Bulletin of the American Physical Society
APS April Meeting 2018
Volume 63, Number 4
Saturday–Tuesday, April 14–17, 2018; Columbus, Ohio
Session H14: Gravitational Waves: Searches and Detected Signals |
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Sponsoring Units: DGRAV Chair: Peter Shawhan, University of Maryland, College Park Room: A226 |
Sunday, April 15, 2018 10:45AM - 10:57AM |
H14.00001: Status of the LISA Data Challenges John Baker Following the restart of the Laser Interferometer Space Antenna (LISA) mission project by the European Space Agency last year there is new urgency to establish a solid foundation for LISA science analysis. This has motivated a new community effort to conduct a series of LISA Data Challenges. Anticipated sources include massive black hole mergers, stellar origin black holes, extreme mass ratio inspirals, stochastic backgrounds and millions of galactic binaries all superposed in the LISA data stream. The LDC effort will tackle a series of increasingly rigorous challenges aimed to develop source models, data analysis algorithms and software resources needed to demonstrate readiness and to realize LISA's science objectives in support of mission formulation studies already underway. The first data sets, beginning with elementary source examples, are now available. Future challenges will add rigor, incorporating, for example, realistic data features including gaps and glitches, etc. Researchers are invited to join us in demonstrating techniques for characterizing the first round events and in the challenges to come. [Preview Abstract] |
Sunday, April 15, 2018 10:57AM - 11:09AM |
H14.00002: The all-sky search for unmodeled gravitational-wave transients with Advanced LIGO-Virgo Ryan Lynch Gravitational-wave astronomy has been enlightened by recent detections of the merger of compact stellar remnants by the advanced LIGO-Virgo detectors. In addition to these mergers, future detections by LIGO-Virgo may include the core-collapse of massive stars, transient neutron star phenomena, cosmic string cusps and other as yet unknown sources. Searches for this latter category of transients often make minimal assumptions regarding their exact waveform morphologies, and are thus referred to as unmodeled searches. The network of the Advanced LIGO-Virgo gravitational-wave detectors completed in August 2017 its second observing run ("O2"). In this talk, we present the status of the O2 searches for unmodeled gravitational-wave transients and plans for the upcoming third observing run ("O3") expected to commence in late 2018. [Preview Abstract] |
Sunday, April 15, 2018 11:09AM - 11:21AM |
H14.00003: Search for Gravitational Waves Associated with Gamma-Ray Bursts During the Second Advanced LIGO Observing Run Robert Coyne The joint-observation of an astrophysical event with both gravitational wave (GW) and electromagnetic (EM) observatories has long been a dream of the astronomical community. With the recent detection of binary neutron star (BNS) merger GW170817 by LIGO/Virgo and its associated gamma-ray burst (GRB) by EM observatories that dream is now reality, entering us into a new age of multi-messenger astronomy. But this event marks only the beginning. While GW170817 represents the "smoking gun" for BNS mergers being the progenitor of at least some (short) GRBs, there remain many questions about the nature of these energetic cosmic events. Here we report on efforts to perform targeted GW analysis of GRBs reported by EM observatories during LIGO's second observing run (O2). In addition to detailed followup of GW170817, we discuss the analysis of sub-threshold GRBs that follow naturally from the GW170817 search. We also analyze nearly 250 other GRBs, searching both for unmodeled GW bursts as well as BNS singals coincident with their EM counterparts. This "archival" search benefits from improved sensitivity over rapid "online" searches performed throughout O2 thanks to finalized data calibration. Beyond preliminary results, we also look forward to improvements for LIGO's third observing run. [Preview Abstract] |
Sunday, April 15, 2018 11:21AM - 11:33AM |
H14.00004: Past, present and future of the LIGO-Virgo gravitational-wave early alerting system E Katsavounidis The first two observing runs in 2015-2017 of the advanced LIGO-Virgo gravitational-wave detectors have ushered a new era in multi-messenger astronomy. The discoveries of compact binary systems and the ability to provide early alerts of their detection by LIGO-Virgo have enabled breakthrough observations across the electromagnetic spectrum and neutrinos. The LIGO-Virgo resuming of observations in late 2018 will signal the beginning of making such early alerts for gravitational-wave detections open to the scientific community and the broader public. We will summarize the operations of such early alerting system during the first two runs of the instruments and present the highlights and challenges we face as we transition to an open, public alert system expected to be in place later in 2018. [Preview Abstract] |
Sunday, April 15, 2018 11:33AM - 11:45AM |
H14.00005: Wide parameter searches for continuous waves with Advanced LIGO Vladimir Dergachev Continuous waves from non-axisymmetric neutron stars are orders of magnitude weaker than transient events from black hole and neutron star collisions. As continuous waves from galactic sources are expected to persist across an observing run the searches are carried out by integrating months of collected data. This greatly increases sensitivity, with a corresponding increase in analysis complexity. All-sky and spotlight searches are designed to cover large parameter spaces, trading off potential sensitivity of a single-target search for greater chance of detection. We will present latest analysis results and discuss algorithms that make large-scale analysis practical and efficient. [Preview Abstract] |
Sunday, April 15, 2018 11:45AM - 11:57AM |
H14.00006: Pulsar-timing-array searches for stochastic gravitational waves vs Solar-System Ephemerides Michele Vallisneri The premiere source for pulsar-timing arrays such as the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) is the stochastic background from a population of inspiraling supermassive--black-hole binaries. The analysis of pulsar-timing data relies on the accurate knowledge of the motion of the Earth around the Solar-System barycenter. Current pulsar-timing-array datasets have become so sensitive that gravitational-wave--background upper limits and detection statistics are biased by the errors in current Solar-System ephemerides. NANOGrav developed a novel approach to marginalize search results over uncertainties in Earth's orbit, producing the first pulsar-timing-array constraints that are robust against ephemeris error. I describe this work and comment on expectations for the accuracy of future ephemerides, as well as prospects for pulsar-timing data to augment direct observations in determining the orbits of Solar-System bodies. [Preview Abstract] |
Sunday, April 15, 2018 11:57AM - 12:09PM |
H14.00007: Evolution of limits on the gravitational-wave stochastic background using the NANOGrav 11-year dataset Jeffrey Hazboun The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) is a collaboration of scientists who monitor an array of millisecond pulsars as a galactic-scale gravitational-wave observatory. The timing precision of these pulsars is reaching a level ($\sim 100$ ns) where one can measure the expected (Hellings and Downs) correlations between pulsars to look for the signature of ultra-low-frequency gravitational waves. Since the maximum power of the stochastic background of gravitational waves from super-massive black hole binaries is thought to be at frequencies smaller than 1/yr, the signal is expected to grow slowly as we are able to observe for longer durations and as we add more pulsars to our array. With the most recent data release, we have undertaken an investigation into the evolution of our signal by slicing the dataset in time and running our statistical analyses on its subsets. We will demonstrate how this technique can be used to assess various characteristics of our pulsar timing array, including the effect of losing one of our telescopes, how removal of our best-timed pulsar affects our limits, and expectations about the evolution of our signal in the future. The investigation into unexpected features of the evolution will also be discussed. [Preview Abstract] |
Sunday, April 15, 2018 12:09PM - 12:21PM |
H14.00008: Limits on Gravitational Waves from Individual Supermassive Black Hole Binaries from the NANOGrav 9-year and 11-year Data Sets Sarah Vigeland Pulsar timing arrays (PTAs) are sensitive to gravitational waves with frequencies between about 1 - 100 nHz. Sources in this regime include supermassive black hole binaries, which are believed to form as a result of galaxy mergers. We have searched the 9-year and 11-year data sets from the North American Nanohertz Observatory for Gravitational Wave Observatory (NANOGrav) for gravitational waves from individual supermassive black hole binaries. We present upper limits on the strain amplitude from individual supermassive black hole binaries, as well as lower limits on the luminosity distance to individual sources. We also show how our sensitivity varies with sky location due to the distribution of pulsars in our array. [Preview Abstract] |
Sunday, April 15, 2018 12:21PM - 12:33PM |
H14.00009: Limits on gravitational wave memory from the NANOGrav 11-year data set Paul Baker The merger of binary supermassive black holes (SMBH) can produce permanent changes in the spacetime metric referred to as gravitational wave (GW) memory. While the GW bursts associated with merger are outside of the typical sensitive frequency band for pulsar timing arrays (PTA), the memory effect can be detected by them. We present PTA limits on GW memory from merging SMBH using NANOGrav's the 11-year data set. We discuss the sensitivity of the NANOGrav array to GW memory as a function of the time and sky position of the merger. [Preview Abstract] |
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