Bulletin of the American Physical Society
APS April Meeting 2015
Volume 60, Number 4
Saturday–Tuesday, April 11–14, 2015; Baltimore, Maryland
Session S2: Gravitational Waves and Their Electromagnetic Counterparts |
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Sponsoring Units: DAP Chair: Leo Singer, NASA Room: Holiday 1 |
Monday, April 13, 2015 1:30PM - 1:42PM |
S2.00001: Predictions for Swift Follow-up Observations of Advanced LIGO/Virgo Gravitational Wave Sources Judith Racusin, Phil Evans, Valerie Connaughton The likely detection of gravitational waves associated with the inspiral of neutron star binaries by the upcoming advanced LIGO/Virgo observatories will be complemented by searches for electromagnetic counterparts over large areas of the sky by Swift and other observatories. As short gamma-ray bursts (GRB) are the most likely electromagnetic counterpart candidates to these sources, we can make predictions based upon the last decade of GRB observations by Swift and Fermi. Swift is uniquely capable of accurately localizing new transients rapidly over large areas of the sky in single and tiled pointings, enabling ground-based follow-up. We describe simulations of the detectability of short GRB afterglows by Swift given existing and hypothetical tiling schemes with realistic observing conditions and delays, which guide the optimal observing strategy and improvements provided by coincident detection with observatories such as Fermi-GBM. [Preview Abstract] |
Monday, April 13, 2015 1:42PM - 1:54PM |
S2.00002: The Needle in the 100 deg2 Haystack: From Fermi GRBs to LIGO Discoveries with the Palomar Transient Factory Leo Singer The Fermi satellite has greatly expanded the sample and energy window of gamma-ray bursts (GRBs), but the 10-100 deg$^2$ localizations from the onboard Gamma-ray Burst Monitor (GBM) have posed a formidable obstacle to locating their multiwavelength afterglows with narrow-field instruments. Wide-field, time-domain optical surveys are the key. We present the results of one year of target-of-opportunity searches with the intermediate Palomar Transient Factory (iPTF): the first eight afterglow discoveries based solely on Fermi GBM localizations. Two (GRBs 130702A and 140606B) were at low redshift ($z=$0.145 and 0.384 respectively) and had spectroscopically confirmed broad-line type Ic supernovae. Two are possibly consistent with mildly relativistic shocks breaking out from the progenitor stars, rather than the ultra-relativistic internal shock mechanism that powers standard cosmological bursts. Now that such targeted optical searches are becoming routine, we discuss our preparations to search for optical counterparts of binary neutron star mergers that should soon be detected by Advanced LIGO, scheduled to begin science operations in late 2015. We discuss the future of multimessenger observations with subsequent optical surveys, including the Zwicky Transient Facility (ZTF). [Preview Abstract] |
Monday, April 13, 2015 1:54PM - 2:06PM |
S2.00003: Wide-field X-ray afterglow searches for gravitational wave events Peter Shawhan, Justin Tervala The Advanced LIGO and Virgo gravitational wave (GW) detectors are on track to begin collecting science data soon and to reach full sensitivity by 2019. Low-latency analysis of the GW data will provide triggers for astronomers to seek electromagnetic transient counterparts. Many instruments will contribute to that effort, but instruments with very large fields of view will have a natural advantage for following up the typically large GW error regions. In particular, we consider ISS-Lobster, a proposed NASA mission to be deployed on the International Space Station, which features a focusing imager for soft X-rays with a field of view of over 800 square degrees. Our study using binary neutron star coalescence simulations from Singer et al. shows that a single ISS-Lobster pointing will, on average, cover over 95\% of a LIGO-Virgo 3-detector sky map, while even a 2-detector sky map can be over 85\% covered (on average) by a sequence of four pointings. [Preview Abstract] |
Monday, April 13, 2015 2:06PM - 2:18PM |
S2.00004: A cross-correlation search for intermediate-duration gravitational waves from GRB magnetars Robert Coyne Since the discovery of the afterglow in 1997, the progress made in our understanding of gamma-ray bursts (GRBs) has been spectacular. Yet a direct proof of GRB progenitors is still missing. In the last few years, evidence for a long-lived and sustained central engine in GRBs has mounted. This has called attention to the so-called millisecond-magnetar model, which proposes that a highly magnetized, rapidly-rotating neutron star may exist at the heart of some of these events. The advent of advanced gravitational wave detectors such as LIGO and Virgo may enable us to probe directly, for the first time, the nature of GRB progenitors and their byproducts. In this context, we describe a novel application of a generalized cross-correlation technique optimized for the detection of long-duration gravitational wave signals that may be associated with bar-like deformations of GRB magnetars. The detection of these signals would allow us to answer some of the most intriguing questions on the nature of GRB progenitors, and serve as a starting point for a new class of intermediate-duration gravitational wave searches. [Preview Abstract] |
Monday, April 13, 2015 2:18PM - 2:30PM |
S2.00005: Selecting gravitational wave events for EM follow-up in the advanced detector era Min-A Cho Gravitational wave sources with emissions in the frequency band detectable by ground-based instruments may have electromagnetic (EM) counterparts. The EM counterpart could help confirm the existence of the gravitational wave signature and provide complementary information regarding the source event. However, observable emissions are transient, requiring rapid communication between observing partners and members of the LSC (LIGO Scientific Collaboration) and Virgo in order to be captured. During the past year, we developed and began testing software known as the VOEvent Approval Processor that oversees the selection of events and generation of alerts to be sent to GCN for distribution. This talk will cover how VOEvent Approval Processor has been tested, thus far, and what kind of work is still to be done for its use in the advanced detector era. [Preview Abstract] |
Monday, April 13, 2015 2:30PM - 2:42PM |
S2.00006: Optimizing low latency LIGO-Virgo localization Hsin-Yu Chen, Daniel Holz Fast and effective localization of gravitational wave (GW) events could play a crucial role in identifying possible electromagnetic counterparts, and thereby help usher in an era of GW multi-messenger astronomy. We discuss an algorithm for accurate and very low latency ($\ll1$ second) localization of GW sources using only the time of arrival and signal-to-noise ratio at each detector. The algorithm is independent of distances, masses, and waveform templates of the sources to leading order, and applies to all discrete sources detected by ground-based detector networks. For the two detector configuration (LIGO Hanford+Livingston) expected in late 2015 we find a median 50\% localization of 150 deg$^2$ for binary neutron stars (for SNR threshold of 12), consistent with previous findings. We explore the improvement in localization resulting from high SNR events, finding that the loudest out of the first four events reduces the median sky localization area by a factor of 1.8. We also discuss some strategies to optimize electromagnetic follow-up of GW events. We specifically explore the case of multi-messenger joint detections coming from independent (and possibly highly uncertain) localizations, such as for short gamma-ray bursts observed by Fermi GBM and neutrinos captured by IceCube. [Preview Abstract] |
Monday, April 13, 2015 2:42PM - 2:54PM |
S2.00007: Using Boosting Decision Trees in Gravitational Wave Searches triggered by Gamma-ray Bursts Sarah Zuraw The search for gravitational wave bursts requires the ability to distinguish weak signals from background detector noise. Gravitational wave bursts are characterized by their transient nature, making them particularly difficult to detect as they are similar to non-Gaussian noise fluctuations in the detector. The Boosted Decision Tree method is a powerful machine learning algorithm which uses Multivariate Analysis techniques to explore high-dimensional data sets in order to distinguish between gravitational wave signal and background detector noise. It does so by training with known noise events and simulated gravitational wave events. The method is tested using waveform models and compared with the performance of the standard gravitational wave burst search pipeline for Gamma-ray Bursts. It is shown that the method is able to effectively distinguish between signal and background events under a variety of conditions and over multiple Gamma-ray Burst events. This example demonstrates the usefulness and robustness of the Boosted Decision Tree and Multivariate Analysis techniques as a detection method for gravitational wave bursts. [Preview Abstract] |
Monday, April 13, 2015 2:54PM - 3:06PM |
S2.00008: Search for Gravitational Waves from Nearby Globular Clusters Santiago Caride Although globular clusters in our galaxy are composed primarily of very old stars, there is evidence of young pulsar formation, suggesting that binary formation or collisions take place in these stellar-dense environments. Such events could lead to detectable continuous gravitational radiation from rapidly rotating young neutron stars or from older neutron stars perturbed by collisions with debris. A search for continuous gravitational waves from neutron stars in the nearby globular cluster NGC 6544 using LIGO S6 data, and making use of a new barycentric resampling algorithm that permits deeper searching via a longer coherence time, will be described. [Preview Abstract] |
(Author Not Attending)
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S2.00009: Exploring the Model Dependence of Electromagnetic Signals in Circumbinary Disk Simulations Scott Noble, Manuela Campanelli, Julian Krolik, Bruno Mundim, Hiroyuki Nakano, Yosef Zlochower In this talk, we will present our latest results on 3-d GRMHD simulations of accreting binary black holes during the post-Newtonian inspiral phase of their evolution. The goal of our work is to explore whether these systems provide a unique means to identify and characterize them with electromagnetic observations. We will present results that show how our predicted light curves vary with respect to mass ratio, binary separation, amount of accreting magnetic flux, and the order of accuracy in the post-Newtonian approximation. [Preview Abstract] |
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