Bulletin of the American Physical Society
APS April Meeting 2015
Volume 60, Number 4
Saturday–Tuesday, April 11–14, 2015; Baltimore, Maryland
Session B14: Pulsar Timing |
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Sponsoring Units: DAP Chair: Elizabeth Ferrara, NASA Room: Key 10 |
Saturday, April 11, 2015 10:45AM - 10:57AM |
B14.00001: Intermediate Frequency Gravitational Wave Determination in the 10 micro-Hertz to 20 milli-Hertz Band Using Dense Pulsar Timing Campaigns Timothy Dolch, Michael Lam, Justin Ellis, Shami Chatterjee, James Cordes, Dustin Madison, David Chernoff Dense, continuous pulsar timing observations over a 24-hr period provide a method for probing intermediate gravitational wave (GW) frequencies of 10 micro-Hertz to 20 milli-Hertz. The North American Nanohertz Observatory for Gravitational Waves (NANOGrav), the Parkes Pulsar Timing Array, the European Pulsar Timing Array, and the entire International Pulsar Timing Array all use millisecond pulsar observations to constrain GWs typically at nano-Hz frequencies. In the case of the IPTA's nine-telescope 1713 24-Hour Global Campaign on millisecond pulsar J1713$+$0747 (Dolch et al. 2014), gravitational wave limits in the intermediate frequency regime can be produced. These limits overlap with limits from Cassini Doppler tracking. The negligible change in dispersion measure allows for a white noise model to be used with the timing residuals in order to constrain any contributions from GWs. We show the current status of GW limiting using the 1713 global data. We then discuss the relevant GW sources, and the advantages of using the 1713 global data to limit contributions from such sources. Future campaigns using simultaneous, continuous observations of multiple pulsars will also be discussed. [Preview Abstract] |
Saturday, April 11, 2015 10:57AM - 11:09AM |
B14.00002: Detecting Nanohertz Gravitational Waves with Pulsars Brian Christy The detection of nanohertz gravitational waves will uniquely expand our understanding of galaxy evolution. Source candidates in this frequency band include supermassive black hole binaries (SMBHBs), either as a stochastic background or individual bright sources above this background. Measurement of these signals would provide details to outstanding questions on merger rates and inspiral physics of SMBHB's. This detection is possible with Pulsar Timing Arrays (PTAs) that search for perturbations in pulse arrival times across a collection of precisely timed millisecond pulsars. I will highlight the work of the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), where improvements to instrumentation are substantially increasing sensitivity and current limits already constrain some models for galaxy evolution. [Preview Abstract] |
Saturday, April 11, 2015 11:09AM - 11:21AM |
B14.00003: NANOGrav limits on the isotropic stochastic gravitational wave background from the nine-year data release Justin Ellis, Rutger van Haasteren Pulsar timing arrays (PTAs) offer a unique opportunity to detect low frequency gravitational waves (GWs) in the near future. In this frequency band, the expected source of GWs are Supermassive Black Hole Binaries (SMBHBs) and they will most likely form in an ensemble creating a stochastic GW background with the possibility of a few nearby/massive sources that will be individually resolvable. In this talk we will present preliminary upper limits on the strength of the isotropic stochastic background of gravitational waves using the new 9-year North American NanoHertz Observatory for Gravitational Waves (NANOGrav) data release. We will also discuss the astrophysical implications of these limits and will conclude with some predictions of our future sensitivity to the stochastic GW background. [Preview Abstract] |
Saturday, April 11, 2015 11:21AM - 11:33AM |
B14.00004: Placing limits on anisotropy in the stochastic gravitational wave background with the 9-year NANOGrav data set Chiara Mingarelli Pulsar Timing Arrays are sensitive to gravitational waves in the 1nHz - 100 nHz frequency band. In this very low-frequency regime, we expect to measure a stochastic gravitational wave background generated by the incoherent superposition of gravitational waves from e.g. the cosmic population of supermassive black hole binaries. Previous limits on this stochastic background have assumed an isotropic distribution of the gravitation wave power---here we relax this assumption and look for power in higher order modes using a spherical harmonic decomposition of the GW power on the sky. We discuss the potential and limitations of our method. [Preview Abstract] |
Saturday, April 11, 2015 11:33AM - 11:45AM |
B14.00005: NANOGrav limits on gravitational-wave bursts with memory from the nine-year data release Rutger van Haasteren Highly energetic astrophysical phenomena, like mergers of supermassive black hole binary (SMBHB) systems, are predicted to emit potentially detectable amounts of gravitational radiation. Of specific interest is the non-linear effect known as ``memory'': a permanent and non-oscillatory component of the gravitational waveform created primarily during the most violent moments of the SMBHB inspiral. Pulsar timing arrays offer a unique opportunity to detect such burst with memory (BWM) signals, due to their low-frequency sensitivity. In this talk we will present preliminary upper limits on the event rate of such BWM signals using the new 9-year North American NanoHertz Observatory for Gravitational Waves (NANOGrav) data release. We will also discuss the astrophysical implications of these limits, and projected sensitivity for future releases. [Preview Abstract] |
Saturday, April 11, 2015 11:45AM - 11:57AM |
B14.00006: On the detection of eccentric supermassive black hole binaries with pulsar timing arrays Eliu Huerta, Sean McWilliams, Jonathan Gair, Stephen Taylor It is believed that supermassive black holes (SMBHs) with masses between a million up to a few billion solar masses are ubiquitous in nearby galactic nuclei. Hence, the merger of a pair of galaxies hosting these compact objects may result in the formation of a compact binary that decays to small orbital separations via interactions with its stellar and gaseous environments. Recent studies suggest that these formation channels imply that SMBH binaries may have large orbital eccentricities when they become dominated by gravitational wave emission. In light of these considerations, we present a novel and comprehensive framework that we put at work to carry out an end-to-end analysis of the effect of eccentricity on the amplitude and spectrum of a stochastic, isotropic gravitational wave background from SMBH binaries and single resolvable sources that may be detected with Pulsar Timing Arrays. [Preview Abstract] |
Saturday, April 11, 2015 11:57AM - 12:09PM |
B14.00007: Searching for GW signals from eccentric supermassive black-hole binaries with pulsar-timing arrays Stephen Taylor, Jonathan Gair, Eliu Huerta, Sean McWilliams The mergers of massive galaxies leads to the formation of supermassive black-hole binaries in the common merger remnants. Various mechanisms have been proposed to harden these binaries into the adiabatic GW inspiral regime, from interactions with circumbinary disks to stellar scattering. It may be the case that these mechanisms leave the binary with a residual eccentricity, such that the deviation to the time-of-arrival of pulsar signals induced by the emitted GW passing between the Earth and a pulsar will contain a signature of this eccentricity. Current pulsar-timing search pipelines only probe circular binary systems, but much effort is now being devoted to considering the influence of the binary environment on GW signals. We will detail our efforts in constructing a generalised GW search pipeline to constrain the eccentricity of single systems with arrays of precisely-timed pulsars, which may shed light on the influence of various supermassive black-hole binary hardening mechanisms and illuminate the importance of environmental couplings. [Preview Abstract] |
Saturday, April 11, 2015 12:09PM - 12:21PM |
B14.00008: Using Pulsar Timing observations to understand the formation and evolution of supermassive black hole binaries Neil Cornish, Laura Sampson, Sean McWilliams The astrophysical processes that form and harden supermassive black hole binaries impart distinct features that may be observed in the gravitational-wave spectrum within the sensitive frequency range of Pulsar Timing Arrays (PTA). We investigate how well the various formation and hardening mechanisms can be constrained by applying Bayesian inference to simulated PTA data sets. We find that even without strong priors on the merger rate, any detection of the signal will place interesting constraints on the astrophysical models. Folding in priors on the merger rate allows us to place interesting constraints on the astrophysical models even before a detection is made. [Preview Abstract] |
Saturday, April 11, 2015 12:21PM - 12:33PM |
B14.00009: Timing of Large Magellanic Cloud Pulsars Demi St. John, Josh Ridley We present the timing results of eight recently discovered radio pulsars in the Large Magellanic Cloud (LMC). We went to the Parkes Radio Telescope in Australia and subsequently observed each pulsar monthly, for a total of one year. We will discuss the pulsars' ages, positions, magnetic field strengths, rates of rotation and energy loss. These eight pulsars represent a third of the currently known LMC pulsar population. [Preview Abstract] |
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