Bulletin of the American Physical Society
2008 APS April Meeting and HEDP/HEDLA Meeting
Volume 53, Number 5
Friday–Tuesday, April 11–15, 2008; St. Louis, Missouri
Session M10: Gravitational Waves from Neutron Stars and Stochastic Backgrounds |
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Sponsoring Units: GGR DAP Chair: Keith Riles, University of Michigan Room: Hyatt Regency St. Louis Riverfront (formerly Adam's Mark Hotel), St. Louis A |
Sunday, April 13, 2008 3:30PM - 3:42PM |
M10.00001: Displacement Calibration Techniques for the LIGO Detectors Evan Goetz Calibration of the gravitational wave data channels of the Laser Interferometer Gravitational Wave Observatory (LIGO) is critical to determining the sensitivity of the detectors to spacetime perturbations produced by distant astronomical bodies. These detectors are designed to measure relative displacement fluctuations at the level of $10^{-19}$ $\textrm{m}/\sqrt{\textrm{Hz}}$ at 100 Hz. This calibration requires mirror displacement actuation that can be performed without disrupting the servo lock. For LIGO, the actuation for the length sensing and control servo uses voice-coils surrounding magnets glued to the suspended mirrors. This actuation has been calibrated using three techniques: simple Michelson, frequency modulation, and radiation pressure. These methods, which span a wide range of actuation strengths, will be described and compared. [Preview Abstract] |
Sunday, April 13, 2008 3:42PM - 3:54PM |
M10.00002: Beating the spin-down limit on gravitational wave emission from the Crab pulsar Michael Landry Using nine months of data from the fifth science run of the LIGO Scientific Collaboration, we have determined new upper limits on the gravitational wave emission from the Crab pulsar. The result is a stronger constraint than that derived from arguments based on spin down and energy conservation, providing insight into the Crab energy budget. Limits from two searches are presented, one assuming the Crab pulsar emits gravitational radiation at twice the rotation frequency as determined by radio observations, while the other search relaxes this assumption and places an upper limit over a region in frequency and spin-down parameter space centered on twice the rotation frequency. [Preview Abstract] |
Sunday, April 13, 2008 3:54PM - 4:06PM |
M10.00003: Results from the Einstein@Home search of the LIGO S4 data set Bruce Allen We present the results of an all-sky blind search for continuous gravitational waves generated by rapidly-spinning neutron stars. The search was carried out using 510 hours of data from LIGO's fourth science run S4, using computer time donated by the general public. Since Einstein@Home was launched in 2005, more than 100,000 volunteers have contributed over 100 million CPU hours to the project. [Preview Abstract] |
Sunday, April 13, 2008 4:06PM - 4:18PM |
M10.00004: Broadband Search for Continuous-Wave Gravitation Radiation with LIGO Vladimir Dergachev Isolated rotating neutron stars are expected to emit gravitational radiation of nearly constant frequency and amplitude. Searches for such radiation with the LIGO interferometers are underway, using data collected over the past several years. Because the gravitational wave signal amplitudes are thought to be extremely weak, long time integrations must be carried out to detect a signal. This is complicated by the motion of the Earth (daily rotation and orbital motion) which induces substantial modulations of detected frequency and amplitude that are highly dependent on source location. We present an algorithm called PowerFlux, used to account for these modulations, when summing power spectral density estimates incoherently over long time intervals. Current approaches to reconstruction of source parameters, coincidence analysis and outlier followup will also be discussed. We will show results from the application of the PowerFlux detection pipeline to a broadband search in the initial data of the S5 run. [Preview Abstract] |
Sunday, April 13, 2008 4:18PM - 4:30PM |
M10.00005: What can LIGO results say about mountains on pulsars? Benjamin Owen, Richard O'Shaughnessy Neutron stars containing quark matter might have ellipticities large enough to generate periodic gravitational waves detectable in LIGO's recent data. Detection of a large ellipticity would indicate the presence of quark matter, but even upper limits can be interesting. A single upper limit does not constrain the composition of the star because any star may just happen to be very smooth, but a set of upper limits may constrain population statistics and deformation mechanisms. We consider two generic phenomenological models, a static power-law distribution of ellipticities and a dynamical scenario with generic mountain building and mountain shrinking processes. We describe how future LIGO observations, even if they are only upper limits, will constrain these models more than they are already constrained by pulsar spin-downs. [Preview Abstract] |
Sunday, April 13, 2008 4:30PM - 4:42PM |
M10.00006: R-modes in newborn neutron stars: nonlinear development Ruxandra Bondarescu, Saul Teukolsky, Ira Wasserman Rotating neutron stars have modes that are driven unstable by the gravitational radiation reaction, principally the ``R-mode", a L=m=2 Rossby wave. This instability is active when the gravitational driving dominates the internal fluid dissipation of the star. This enables the star to emit a significant fraction of its rotational energy and angular momentum as gravitational waves. It has been suggested that the R-mode instability could explain the relatively low spin frequencies observed in young pulsars. The frequency to which this instability can spin down the star depends on internal neutron star physics such as viscous dissipation, neutrino cooling and strength of magnetic fields. The nonlinear interactions between the R-mode and other near resonant modes in the star play a very important role in determining how this process works, and also illustrates how instabilities can saturate at low amplitudes. My talk will focus on discussing how nonlinear interactions affect the spin evolution of hot young neutron stars in the first few years after formation. [Preview Abstract] |
Sunday, April 13, 2008 4:42PM - 4:54PM |
M10.00007: Search for Stochastic Background of Gravitational Waves with LIGO Vuk Mandic Laser Interferometer Gravitational-wave Observatory (LIGO) has built three multi-km interferometers, designed to detect gravitational waves. One of the possible sources targeted by LIGO is the stochastic background of gravitational waves, whose origin could be cosmological or astrophysical. LIGO has recently completed a year-long science run S5, with all three interferometers at their design sensitivities. We describe the most recent results of the search for the stochastic background of gravitational waves, based on the data from the S5 run. [Preview Abstract] |
Sunday, April 13, 2008 4:54PM - 5:06PM |
M10.00008: Stochastic Background of Gravitational Waves from Cosmological Sources Larry Price, Xavier Siemens Several mechanisms exist for generating a stochastic background of gravitational waves in the period following inflation. These mechanisms are generally ``classical'' in nature, with the gravitational waves being produced from inhomogeneities and not quantum fluctuations. The resulting stochastic background could be accessible to the next generation of gravitational wave detectors. In this talk we'll discuss computational techniques and approximations for computing such a background. Specifically, we'll focus on gravitational waves generated in a simple model of preheating. [Preview Abstract] |
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