Searching for electromagnetic counterpart of LIGO gravitational waves in theFermiGBM data with ADWO

Abstract

Aims. The Fermi collaboration identified a possible electromagnetic counterpart of the gravitational wave event of September 14, 2015. Our goal is to provide an unsupervised data analysis algorithm to identify similar events in Fermi's Gamma-ray Burst Monitor CTTE data stream. Methods. We are looking for signals that are typically weak. Therefore, they can only be found by a careful analysis of count rates of all detectors and energy channels simultaneously. Our Automatized Detector Weight Optimization (ADWO) method consists of a search for the signal, and a test of its significance. Results. We developed ADWO, a virtual detector analysis tool for multi-channel multi-detector signals, and performed successful searches for short transients in the data-streams. We have identified GRB150522B, as well as possible electromagnetic candidates of the transients GW150914 and LVT151012. Conclusions. ADWO is an independently developed, unsupervised data analysis tool that only relies on the raw data of the Fermi satellite. It can therefore provide a strong, independent test to any electromagnetic signal accompanying future gravitational wave observations.

Searching the Gamma-Ray Sky for Counterparts to Gravitational Wave Sources: Fermi Gamma-Ray Burst Monitor and Large Area Telescope Observations of Lvt151012 and Gw151226

“…We find no evidence for the counterpart reported by Bagoly et al (2016) in their search of the GBM data around LVT151012. Our search method combines signals in the 14 GBM detectors in a way that tests for the likelihood of a source from any sky position.…”

“…By using the detector responses rather than examining just the raw count rates above background, we can find weak sources that are consistent with an astrophysical source while rejecting fluctuations of similar magnitude in counts space. That we do not find the candidate counterpart reported in Bagoly et al (2016) suggests that either the relative rates among detectors or the distribution of counts in energy for their event are not indicative of a physical source from a single sky position. Indeed, Bagoly et al (2016) state that they do not use the response information to weight the relative signals when combining detector information, instead weighting the contributions of each detector and energy channel according to signal-to-noise ratio above the background count rates, without consideration as to whether the weighted spectrum is physical or the detector weights are consistent with an arrival direction from a single position.…”

Spectral classification and variation of Fermi GRBs

“…It has two instruments, the Large Area Telescope (LAT), and the Gamma-ray Burst Monitor (GBM). The GBM is used to study gamma-ray bursts; the data received by its 14 detectors (12 NaI and 2 BGO) are collected by a central Data Processing Unit (DPU) [17]. The database from the Fermi GBM detectors, the FERMIGBRST 1 catalog [18,19] contains more than 2000 GRBs with several parameters such as position, durations, flux, fluences and spectral properties.…”

Testing the Isotropic Universe Using the Gamma-Ray Burst Data of Fermi/GBM

“…Specifically we employed the FER-MIGBRST -Fermi GBM Burst Catalog 2 (Gruber et al 2014;von Kienlin et al 2014;Narayana Bhat et al 2016), which is being constantly updated. While methods for measuring GRB properties more precisely has been suggested (Szécsi et al 2013), and alternative data mining strategies has been developed to identify nontriggered events (Bagoly et al 2016), this is still one of the most complete burst catalog to date. A sample containing 1594 GRBs with the first and the last event detected on 14 Jul 2008 and on 15 Apr 2015, respec-tively, is used.…”