Bulletin of the American Physical Society
APS April Meeting 2013
Volume 58, Number 4
Saturday–Tuesday, April 13–16, 2013; Denver, Colorado
Session Q10: Gravitational Wave Observation |
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Sponsoring Units: GGR Chair: Gabriela Gonzalez, Louisiana State University Room: Governor's Square 12 |
Monday, April 15, 2013 10:45AM - 10:57AM |
Q10.00001: Searching for a stochastic gravitational-wave background from a population of neutron stars in the Virgo cluster with data from the LIGO and Virgo detectors Dipongkar Talukder We describe an in-progress search with LIGO and Virgo data for a stochastic gravitational-wave background (SGWB) from the population of rotating non-axisymmetric neutron stars in the Virgo cluster. Employing multi-baseline radiometry, bounds on the GW strain power from the Virgo cluster can be obtained, which, in turn, can constrain neutron star equations of state. The current status of the search will be presented. We also assess (a) the expected performance of this search using forthcoming second-generation detectors, including the improvement from locating one of the advanced LIGO detectors in India and (b) the reach of third generation detectors to astrophysical SGWBs. [Preview Abstract] |
Monday, April 15, 2013 10:57AM - 11:09AM |
Q10.00002: Observing spinning NSBH coalescences with second generation gravitational wave observatories Ian Harry, Duncan Brown, Drew Keppel, Andrew Lundgren, Alex Nitz In this talk we investigate the issues in observing Neutron-Star -- Black-hole binary coalesences with second generation gravitational wave observatories, when the components have spin. Previous searches for compact binary coalescences using first generation facilities neglected the effect of spin. We demonstrate that such an approach will not be sufficient in the advanced detector era. We discuss how to search for such systems using model waveforms that include spin effects, but do not include the effects of precession and demonstrate that this offers a significant improvement. We also discuss the importance of using an accurate waveform model and investigate how well currently available approximations agree with each other, thus motivating the need for these models to be extended to include higher-order terms. Finally we discuss the importance of precession and how it might be possible to detect highly precessing coalescences. [Preview Abstract] |
Monday, April 15, 2013 11:09AM - 11:21AM |
Q10.00003: Extracting equation of state parameters from black hole-neutron star mergers Benjamin Lackey, Koutarou Kyutoku, Masaru Shibata, Patrick Brady, John Friedman Information about the neutron-star equation of state is encoded in the waveform of a black hole-neutron star system through tidal interactions and the possible tidal disruption of the neutron star. During the inspiral this information depends on the tidal deformability $\Lambda$ of the neutron star, and we find that $\Lambda$ is the best measured parameter during the merger and ringdown as well. We have performed 134 simulations where we systematically varied the equation of state as well as the mass ratio, neutron-star mass, and black hole spin, and we have calibrated an inspiral-merger-ringdown waveform model to these simulations. We use this model to determine the measurability of $\Lambda$ as well as correlations with other waveform parameters for Advanced LIGO and the proposed Einstein Telescope. [Preview Abstract] |
Monday, April 15, 2013 11:21AM - 11:33AM |
Q10.00004: Searching for eccentric binary neutron star coalescences in Advanced LIGO. Eliu Huerta, Duncan Brown The coalescence of binary neutron stars is the primary source targeted by the Laser Interferometer Gravitational-wave Observatory (LIGO) and Virgo. Current searches for these systems assume that they will be on circular orbits when they enter Advanced LIGO's band ($\sim$ 15-1500 Hz), as expected for the observed binary pulsars that have evolved in the field. Several recent studies suggest that a population of binary neutron stars may also form by n-body interactions in core-collapsed globular clusters or in galactic nuclei near supermassive black holes and that these systems may have non-negligible eccentricity in the LIGO band. Optimal searches to detecting eccentric binaries or to place observational constraints on the rate requires template waveforms that capture the effect of eccentricity. For systems with total mass of 2.4 (6.0) solar masses, the effect of eccentricity e \textless\ 0.02 (0.05) is negligible and a circular search can effectively recover these events. For eccentricities up to e $=$ 0.4, we investigate the ability of searches using the post-circular expansion of Yunes et al. to detect eccentric systems and investigate the selection bias in searches for binaries with low to moderate eccentricities. [Preview Abstract] |
Monday, April 15, 2013 11:33AM - 11:45AM |
Q10.00005: Eccentric compact object mergers Frans Pretorius, William East, Janna Levin, Sean McWilliams, Kai Sheng Tai Stellar mass compact object mergers are one of the primary sources of gravitational wave emission that the ground-based gravitational wave detection effort is targeting. Furthermore, if one or both of the compact objects are neutron stars there is promise for coincident electromagnetic emission. Detection, and more importantly extracting properties of the merging system from observations requires theoretical knowledge of the characteristics of the emission. An interesting though possibly rare class of merger events are binaries that merge with large eccentricity. They could occur in close encounters in dense cluster environments, or in a hierarchical triple system subject to Kozai resonance. The gravitational wave signals are markedly different from quasi-circular inspirals, and template-based analysis strategies may not be ideal for eccentric mergers. I will describe ongoing numerical simulations of eccentric binary black hole, black hole-neutron star and binary neutron star systems highlighting some of the interesting dynamics, as well as early results of the efficacy of a stacked, excess power search strategy. [Preview Abstract] |
Monday, April 15, 2013 11:45AM - 11:57AM |
Q10.00006: When can gravitational-wave observations distinguish between black holes and neutron stars? Duncan Brown, Mark Hannam, Stephen Fairhurst, Chris Fryer, Ian Harry Gravitational-wave observations of compact binaries have the potential to uncover the distribution of masses and angular momenta of black holes and neutron stars in the universe. The binary's physical parameters can be inferred from their effect on the phasing of the gravitational-wave signal, but a partial degeneracy between the components' mass ratio and their angular momenta limits our ability to measure the individual component masses. At signal to noise ratios likely to be seen by advanced gravitational-wave detectors, we show that it will in many cases be difficult to distinguish whether the components are neutron stars or black holes. We identify when the masses of the binary components could be unambiguously measured outside the range of current observations. However, additional information would be needed to distinguish between a binary containing two $1.35$ M$_\odot$ neutron stars and an exotic neutron-star--black-hole binary. We also identify those configurations that could be unambiguously identified as black-hole binaries, and show how the observation of an electromagnetic counterpart to a neutron-star--black-hole binary could be used to constrain the black-hole spin. [Preview Abstract] |
Monday, April 15, 2013 11:57AM - 12:09PM |
Q10.00007: The Gravitational-Wave Signature of Core-Collapse Supernovae Christian D. Ott, Ernazar Abdikamalov, Sarah Gossan, Hannah Klion, Roland Haas, Philipp Moesta, Christian Reisswig, Uschi C.T. Gamma, Evan O'Connor, Erik Schnetter The next galactic or nearby extragalactic core-collapse supernova (CCSN) may be detected in gravitational waves (GWs) by the network of advanced-generation GW observatories. We briefly summarize the state of multi-D models of CCSNe and the current understanding of GW emission from core collapse events. We then present new results on the GW signals of neutrino-driven and magnetorotational CCSNe on the basis of fully general-relativistic 3D simulations of core collapse and postbounce evolution. [Preview Abstract] |
Monday, April 15, 2013 12:09PM - 12:21PM |
Q10.00008: Compact binaries in scalar-tensor gravity: Equations of motion and gravitational radiation to high post-Newtonian order Ryan Lang, Saeed Mirshekari, Clifford Will We calculate the equations of motion and gravitational wave emission from binary systems containing neutron stars or black holes in a class of general massless scalar-tensor theories of gravity to high orders in the post-Newtonian (PN) approximation. The strong internal gravity of the bodies is taken into account by letting the mass of each body depend on the value of the scalar field. We present results for the equations of motion through 2.5PN order and show that the equations for binary black holes are observationally identical to those in general relativity. For mixed neutron-star-black-hole systems, the deviations from general relativity depend on a single parameter which is a function of the scalar-tensor coupling constant and the sensitivity of the neutron star's mass to variations in the scalar field. We also report on progress toward determining the gravitational waveform and the energy flux through 2PN order. [Preview Abstract] |
Monday, April 15, 2013 12:21PM - 12:33PM |
Q10.00009: GRB beaming and gravitational-wave observations Hsin-Yu Chen, Daniel Holz Using the observed rate of short-duration gamma-ray bursts (GRBs), it is possible to make predictions for the detectable rate of compact binary coalescences in gravitational-wave detectors. We show that the non-detection of mergers in the existing LIGO/Virgo data constrains the beaming angles and progenitor masses of GRBs. Furthermore, We predict the rate of events in future networks of gravitational-wave observatories, finding that the first detection of a NS--NS binary coalescence associated with the progenitors of short GRBs is likely to happen within the first 16 months of observation, even in the case of a modest network of observatories (e.g., only LIGO-Hanford and LIGO-Livingston) operating at modest sensitivities, and assuming a conservative distribution of beaming angles (e.g. all GRBs beamed with $\theta_j=30^\circ$). We also demonstrate that the detection rate of GRB triggered sources is lower than the rate of untriggered events if $\theta_j \la 30^\circ$, independent of the noise curve, network configuration, and observed GRB rate. Therefore, the first detection in GWs of a binary GRB progenitor is unlikely to be associated with the observation of a GRB. [Preview Abstract] |
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