Bulletin of the American Physical Society
APS April Meeting 2017
Volume 62, Number 1
Saturday–Tuesday, January 28–31, 2017; Washington, DC
Session E5: Getting a Handle on the Population of Merging Binaries |
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Sponsoring Units: DAP DGRAV Room: Virginia B |
Saturday, January 28, 2017 3:30PM - 3:42PM |
E5.00001: Discriminating Formation Channels of Binary Black Hole Systems with Advanced LIGO Michael Zevin, Carl Rodriguez, Chris Pankow, Vicky Kalogera, Fred Rasio The field of gravitational-wave astronomy has been initiated by the recent observations of binary black hole mergers. These observations illuminate objects that are inaccessible with electromagnetic telescopes, and open inquiries as to how heavy binary black hole systems form and merge. Two possible formation channels proposed for such systems are isolated binary evolution in galactic fields and dynamical formation in star clusters. Currently, the coarse localization of these gravitational-wave events cannot indicate the environment in which the binary formed, and the mass distributions and merger rates from simulations of the aforementioned formation channels do not have an appreciable difference. However, the component spins of the black holes have the potential to unveil the formation history of the system. In this talk, I will discuss how to match measurements of the black hole component spin alignment with the projected spin distributions produced by population synthesis simulations. Using this framework we will link the estimated black hole spin to the formation channel of a merger, thus leading to a more detailed picture of their environments and origins. [Preview Abstract] |
Saturday, January 28, 2017 3:42PM - 3:54PM |
E5.00002: Studying Variance in the Galactic Ultra-compact Binary Population Shane Larson, Katelyn Breivik In the years preceding LISA, Milky Way compact binary population simulations can be used to inform the science capabilities of the mission. Galactic population simulation efforts generally focus on high fidelity models that require extensive computational power to produce a single simulated population for each model. Each simulated population represents an incomplete sample of the functions governing compact binary evolution, thus introducing variance from one simulation to another. We present a rapid Monte Carlo population simulation technique that can simulate thousands of populations on week-long timescales, thus allowing a full exploration of the variance associated with a binary stellar evolution model. [Preview Abstract] |
Saturday, January 28, 2017 3:54PM - 4:06PM |
E5.00003: The Binary Black Hole Merger Rate from Ultraluminous X-ray Source Progenitors Justin Finke, Soebur Razzaque Ultraluminous X-ray sources (ULXs) exceed the Eddington luminosity for an approximately 10 solar mass black hole. The recent detection of a black hole merger event GW 150914 by the gravitational wave detector ALIGO indicates that black holes with mass greater than 10 do indeed exist. Motivated by this, we explore a scenario where ULXs consist of black holes formed by the collapse of high-mass, low-metallicity stars, and that these ULXs become binary black holes (BBHs) that eventually merge. We use empirical relations between the number of ULXs and the star formation rate and host galaxy metallicity to estimate the ULX formation rate and the BBH merger rate at all redshifts. This assumes the ULX rate is directly proportional to the star formation rate for a given metallicity, and that the black hole accretion rate is distributed as a log-normal distribution. We include an enhancement in the ULX formation rate at earlier epochs due to lower mean metallicities. Our model is able to reproduce both the rate and mass distribution of BBH mergers in the nearby universe inferred from the detection of GW 150914, LVT 151012, and GW 151226 by LIGO if the median accretion rate of ULXs is a factor 1 to 30 greater than the Eddington rate. Our predictions of the BBH merger rate, mass distribution [Preview Abstract] |
Saturday, January 28, 2017 4:06PM - 4:18PM |
E5.00004: Detecting binarity of GW150914-like lenses in gravitational microlensing events Michael Kesden, Daniel Eilbott, Alexander Riley, Jonathan Cohn, Lindsay King The recent discovery of gravitational waves from stellar-mass binary black holes (BBHs) provided direct evidence of the existence of these systems. These BBHs would have gravitational microlensing signatures that are, due to their large masses and small separations, distinct from single-lens signals. We apply Bayesian statistics to examine the distinguishability of BBH microlensing events from single-lens events under ideal observing conditions, using modern photometric and astrometric capabilities. Given one year of ideal observations, a source star at the Galactic center, a GW150914-like BBH lens (total mass 65 solar masses, mass ratio 0.8) at half that distance, and an impact parameter of 0.4 Einstein radii, we find that BBHs with separations down to 0.00634 Einstein radii are detectable, marginally below the separation at which such systems would merge due to gravitational radiation with the age of the Universe. [Preview Abstract] |
Saturday, January 28, 2017 4:18PM - 4:30PM |
E5.00005: Measurement of Quasi Normal Modes for a population of Binary Black Hole Mergers Carlos Filipe Da Silva Costa, Sergey Klimenko, Shubhanshu Tiwari Perturbed solutions of the Kerr Black Hole (BH) are superimposition of damped sinusoids, named Quasi Normal Modes (QNM). These modes are completely defined by the final black hole parameters, mass and spin. Numerical simulations support that Binary BHs (BBH), after merging, produce a final BH emitting gravitational waves as described by the QNMs. This signal is very weak and hence the extraction of a QNM is quite challenging for the current generation of the ground based detectors. I will present a method for extraction of superimposed QNMs from future multiple observations of BBH merger signals in the advanced interferometers. We show that we can coherently sum up QNMs from the different signals and measure QNM parameters to prove the Kerr nature of a detected BHs population. [Preview Abstract] |
Saturday, January 28, 2017 4:30PM - 4:42PM |
E5.00006: Gravitational Wave Multi-Messenger Prospects for Pulsar Timing Arrays Joseph Simon, Sarah Burke-Spolaor Pulsar Timing Array (PTA) experiments are currently setting limits on the gravitational wave (GW) emission in the nanohertz frequency band. The primary source of GW emission in this band is expected to be a population of binary supermassive black holes (SMBHs) that form following galactic mergers. This population of binary supermassive black holes is representative of a crucial step in galaxy formation theories. During this process, there is the potential for many electromagnetic tracers to accompany the binary's evolution. In this talk, I will present recent work investigating the potential for jointly detecting a binary's electromagnetic and gravitational radiation. Such `multi-messenger' sources would provide a unique window into a pivotal stage of galaxy evolution, and would revolutionize the understanding of late-stage galaxy evolution. [Preview Abstract] |
Saturday, January 28, 2017 4:42PM - 4:54PM |
E5.00007: Dispersion Measure Variations in the NANOGrav 9-Year Data Release Megan Jones, Maura McLaughlin, Michael Lam, Jim Cordes, Lina Levin The principal goal of the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) is to detect gravitational waves in the nanohertz regime of the gravitational wave spectrum using a pulsar timing array (PTA). In order to detect gravitational waves, we must construct an accurate timing model that accounts for all known effects on the pulsar times-of-arrival (TOAs) over decade timescales. One of the parameters that must be fit in the timing model is the dispersion measure (DM). When the pulsar signal propagates through the ISM, interactions with free electrons cause dispersion that is characterized by a frequency dependent time delay. This time delay can be significant when compared to the pulsar period, and therefore must be fit when creating a timing model. We analyze DM variations of 37 milliseconds pulsars in the 9-year NANOGrav data release and constrain the sources of these variations. We fit for trends in DM measurements with time to measure the scale and periodicity, if any, of the variations. We present the structure functions of these DM time series and compare them to that expected for a Kolmogorov medium. We discuss explanations for any departures. [Preview Abstract] |
Saturday, January 28, 2017 4:54PM - 5:06PM |
E5.00008: Looking for angular information in the nHz gravitational wave background with harmonic space analysis of redshift maps Elinore Roebber, Gilbert Holder I will discuss an alternate framework for treating the angular information in the nanohertz gravitational wave background (GWB). Population models suggest that the GWB produced by binary supermassive black holes will be mostly confused, but that individual frequency bins may be dominated by a single loud source. We consider two toy models to span the range of resolvable to confused GWBs: a single source and a statistically isotropic Gaussian random field. In our alternate framework we treat both cases consistently by analyzing the full-sky redshift field induced by the GWs at the earth in harmonic space. As an example of the utility of this approach, the power spectrum of the redshift maps is the harmonic space analogue of the Hellings and Downs curve. Variance in the redshift power spectrum allows us to characterize the expected variance around the Hellings and Downs curve. [Preview Abstract] |
Saturday, January 28, 2017 5:06PM - 5:18PM |
E5.00009: Are LIGO's Black Holes Made from Smaller Black Holes? Maya Fishbach, Daniel Holz, Ben Farr We consider the hierarchical merger model for the formation of stellar mass black holes (such as the binary black holes observable by LIGO). In the hierarchical merger model, each black hole in a black hole binary is the result of a merger of two lesser black holes from a previous generation, and the previous generation's black holes may themselves be merger products of an even earlier generation. We apply the formulas of Hofmann, Barausse and Rezzolla (2016) to show that if black holes form in this hierarchical merger scenario, their spin magnitudes follow a certain probability distribution. We demonstrate how to compare this spin distribution to LIGO spin measurements in order to constrain the hierarchical merger scenario. [Preview Abstract] |
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