parameters allows for unparalleled tests of general relativity, as well as astrophysical and cosmological inference. Because of this, EMRI waveforms must be very accurate to capture deviations from general-relativistic predictions due to either modifications of the theory of gravity or the environs of the central supermassive black hole. In this talk I discuss how future detections of EMRIs can be used to measure parameters related to the accretion disks surrounding the massive black hole in the binary. The effects taken into consideration (and included in state-of-the-art EMRI models) are planetary-type migration, winds and dynamical friction. All of these lead to potentially large modifications of the secondaries' trajectories that depend on the accretion-disk parameters. I will present order-of-magnitude estimates for the detectability of such parameters, alongside a more sophisticated Monte Carlo analysis for the most promising effect. |
Monday, April 11, 2022 11:57AM - 12:09PM |
Q16.00007: Multi-band Gravitational Wave Cosmography with Dark Sirens Brian C Seymour, Hang Yu, Yanbei Chen Gravitational waves might help resolve the tension between early and late Universe measurements of the Hubble constant. Recently, there has been enhanced interest in the possibility of gravitational wave detectors in the deci-hertz band which bridges the gap between LISA and ground-based detectors. Such a detector is particularly suitable for the multi-band observation of stellar-mass black hole binaries between space and ground, which would significantly improve the source localization accuracy thanks to a long baseline for timing triangulation, hence promoting the "dark siren" cosmology. Proposed deci-hertz concepts include DECIGO/B-DECIGO, TianGO, and others. We consider here the multi-band observation of dark-siren binaries using TianGO at 0.1-10 Hz and a network of LIGO Voyagers at 10-100 Hz. We find that this configuration can uniquely identify a black-hole binary to a single galaxy, and thus a dark siren behaves as if it had an electromagnetic counterpart. Considering only fully localized dark sirens, we use a Fisher matrix to estimate the error in the Hubble constant and matter density parameter. We find that a deci-hertz detector substantially improves our ability to measure cosmological parameters because it enables galaxies to be identified out to a larger distance without the systematics from statistical techniques. |
Monday, April 11, 2022 12:09PM - 12:21PM |
Q16.00008: Science potential for stellar-mass black holes as neighbors of Sgr A* Shammi Tahura, Zhen Pan, Huan Yang There is a possibility that stellar-mass black holes inhabit near the massive black hole Sgr A* that is located at the center of our galaxy. Such scenarios are motivated by the mass segregation of stellar-mass black holes on the massive end and disk migration if there were an active accretion flow near Sgr A*. In this talk, I will focus on applications of such objects as sources of space-borne gravitational wave detector LISA. In particular, I will discuss the prospect of measuring the spin of Sgr A* with gravitational waves observations with LISA. I will further discuss the possibility of detecting the signature of dark matter clouds around Sgr A* as well as multi-body gravitational interactions. |
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