Bulletin of the American Physical Society
APS April Meeting 2023
Volume 68, Number 6
Minneapolis, Minnesota (Apr 15-18)
Virtual (Apr 24-26); Time Zone: Central Time
Session Q08: Laser Interferometer Space Antenna |
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Sponsoring Units: DGRAV Chair: Davide Gerosa, University of Milan, Bicocca Room: Symphony III - 2nd Floor |
Monday, April 17, 2023 3:45PM - 3:57PM |
Q08.00001: The LISA Global Fit Neil J Cornish, Tyson Littenberg The LISA space based gravitational wave observatory will open up the source-rich milli-Hertz band of the gravitational wave spectrum. The rich LISA data set will pose the unique challenge of having to disentangle thousands of overlapping signals, while also dealing with data gaps and non-stationary noise. To avoid bias, multiple signals and noise have to be fit simultaneously. I will describe the first prototype LISA Global Fit pipeline, which uses trans-dimensional Bayesian inference to simultaneously fit for thousands of compact galactic binaries, dozens of massive black hole mergers, and instrument noise. |
Monday, April 17, 2023 3:57PM - 4:09PM |
Q08.00002: LISA Global Fit Data Analysis with a Wavelet Domain Python Pipeline Matthew C Digman, Neil J Cornish The Laser Interferometer Space Antenna (LISA) will produce three TDI channels simultaneously containing all LISA gravitational-wave sources. The data from all astrophysical source classes will overlap, including galactic binaries (GBs), stellar origin black hole binaries (SOBHBs), supermassive black hole binaries (SMBHBs), and extreme mass ratio inspirals (EMRIs). Parameter estimation and search pipelines must fit all sources simultaneously in a global fit to the entire data stream. The limiting noise for LISA in some wavelengths will be the stochastic combination of astrophysical gravitational wave sources, making effective simultaneous global source extraction critical for all LISA science cases. Achieving high computational efficiency of the pipeline is essential to alert LISA's multi-messenger search partners as quickly as possible; slow alerts could result in irreversible loss of multi-messenger observations. Furthermore, efficient pipelines can substantially reduce expenditure on computational resources. In this work, I present an efficient wavelet-domain Python code with demonstrated flexibility to conduct parameter estimation for all these source classes within the same infrastructure. I will show the power of our pipeline to handle non-stationary noise and assess how the pipeline can provide value to LISA's multi-messenger and multi-wavelength observing partners. |
Monday, April 17, 2023 4:09PM - 4:21PM |
Q08.00003: 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 noise used a Newtonian order approximation. We seek to improve this characterization by implementing numerical kludge waveforms from relativistic population models. The waveforms were developed by a semi-relativistic code and are fully evolved inspirals from capture to the separatrix with the intent of fully exploring the orbital space. 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 17, 2023 4:21PM - 4:33PM |
Q08.00004: Early warning search for LISA massive black holes Debnandini Mukherjee, Tyson Littenberg, Neil J Cornish The space based laser interferometer LISA, expected to be operational in the next decades, will be able to probe the millihertz frequency band. This will make it sensitive to a vast array of compact object mergers, including the massive black holes or MBHs. These black holes, straddling the intermediate and supermassive types of black holes, have masses extending above a minimum of 1000 solar mass. They are expected to be observable within the LISA band for several weeks to months before they merge. This makes them excellent candidates for low latency, pre-merger observations. Also, some mergers of MBHs are expected to have electromagnetic counterparts due to the presence of gas or disks. Pre-merger alerts with sky location information from LISA data analysis sent out to the astronomy community, would enable early detections of such mergers in multiple electromagnetic bands. Such multimessenger observations stand to further our knowledge of astrophysics, including that of black hole formation and evolution. In my talk we explore the possibility of sending out such pre-merger alerts, using a simulated LISA training data set. |
Monday, April 17, 2023 4:33PM - 4:45PM |
Q08.00005: Detection of Gravitational memory effect in LISA using triggers from ground-based detectors. Sourath T Ghosh, Alex J Weaver, Jose Sanjuan, Paul Fulda, Guido Mueller The LIGO-Virgo-Kagra (LVK) collaboration has detected gravitational waves from 90 Compact Binary Coalescences. In addition to fortifying the linearized theory of General Relativity (GR), the statistical ensemble of detections provides information on the astrophysics of the binary sources and prospects detect nonlinear effects predicted by GR. One such prediction is the effect of nonlinear gravitational memory, which is a permanent strain in space-time after the passage of the gravitational wave. For compact binary sources, the memory strain from individual detectors is about a couple of orders below the noise background. This fact motivates the idea of coherently stacking up data streams from recorded GW events so that the cumulative memory strain is detected with a high SNR. Additionally, since most of the energy is radiated at merger the strain induced by the memory effect resembles a step function at the merger time, thus making the stacking scheme much simpler (as opposed to stacking oscillating GW waveforms). Moreover, since the GW detectors essentially record the integrated strain response, the use of long arm interferometers is ideal to detect the memory effect at low frequency. LISA (Laser Interferometer Space Antenna) is a future space-based GW detector with arms oriented in an approximate equilateral triangle of length 2.5 Gm, sensitive in the 0.1 mHz to 1 Hz frequency range. In this talk, we propose a method which is designed to use the event catalog of ground-based detectors and search for corresponding memory strains in the LISA data stream. Additionally, given the LVK catalog and assuming certain source population models, we use scaling arguments to conservatively estimate the run time required for LISA to accumulate a memory SNR of 5, using triggers from future ground-based detectors. Finally, we extend these calculations for using beyond LISA missions like ALIA, AMIGO and FOLKNER to detect the gravitational memory effect. The results for LISA predict a detection of the memory effect within the 10 years lifetime while the corresponding results for beyond LISA missions are even more promising |
Monday, April 17, 2023 4:45PM - 4:57PM |
Q08.00006: LISA Constraints on an Intermediate-Mass Black Hole in the Galactic Center Vladimir Strokov, Giacomo Fragione, Emanuele Berti Nuclear star clusters in galaxies are among the potential hosts for intermediate-mass black holes (IMBHs). If present in a galactic nucleus, an IMBH will perturb the motion of other members of the nucleus. The absence of observable perturbations in our own Galactic center has resulted in a few constraints on the IMBH mass and position. In this work we show that Laser Interferometer Space Antenna (LISA) can help put complementary constraints if the IMBH forms a binary with a compact remnant (white dwarf, neutron star, or a stellar black hole). The gravitational-wave signal from the binary will exhibit Doppler-shift variations as the binary orbits around the supermassive black hole (SMBH) at the center of the Milky Way. The signal and its Doppler shift will help constrain the mass and position of the IMBH, respectively. We argue that this method is the most effective in a region of the parameter space which remains partially unconstrained: for IMBHs with masses between 103 and 105 solar masses and located between 0.1 mpc and 2 mpc from the SMBH. We show that in this region, if the binary is detected, its Doppler shift is most likely measurable. We also discuss possible ways for an IMBH to form a binary in the Galactic center, and we argue that the most efficient channel is gravitational-wave captures of stellar black holes and neutron stars. |
Monday, April 17, 2023 4:57PM - 5:09PM |
Q08.00007: Assessing the accuracy limitations of existing waveforms on the data analysis of potential LISA sources. Aasim Z Jan, Jacob A Lange, Deborah Ferguson, Deirdre M Shoemaker Future detectors such as LISA will have unprecedented sensitivities enabling us to detect binary black hole coalescences with relatively high signal-to-noise ratios (SNRs), from hundreds to potentially in the thousands for some sources. With this significant increase in the SNR, it is expected that the current accuracies of numerical relativity (and in turn model) waveforms will not be sufficient and introduce systematic errors. In this talk, we present results from our study on the impact of systematic biases introduced by numerical relativity waveforms and the dependent models on the data analysis of potential LISA gravitational wave sources. |
Monday, April 17, 2023 5:09PM - 5:21PM |
Q08.00008: BHPWave: A perturbative gravitational waveform model for rotating black holes Zachary Nasipak We present BHPWave, a new open-source waveform model that uses black hole perturbation theory to simulate the gravitational wave signals of stellar-mass compact objects undergoing quasi-circular inspirals into rotating massive black holes. These so-called extreme-mass-ratio inspirals (EMRIs) will be ideal sources for future mHz gravitational wave detectors, such as LISA. Designing fast and accurate EMRI waveforms is critical to observing these systems. However, few open-access EMRI waveform generators currently exist, and those that do exist are either `kludge' models that rely on non-relativistic approximations or relativistic models that are restricted to non-rotating black holes. BHPWave bridges this gap by providing a freely-available generator that simulates EMRIs using the Teukolsky formalism and the adiabatic approximation from black hole perturbation theory. By restricting to quasi-circular inspirals, BHPWave can produce year-long signals in seconds in the time-domain or frequency-domain for EMRIs with dimensionless massive black hole spins between 0 and 0.995. In this talk we discuss the novel methods underlying BHPWave and how they might be applied to future EMRI waveform models. We also use BHPWave to demonstrate how errors in perturbation data impact the accuracy of EMRI gravitational waveforms. |
Monday, April 17, 2023 5:21PM - 5:33PM |
Q08.00009: Extending second-order self-force calculations to Kerr spacetime Andrew Spiers, Jordan E Moxon, Adam Pound Black hole perturbation theory has recently offered exciting progress in modelling the binary problem using the self-force approach. First-post adiabatic self-force waveforms for quasi-circular inspirals in Schwarzschild spacetime have shown remarkable agreement with Numerical Relativity, even in the 1:10 mass ratio regime. The dissipative second-order self-force is a crucial contribution to these waveforms. However, extending second-order calculations to Kerr spacetime offers many barriers. This talk presents my progress in overcoming some of these barriers. I discuss how multiple second-order Teukolsky equations exist, how to make their sources well-defined in the self-force problem, and how to avoid divergences. One key advantage of the Teukolsky equation is its separability. However, the lack of symmetry of the Kerr metric seemingly prevents the separability of generic Teukolsky sources without expensive numerical calculations. I present a method for analytically separating generic sources in Kerr spacetime to a given accuracy. |
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