Bulletin of the American Physical Society
APS April Meeting 2018
Volume 63, Number 4
Saturday–Tuesday, April 14–17, 2018; Columbus, Ohio
Session G13: Gravitational Waves: Source Modeling - I |
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Sponsoring Units: DGRAV Chair: Scott Hughes, MIT Room: A224-225 |
Sunday, April 15, 2018 8:30AM - 8:42AM |
G13.00001: Gravitational wave searches for ultralight bosons with LIGO and LISA Emanuele Berti, Enrico Barausse, Richard Brito, Vitor Cardoso, Irina Dvorkin, Shrobana Ghosh, Antoine Klein, Paolo Pani Ultralight bosons can induce superradiant instabilities in spinning black holes, tapping their rotational energy to trigger the growth of a bosonic condensate. Possible observational imprints of these boson clouds include (i) direct detection of the nearly monochromatic (resolvable or stochastic) gravitational waves emitted by the condensate, and (ii) statistically significant evidence for the formation of ``holes'' at large spins in the spin versus mass plane (sometimes also referred to as ``Regge plane'') of astrophysical black holes. LIGO could observe a stochastic background of gravitational radiation in the range $m_s\in [2\times 10^{-13}, 10^{-12}]$~eV, and up to $10^4$ resolvable events in a $4$-year search if $m_s\sim 3\times 10^{-13}\,{\rm eV}$. LISA could observe a stochastic background for boson masses in the range $m_s\in [5\times 10^{-19}, 5\times 10^{-16}]$, and up to $\sim 10^3$ resolvable events in a $4$-year search if $m_s\sim 10^{-17}\,{\rm eV}$. LISA could further measure spins for massive black-hole binaries, either ruling out scalar fields in the mass range $\sim [4 \times 10^{-18}, 10^{-14}]$~eV, or measuring $m_s$ with ten percent accuracy if light scalars in the mass range $\sim [10^{-17}, 10^{-13}]$~eV exist. [Preview Abstract] |
Sunday, April 15, 2018 8:42AM - 8:54AM |
G13.00002: Detectability of gravitational waves from superradiant instabilities of scalar fields Shrobana Ghosh, Enrico Barausse, Emanuele Berti, Richard Brito, Vitor Cardoso, Irina Dvorkin, Antoine Klein, Paolo Pani, Mauricio Richartz Incident waves scattering off a black hole may get amplified at the expense of the rotational energy of the hole. Because of this process, known as superradiance, ultralight massive bosonic fields can form a non-axisymmetric cloud around the black hole due to repeated amplification. The growth of this bosonic cloud leads to emission of gravitational radiation, that could in principle be detected by ground-based gravitational wave detectors if the boson has mass $\sim 10^{-12}$eV or by LISA for masses $\sim 10^{-17}$eV. Therefore astrophysical black holes can serve as particle detectors. In the absence of detections, we can rule out the existence of bosons in the corresponding mass range. We explore near-term and long-term prospects for observing such events through follow-up searches of the continuous waves that would be emitted after black hole merger events of the kind detected by the LIGO/Virgo collaboration. [Preview Abstract] |
Sunday, April 15, 2018 8:54AM - 9:06AM |
G13.00003: Black hole spin evolution in black hole binaries Riccardo Barbieri, Davide Gerosa, Giovanni Rosotti The spin directions of a supermassive black hole binary before the merger are crucial parameters in influencing the emitted gravitational-wave signal and whether or not the post-merger black hole receives a kick strong enough to dislodge it from the host galaxy. The interaction between each black hole and its surrounding accretion disc is the key player in setting the spin directions. Lense-Thirring precession and gas accretion both act to align the black-hole spin angular momentum of the disc. We study the disc-spin alignment problem combining two approaches: (i) we first use semi-analytical solutions to capture the Lense-Thirring effect for each individual black hole and its surrounding material; we then (ii) perform a set of simulations with the GANDALF smoothed-particle hydrodynamics code to provide initial conditions to describe the binary systems. This two-step process critically allows us to capture all the relevant lengthscales of the problem. We finally discuss the implications of our findings in the context of LISA future detections of misaligned black hole binary mergers and their gravitational kicks. [Preview Abstract] |
Sunday, April 15, 2018 9:06AM - 9:18AM |
G13.00004: Exciting black hole modes via misaligned coalescences: I. Framework and inspiral/plunge worldline computation Anuj Apte, Scott Hughes The final gravitational waves emitted in the coalescence of two black holes are quasi-normal ringing modes of the merged remnant. The amplitudes of these modes are determined by the mass ratio of the system and the geometry of the coalescence. To simplify the analysis, we consider a small mass ratio system consisting of a non-spinning body of mass $\mu$ that inspirals on a quasi-circular trajectory into a massive Kerr black hole. Our goal is to understand how different modes are excited as a function of the black hole spin and an angle $\theta_{inc}$ which characterizes the misalignment of the orbit’s angular momentum with the black hole spin axis. In this talk, we sketch an overview of the calculation we have undertaken and present the details of its first step, computing the worldline the smaller body follows as it inspirals and plunges into the larger black hole. Our approach generalizes earlier work by Ori and Thorne. [Preview Abstract] |
Sunday, April 15, 2018 9:18AM - 9:30AM |
G13.00005: Exciting black hole modes via misaligned coalescences: II. Characterizing the mode content of late time coalescence waveforms Halston Lim, Gaurav Khanna, Scott Hughes Using the inspiral and plunge trajectory computed using a generalized version of the Ori-Thorne algorithm, we use a time-domain black hole perturbation theory code to compute the corresponding gravitational waves. The last cycles of these waveforms are a superposition of Kerr black hole quasi-normal modes. In this talk, we will present calculations of the ``excitation factors'' of quasi-normal modes, and will examine how the modes' excitations vary as a function of source parameters like the larger black hole's spin and the geometry of the smaller body's inspiral and plunge trajectory. Our results indicate that measuring multiple ringdown modes of black hole coalescence gravitational waves may provide useful information about the source's binary properties, such as the misalignment of the orbit's angular momentum with black hole spin. [Preview Abstract] |
Sunday, April 15, 2018 9:30AM - 9:42AM |
G13.00006: Recent progress in the effective source approach to the self-force problem with a time domain code Peter Diener, Barry Wardell, Niels Warburton, Anna Heffernan, Adrian Ottewill The effective source approach to the self-force problem have proven to be a very valuable tool in the effort to simulate Extreme Mass Ratio In-spiral (EMRI) systems consisting of a compact object in orbit around a super massive black hole at the center of a galaxy. Such systems are expected to be one of the primary sources for gravitational waves to be observed by LISA. In this talk, I will present a progress report on the development of a very accurate time domain code based on the Discontinuous Galerkin method for solving hyperbolic partial differential equations. In this code the small compact object (or particle) is described by an effective source. This ensures that, near the particle, only the regular part of the field is evolved. Thus, as the singular piece of the field is not present at the particle location, there is no need for mode sum regularization, allowing for simple extraction of the self-force. The ultimate goal of this project is to be able to evolve, in a self-consistent manner, both the fields and the orbit of an EMRI system. [Preview Abstract] |
Sunday, April 15, 2018 9:42AM - 9:54AM |
G13.00007: Recent work in gravitational-wave memory waveform calculations Marc Favata, Matthew Karlson, Kevin Chen, Lita de la Cruz The gravitational-wave memory is a time-varying but non-oscillatory contribution to the gravitational-wave signal. It can be produced by non-periodic source motions (unbound binaries, ejected matter/neutrinos) or nonlinear interactions of gravitational-waves with themselves. I will give an overview of several areas of development in computing memory waveforms, including (i) modeling the memory component of supernova simulations, (ii) comparing different approaches for computing memory waveforms in binary black hole collisions, and (iii) computing the memory in binary neutron star mergers. [Preview Abstract] |
Sunday, April 15, 2018 9:54AM - 10:06AM |
G13.00008: Inspirals into a charged black hole Ruomin Zhu, Thomas Osburn The effect of electric charge on gravitational wave observations involving compact binaries is investigated. Extreme and intermediate mass-ratio inspirals are modeled using a small mass-ratio approximation. We consider the case where the larger binary component is a Reissner-Nordstrom black hole and the smaller binary component is a neutral compact object. The effect of radiation reaction on the smaller body is quantified through calculation of electromagnetic and gravitational energy fluxes. Through this analysis we estimate the level of charge necessary to affect gravitational wave observations. [Preview Abstract] |
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