Abstract
Abstract We present a search for prompt gamma-ray counterparts to compact binary coalescence gravitational wave (GW) candidates from Advanced LIGO’s first observing run (O1). As demonstrated by the multimessenger observations of GW170817/GRB 170817A, electromagnetic and GW observations provide complementary information about the astrophysical source, and in the case of weaker candidates, may strengthen the case for an astrophysical origin. Here we investigate low-significance GW candidates from the O1 compact binary coalescence searches using the Fermi Gamma-Ray Burst Monitor (GBM), leveraging its all sky and broad energy coverage. Candidates are ranked and compared to background to measure the significance. Those with false alarm rates (FARs) of less than 10−5 Hz (about one per day, yielding a total of 81 candidates) are used as the search sample for gamma-ray follow-up. No GW candidates were found to be coincident with gamma-ray transients independently identified by blind searches of the GBM data. In addition, GW candidate event times were followed up by a separate targeted search of GBM data. Among the resulting GBM events, the two with the lowest FARs were the gamma-ray transient GW150914-GBM presented in Connaughton et al. and a solar flare in chance coincidence with a GW candidate.
Highlights
The first observing run (O1) of the Advanced LIGO detectors (Aasi et al 2015) marked the dawn of gravitational wave (GW) astronomy with the groundbreaking discovery of merging black holes (BHs; Abbott et al 2016e, 2016g) and Abbott et al (2016b)
Had the lowest p-value of any follow-up event, due to the fact merger, but significant enough that if a gamma-ray transient was found by GammaRay Burst Monitor (GBM) in coincidence, it would support an astrophysical origin of the GW transient
The analysis presented here was not designed to revisit the significance of the GW150914-GBM association; additional observations of binary BHs (BBHs) mergers with GBM will be needed to establish or rule out the astrophysical nature of GW150914GBM
Summary
The first observing run (O1) of the Advanced LIGO detectors (Aasi et al 2015) marked the dawn of gravitational wave (GW) astronomy with the groundbreaking discovery of merging black holes (BHs; Abbott et al 2016e, 2016g) and Abbott et al (2016b). Both pipelines estimate the background distribution of the network statistic in the absence of GWs, which is used to map the network rank of each coincident trigger to the FAR of the search. Virgo Collaborations, and has access to all CBC coincident triggers Because of their different assumptions and implementation details, PyCBC and GstLAL may produce different sets of triggers from the same data. A weak signal can in principle be detected by only one pipeline For this reason, here we combine the triggers produced by both pipelines into a superset of CBC candidates. The candidate list used here was compared to that produced using the final calibration, and the only differences between the two were consistent with random noise fluctuations around the detection threshold of the CBC searches
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