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 D09: Tides and Equation of State in Compact Binaries |
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Sponsoring Units: DGRAV Chair: Steven Liebling, Long Island University Room: Conrad B/C - 2nd Floor |
Saturday, April 15, 2023 3:45PM - 3:57PM |
D09.00001: Breaking Bad Degeneracies with Love: Improving gravitational-wave measurements through universal relations Yiqi Xie, Deep Chatterjee, Gilbert Holder, Daniel Holz, Scott E Perkins, Kent Yagi, Nicolas Yunes The distance-inclination degeneracy limits gravitational-wave parameter estimation of compact binary mergers. Such a degeneracy can be partially broken by including higher-order modes or precession when modeling the waveform of a binary that contains a black hole. But what about binary neutron stars, for which these effects are suppressed? In this talk, I will introduce a new parameterization of the tidal effects in the binary neutron star waveform, exploiting the binary Love relations, that breaks the distance-inclination degeneracy. The binary Love relations prescribe the tidal deformability of a neutron star as a function of its source-frame mass in an equation-of-state insensitive way, and thus allows direct measurement of the redshift of the source. If the cosmological parameters are assumed to be known, the redshift can be converted to a luminosity distance, and the distance-inclination degeneracy can thus be broken. With the distance better constrained, one may also be able to measure the source-frame masses to higher precision. I will demonstrate this new approach with a range of binary neutron-star observing scenarios using Bayesian parameter estimation on synthetic data. In particular, I will give a forecast about when and how much this new approach will improve real gravitational wave measurements of binary neutron stars. |
Saturday, April 15, 2023 3:57PM - 4:09PM |
D09.00002: Phase Transition Phenomenology with Nonparametric Representations of the Neutron Star Equation of State Reed Essick Astrophysical observations of Neutron Stars (NS) allow us to probe the properties of cold, dense nuclear matter, in particular whether there are phase transitions in the Equation of State (EoS) at high densities. Previous studies adopted ad hoc parametric models in attempt to capture particular features thought to be common to some phase transitions. However, such models can introduce strong priors on the types of behavior allowed within the EoS, and these assumptions may not be warranted. We, instead, avoid these issues by extracting features common to many phase transitions directly from the EoS without relying on an underlying parametrization. After introducing the new features, we show what current astrophysical data can say about the presence or absence of phase transitions at high densities. We also discuss prospects for measuring phase transitions in NSs with future catalogs of gravitational wave observations. |
Saturday, April 15, 2023 4:09PM - 4:21PM |
D09.00003: Testing Universal Relations under Nonparametric Equations of State Bubakar O Sy-Garcia Universal relations are proposed relationships between neutron star observables that are thought to hold regardless of the cold supranuclear equation of state. In this work, we use non-parametric equation of state models to test these relationships by implementing a measure of their goodness of fit as compared to astrophysical observability. Our model-agnostic approach allows us to more rigorously observe the equation of state independence present in these relations, by limiting the microscopic correlations due to nuclear modeling. We find relations between tidal deformability, moment of inertia, and the quadrupole moment are robust while other relations, such as between compactness and tidal deformability will require more analysis with third generation sensitivity. |
Saturday, April 15, 2023 4:21PM - 4:33PM |
D09.00004: Efficient fully precessing gravitational waveforms for binaries with neutron stars Michael Lahaye, Huan Yang, Béatrice P Bonga, Zhenwei Lyu We construct an efficient frequency domain waveform for generic circular compact object binaries that include neutron stars. The orbital precession is solved on the radiation reaction timescale (and then transformed to the frequency domain), which is used to map the non-precessional waveform from the source frame of the binary to the lab frame. The treatment of orbital precession is different from that for precessional binary black holes, as χeff is no longer conserved due to the spin-induced quadrupole moments of neutron stars. We show that the new waveform achieves ≤10-4 mismatch compared with waveforms generated by numerically evolved precession for neutron star-black hole systems for ≥90% configurations with component mass/spin magnitude assumed in the analysis and randomized initial spin directions. We expect this waveform to be useful to test the nature of the mass-gap objects similar to the one discovered in GW 190814 by measuring their spin-induced quadrupole moments, as it is possible that these mass-gap objects are rapidly spinning. |
Saturday, April 15, 2023 4:33PM - 4:45PM |
D09.00005: Beyond the linear tide: impact of the nonlinear tidal response of neutron stars on gravitational waveforms for binary inspirals Hang Yu, Nevin N Weinberg, Phil Arras, James Kwon, Tejaswi Venumadhav Tidal interactions in coalescing binary neutron stars modify the dynamics of the inspiral, and hence imprint a signature on their gravitational-wave (GW) signals in the form of an extra phase shift. We need accurate models for the tidal phase shift in order to constrain the supranuclear equation of state from observations. In previous studies, GW waveform models were typically constructed by treating the tide as a linear response to a perturbing tidal field. In this work, we incorporate nonlinear corrections due to hydrodynamic three- and four-mode interactions and show how they can improve the accuracy and explanatory power of waveform models. We set up and numerically solve the coupled differential equations for the orbit and the modes, and analytically derive solutions of the system's equilibrium configuration. Our analytical solutions agree well with the numerical ones up to the merger and involve only algebraic relations, allowing for fast phase shift and waveform evaluations for different equations of state over a large parameter space. We find that, at Newtonian order, nonlinear fluid effects can enhance the tidal phase shift by >~ 1 radian at a GW frequency of 1000 Hz, corresponding to a 10−20% correction to the linear theory. The scale of the additional phase shift near the merger is consistent with the difference between numerical relativity and theoretical predictions that account only for the linear tide. Nonlinear fluid effects are thus important when interpreting the results of numerical relativity, and in the construction of waveform models for current and future GW detectors. |
Saturday, April 15, 2023 4:45PM - 4:57PM |
D09.00006: Tidal Deformability and Electromagnetic Love Numbers of Magnetars Siddarth Ajith, Kent Yagi Finite-size effects, such as the tidal deformability of stellar bodies, are an excellent avenue to expand our understanding of both gravitational and nuclear physics. Information about the internal physics of stars is imprinted in gravitational wave signals, and knowledge about tidal effects is crucial for such studies. Perturbative models of neutron stars with electromagnetic fields, motivated by magnetars, have been extensively studied without tidal interactions. Thus, studying how these electromagnetic fields interact with tidal fields is worthwhile. We build on recent work that constructed a perturbative model of magnetized, tidally-deformed neutron stars by considering perturbations to the Maxwell field due to tidal interactions. We also extend the model by adding slow-rotation perturbations, which induce an electric field. This allows us to find modifications to the gravitational Love number of the star as well as a new electromagnetic field Love number. Both Love numbers vanish for Reissner-Nordström black holes, but the presence of matter in the neutron star case leads to interesting non-trivial results. These interactions between the tidal and electromagnetic fields can lead to measurable effects in double magnetar systems that may be observed using gravitational waves. |
Saturday, April 15, 2023 4:57PM - 5:09PM |
D09.00007: Measuring neutron star magnetism with graviational-wave observations. Carl-Johan O Haster, Kent Yagi From observing the gravitational waves emitted during a coalescence of a binary neutron star system it is possible to infer many of the properties of the neutron stars including their mass, spins and size (through measuring the neutron stars' tidal deformability). Observations of radio and X-ray pulsars have also shown that neutron stars harbour some of the strongest magnetic fields present in our Universe. In this presentation we explore the impact and measurability of the magnetic fields' strength, structure and orientation on the observed gravitational waves and what those measurements can tell us about the neutron star Equation of State. |
Saturday, April 15, 2023 5:09PM - 5:21PM |
D09.00008: Population properties and multimessenger prospects of neutron star–black hole mergers following GWTC-3 Andrea S Biscoveanu, Philippe Landry, Salvatore Vitale Neutron star-black hole (NSBH) mergers detected in gravitational waves have the potential to shed light on supernova physics, the dense matter equation of state, and the astrophysical processes that power their potential electromagnetic counterparts. In this talk, we will present constraints on the mass and spin distributions and multimessenger prospects of NSBH systems based on the population of four candidate events detected in gravitational waves so far with a false alarm rate ≤ 1 yr−1. Using an approach driven by gravitational-wave data rather than binary simulations, we will show that fewer than 14% of NSBH mergers detectable in gravitational waves will have an electromagnetic counterpart. Finally, we will describe a method for the multimessenger analysis of NSBH mergers based on the nondetection of an electromagnetic counterpart that allows us to place independent constraints on the neutron star equation of state. |
Saturday, April 15, 2023 5:21PM - 5:33PM |
D09.00009: The role of astrophysical effects in testing general relativity with gravitational waves from double white dwarfs Shu Yan Lau, Kent Yagi, Phil Arras Testing gravity beyond general relativity (GR) motivated by cosmological observations or quantum gravity has been of interest in theoretical physics. Although existing tests have provided stringent bounds on the discrepancies from GR, there is still plenty of room for certain theories to survive. Previous studies have shown that gravitational waves from galactic double white dwarfs can be a useful tool to constrain non-GR effects that are significant in relatively low-density regimes compared to neutron stars and black holes. Meanwhile, astrophysical effects such as self-rotations and tidal deformations also have a significant impact on the dynamics of these systems, thus adding complexity to the gravity tests. In this talk, I will present our study on the possible bounds we can place on the non-GR effects using gravitational waves from double white dwarfs. We employ a generic parametrized model for the non-GR corrections to the frequency evolution while taking into account the possible contaminations from astrophysical effects to estimate the bounds on the non-GR effect at different post-Newtonian order. We find that systematic errors due to the lack of astrophysical effects in waveform modeling can be comparable to statistical errors in certain cases. We also comment on how to apply this analysis to specific theories including the general screened modified gravity and theories involving axion, which are expected to deviate more from GR within white dwarfs than neutron stars and black holes. |
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