Bulletin of the American Physical Society
APS April Meeting 2017
Volume 62, Number 1
Saturday–Tuesday, January 28–31, 2017; Washington, DC
Session R3: Black Holes and Their Environments |
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Sponsoring Units: DAP DGRAV Chair: Neil Cornish, Montana State University Room: Maryland C |
Monday, January 30, 2017 10:45AM - 10:57AM |
R3.00001: The Effect of Supermassive Black Hole Binary Environments on Time to Detection for the Stochastic Background Sarah Vigeland, Xavier Siemens Pulsar timing arrays (PTAs) are sensitive to the gravitational wave (GW) stochastic background produced by supermassive black hole binaries (SMBHBs). Environmental effects such as gas and stars accelerate the evolution of SMBHBs and may deplete the stochastic background at low frequencies. How much this effects the sensitivity of PTAs to the stochastic background depends on the astrophysical mechanism and where the binary's evolution transitions from being driven by environmental effects to driven by GW emission. We will discuss how these issues impact our observing strategy and estimated time-to-detection. [Preview Abstract] |
Monday, January 30, 2017 10:57AM - 11:09AM |
R3.00002: Efficiently Simulating the Evolution of Massive Black Holes, and Implications for NANOGrav and LISA Sean McWilliams The coalescence of massive black-hole binaries is the principle target source for existing pulsar timing arrays (PTAs) like NANOGrav, and future spaced-based observatories like LISA. For the very massive sources that occur in the PTA band, the massive elliptical host galaxies are thought to evolve primarily through mergers, whereas at the lower masses that will be observed by LISA, other factors such as star formation and accretion must be accounted for. We discuss a novel approach to simulate this evolution that avoids expensive numerical simulations by calibrating to galaxy observations, but which ensures a self-consistent merger model by requiring that the sum of all effects on galaxy and black hole growth actually yield the galaxy evolution that we observe. By optimizing this new approach, we are able to simulate many realizations of the Universe, including a variety of evolutionary scenarios, and what impact they have on the signal observable by PTAs. We will also discuss the extension of this approach to predicting LISA event rates, and the challenges that must be overcome if we are to reliably simulate this lower mass population. [Preview Abstract] |
Monday, January 30, 2017 11:09AM - 11:21AM |
R3.00003: Constraining stellar binary black hole formation scenarios with LISA eccentricity measurements Emanuele Berti, Atsushi Nishizawa, Alberto Sesana, Antoine Klein A space-based interferometer such as LISA could observe few to few thousands progenitors of black hole binaries (BHBs) similar to those recently detected by Advanced LIGO. Gravitational radiation circularizes the orbit during inspiral, but some BHBs retain a measurable eccentricity at the low frequencies where LISA is most sensitive. The eccentricity of a BHB carries precious information about its formation channel: BHBs formed in the field, in globular clusters, or close to a massive black hole (MBH) have distinct eccentricity distributions in the LISA band. We generate mock LISA observations, folding in measurement errors, and using Bayesian model selection we study whether LISA measurements can identify the BHB formation channel. We find that a handful of observations would suffice to tell whether BHBs were formed in the gravitational field of a MBH. Conversely, several tens of observations are needed to tell apart field formation from globular cluster formation. A five-year LISA mission with the longest possible armlength is desirable to shed light on BHB formation scenarios. [Preview Abstract] |
Monday, January 30, 2017 11:21AM - 11:33AM |
R3.00004: Radiation Transport in Dynamic Spacetimes Jeremy Schnittman, John Baker, Zachariah Etienne, Bruno Giacomazzo, Bernard Kelly We present early results from a new radiation transport calculation of gas accretion onto merging binary black holes. We use the Monte Carlo radiation transport code Pandurata, now generalized for application to dynamic spacetimes. The time variability of the metric requires careful numerical techniques for solving the geodesic equation, particularly with tabulated spacetime data from numerical relativity codes. Using a new series of general relativistic magneto-hydrodynamical simulations of magnetized flow onto binary black holes, we investigate the possibility for detecting and identifying unique electromagnetic counterparts to gravitational wave events. [Preview Abstract] |
Monday, January 30, 2017 11:33AM - 11:45AM |
R3.00005: Distinguishing transients from merger characteristics in EM signals from black hole binary mergers. Bernard Kelly, Zachariah Etienne, Bruno Giacomazzo, John Baker, Jeremy Schnittman The merger of comparable-mass black holes is already known to produce extremely high luminosity in the form of gravitational waves, offering a prime target to current and future interferometric gravitational-wave detectors. Such mergers will often take place in plasma-rich environments, leading to the exciting possibility of concurrent electromagnetic merger signals that can be analyzed by traditional astronomical facilities. While mergers in magnetized plasmas are generically expected to produce jet-like structures, there is little consensus about the formation and detailed nature of these jets. We report on simulations in 3D general relativistic ideal MHD of the merger of equal-mass binaries, each initially immersed in a homogeneous fluid with a uniform magnetic field aligned with the orbital axis. In particular, by simulating a series of binaries at different initial separations, we are able to distinguish between transient features characteristic of frame-dragging of the plasma and later features correlated with the merger itself. [Preview Abstract] |
Monday, January 30, 2017 11:45AM - 11:57AM |
R3.00006: Effects of Inner Alfv\'{e}n Surface Location on Black Hole Magnetospheres in the Force-Free Limit Kevin Thoelecke, Masaaki Takahashi, Sachiko Tsuruta An energy extracting black hole magnetosphere can be defined by the location of its inner Alfv\'{e}n surface, which determines the rate of energy extraction along a given magnetic field line that passes through it. Despite its defining role, it is still largely uncertain how the location and nature of the inner Alfv\'{e}n surface might correspond to changes in magnetosphere structure. In this talk I will present simple force-free black hole magnetospheres obtained numerically that encompass a wide range of Alfv\'{e}n surface locations. In particular the differences between magnetospheres with an Alfv\'{e}n surface near the horizon and an Alfv\'{e}n surface near the boundary of the ergoregion will be discussed, along with what those differences might imply about energy extracting black hole magnetospheres in general. [Preview Abstract] |
Monday, January 30, 2017 11:57AM - 12:09PM |
R3.00007: The population of low-mass X-ray binaries ejected from black-hole retaining globular clusters Matthew Giesler, Drew Clausen, Christian Ott The fate of stellar-mass black holes (BHs) formed in globular clusters (GCs) is still widely uncertain; recent studies suggest that GCs may retain a substantial population of BHs, in contrast to the long held belief of a few to zero BHs. We model the population of BH low-mass X-ray binaries (BH-LMXB) ejected from GCs that are representative of Milky Way GCs with variable BH populations. We simulate the formation of BH-binaries in GCs through exchange interactions between binary and single stars in the company of tens to hundreds of BHs. We construct Monte Carlo realizations of the present day BH-LMXB population that account for both the binary evolution of the ejected systems and the dynamical evolution of these binaries in the Milky Way potential. We find that the orbital parameters of the ejected binaries are sensitive to both the GC's observable structural parameters and its unobservable BH population. Our results suggest that these dynamically formed BH-LMXBs will be easily distinguishable, by their distinctive kinematic properties and larger BH masses, from those produced in the field. Identifying this population of BH-LMXBs, an ideal observable proxy for elusive single BHs, would provide observational constraints on the GC BH retention fraction. [Preview Abstract] |
Monday, January 30, 2017 12:09PM - 12:21PM |
R3.00008: Gravitational waves from a plunge into a nearly extremal Kerr black hole Lior M. Burko, Gaurav Khanna We study numerically in the time domain the linearized gravitational waves emitted from a plunge into a nearly extremal Kerr black hole by solving the inhomogeneous Teukolsky equation in the extreme mass-ratio domain. We consider spinning black holes for which the specific spin angular momentum $a/M=1-\epsilon$, and we consider values of $\epsilon\geq 10^{-6}$. We find an effective transient behavior for the quasi-normal ringdown: the early phase of the quasi-normal ringdown is governed by a decay according to inverse time, with frequency equaling twice the black hole's horizon frequency. Our results confirm that a similar phenomenon, first found by Yang, Zimmerman, and Lehner for source-free scalar fields, occurs also for sourced gravitational waves. We find that the smaller $\epsilon$ the later the transition from this transient inverse time decay to exponential decay. Such sources, if exist, may be interesting potential sources for terrestrial or space borne gravitational wave observatories. We briefly discuss some of the observational features of such sources for gravitational-wave astronomy, extending previous results by Gralla, Hughes, and Warburton for the ``smoking gun" features of such sources from the pre-ISCO phase of the coalescence to the ringdown phase. . [Preview Abstract] |
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