Bulletin of the American Physical Society
APS April Meeting 2012
Volume 57, Number 3
Saturday–Tuesday, March 31–April 3 2012; Atlanta, Georgia
Session Q7: Gravitational Waves: Astrophysics |
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Sponsoring Units: DAP GGR Chair: Peter Shawhan, University of Maryland Room: Embassy D |
Monday, April 2, 2012 10:45AM - 10:57AM |
Q7.00001: LIGO+Virgo Search for Gravitational-Wave Bursts Associated with GRBs Peter Shawhan Gamma-ray bursts are remarkable astrophysical events which emit vast amounts of energy in a short period of time, and likely progenitors are expected to emit gravitational waves (GWs) as well. The long-soft GRBs which make up the majority of the known population are generally believed to come from collapsing massive stars, and there are multiple possible mechanisms for GW emission which could be detectable from a sufficiently close source. Starting with the reported times and sky positions of over 150 GRBs in 2009-2010, we have searched for GW signals in data from the LIGO and Virgo detectors using a coherent ``burst'' search algorithm that can efficiently detect transient GW signals with arbitrary waveforms. I will discuss how the analysis has been optimized and present the latest search results. [Preview Abstract] |
Monday, April 2, 2012 10:57AM - 11:09AM |
Q7.00002: Gamma-Ray burst triggered searches for gravitational wave inspiral signals in LIGO/Virgo data Alexander Dietz Short Gamma Ray Bursts are widely believed to be created from the merger of either two neutron stars or a neutron star and a black hole. As such systems are expected to produce gravitational waves, they are one of the primary targets of gravitational wave detectors, such as LIGO and Virgo. Because the time and the location of such an event is known, the data can be analyzed with a lower threshold compared to untriggered searches. In this talk I will detail the advantages of a triggered search, and present the status of current and past GRB-triggered search in LIGO and Virgo data. Finally, I will give an outlook to detection prospects with advanced detectors which will start taking data around 2015. [Preview Abstract] |
Monday, April 2, 2012 11:09AM - 11:21AM |
Q7.00003: All-sky Search for Gravitational-wave Bursts in the Second Joint LIGO-Virgo Run Amber Stuver The LIGO-Virgo network of gravitational-wave detectors collected data with improved sensitivity in their 2009-2010 science run and, when combined with the previous joint science run in 2005-2007, have produced the most sensitive all-sky burst search to date. Using data from these runs, we describe the search for bursts: short-duration gravitational-wave signals with unknown or poorly modeled waveforms. Such signals may accompany astrophysical events like core-collapse supernovae or the merger phase of coalescing binary compact stars. 207 days of data were collected in 2009-2010 when at least 2 of the 3 LIGO/Virgo detectors were in operation and the data were analyzed in the frequency band of 64-5000 Hz. In this talk, we will discuss the search algorithm used, results, and the astrophysical interpretation when combined with the previous joint search (2005-2007) resulting in 594 days of observation. [Preview Abstract] |
Monday, April 2, 2012 11:21AM - 11:33AM |
Q7.00004: High Precision Gravitational Wave Hubble Diagram with Pulsar Timing Arrays Xihao Deng, Lee Samuel Finn Pulsar Timing Arrays act to detect gravitational waves from supermassive black hole binaries by observing the small, correlated effect the waves have on pulse arrival times at Earth. During the pulse propagation from the pulsar to the Earth, the black hole binaries will evolve driven by gravitational wave emission. By measuring this chirping effect, we can extract the chirp mass and the luminosity distance of the binary. Moreover, with an array of pulsars, we can localize the supermassive black hole binaries and find the host galaxies with corresponding redshifts. With known luminosity distances and corresponding redshifts, we can construct a gravitational Hubble diagram. We have found that by detecting and characterizing 10 to 20 gravitational wave sources with pulsar timing arrays, we can measure Hubble constant and dark energy equation of state within 10\%. [Preview Abstract] |
Monday, April 2, 2012 11:33AM - 11:45AM |
Q7.00005: Pulsar Timing Observations of Black Hole Binaries Neil Cornish, Alberto Sesana Advances in the precision timing of pulse arrival times from a growing network of millisecond pulsars may allow for the detection of nano Hz frequency gravitational waves by the end of the decade. One of the most promising targets for Pulsar Timing Arrays (PTAs) is the background from binary super massive black holes. Traditionally this background has been thought of as being isotropic and stochastic, but more recently it has been realized that the signal will be dominated by a handful of bright sources, leading to a highly anisotropic and deterministic signal. We discuss how this impacts the standard cross-correlation analysis design to detect stochastic signals, and consider alternative detection techniques that are better suited to detecting the expected signal. [Preview Abstract] |
Monday, April 2, 2012 11:45AM - 11:57AM |
Q7.00006: Small Aperture Wide Field Surveys for Gravitational Wave Counterparts Shane L. Larson, Arne A. Henden Multi-messenger astronomy that pairs gravitational wave with electromagnetic observations promises to enable a wide range of scientific endeavors, particularly in cosmology, tests of gravity, and deep probes of stellar-mass binary systems. One of the biggest obstacles to this endeavor is the disparity between the pointing ability of gravitational wave detectors compared to telescopes. Gravitational wave detectors have typical localizations of several square degrees, an area that can encompass hundreds of possible electromagnetic counterparts. In this talk we describe a survey strategy and detection limits using a network of automated small aperture survey instruments. The system is currently being used by the AAVSO to complete the AAVSO Photometric All-Sky Survey (APASS), an all sky multi-band photometric survey down to $m \sim 17$. The network of identical telescopes in this system will be operating on a timescale commensurate with science operations of Advanced LIGO. [Preview Abstract] |
Monday, April 2, 2012 11:57AM - 12:09PM |
Q7.00007: Inferring Core-Collapse Supernova Physics with Gravitational Waves Peter Kalmus Stellar collapse and the subsequent development of a core-collapse supernova explosion emit bursts of gravitational waves (GWs) that might be detected by the advanced generation of laser interferometer gravitational-wave observatories such as advanced LIGO, advanced Virgo, and LCGT. GW bursts from core-collapse supernovae encode information on the intricate multi-dimensional dynamics at work at the core of a dying massive star and may provide direct evidence for the yet uncertain mechanism driving supernovae in massive stars. Recent multi-dimensional simulations of core-collapse supernovae exploding via the neutrino, magnetorotational, and acoustic explosion mechanisms have predicted GW signals which have distinct structure in both the time and frequency domains. Motivated by this, we describe a method for determining the most likely explosion mechanism underlying a hypothetical GW signal, based on Principal Component Analysis and Bayesian model selection. Using simulated advanced LIGO noise and assuming a single detector and linear waveform polarization for simplicity, we demonstrate that our method can correctly identify magnetorotational explosions throughout the Milky Way and explosions driven by the neutrino and acoustic mechanisms to $\sim$2 kpc. [Preview Abstract] |
Monday, April 2, 2012 12:09PM - 12:21PM |
Q7.00008: Detecting and setting upper limits on continuous gravitational waves from unknown spinning neutron stars in binary systems Evan Goetz, Keith Riles An all-sky search for continuous gravitational waves from neutron stars in binary systems is notorious for its computational challenge. The TwoSpect algorithm exploits the periodic orbital modulation of the source waves by searching for patterns in doubly-Fourier transformed data. We present results from simulated data showing the upper-limit sensitivity attainable and successful detections of simulated signals by the TwoSpect search method. [Preview Abstract] |
Monday, April 2, 2012 12:21PM - 12:33PM |
Q7.00009: Distinguishing between merging black hole binaries, with orientation-dependent emission Richard O'Shaughnessy, James Healy, Zachary Meeks, Lionel London, Deirdre Shoemaker Merging black hole binaries emit observationally distinguishable signals in each direction, particularly when symmetry breaking (precession and unequal masses) allow the merger to excite many harmonics. Generally, more (linear) basis functions than angular degrees of freedom are needed to describe each binary's signal, to the accuracy gravitational wave detector noise will permit us to distinguish. This challenge persists even in the simplest possible scenario: low-amplitude, short signals from high-mass binaries ($M>100 M_\odot$). Despite their brevity and thus minimal opportunity to precess in band, we show that merging binaries' detectable signals are \emph{not} universal, with distinctive features not seen in the the emission of nonprecessing binaries. We describe two examples: (a) the precession of a preferred emission orientation through and after merger and (b) the pairwise overlap of signals sent along different directions. We discuss the implications of significant orientation-dependent emission on gravitational wave astrophysics, including source parameter estimation; models of survey selection bias; and construction of hybrids for generic precessing waveforms. [Preview Abstract] |
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