On the interpretation of the Fermi-GBM transient observed in coincidence with LIGO gravitational-wave event GW150914

Connaughton, V. et al. (2018) On the interpretation of the Fermi-GBM transient observed in coincidence with LIGO gravitational-wave event GW150914. Astrophysical Journal, 853(1), L9. (doi: 10.3847/2041-8213/aaa4f2)

Abstract

The weak transient detected by the Fermi Gamma-ray Burst Monitor (GBM) 0.4 s after GW150914 has generated much speculation regarding its possible association with the black hole binary merger. Investigation of the GBM data by Connaughton et al. revealed a source location consistent with GW150914 and a spectrum consistent with a weak, short gamma-ray burst. Greiner et al. present an alternative technique for fitting background-limited data in the low-count regime, and call into question the spectral analysis and the significance of the detection of GW150914-GBM presented in Connaughton et al. The spectral analysis of Connaughton et al. is not subject to the limitations of the low-count regime noted by Greiner et al. We find Greiner et al. used an inconsistent source position and did not follow the steps taken in Connaughton et al. to mitigate the statistical shortcomings of their software when analyzing this weak event. We use the approach of Greiner et al. to verify that our original spectral analysis is not biased. The detection significance of GW150914-GBM is established empirically, with a false-alarm rate (FAR) of $\sim {10}^{-4}$ Hz. A post-trials false-alarm probability (FAP) of $2.2\times {10}^{-3}$ ($2.9\sigma $) of this transient being associated with GW150914 is based on the proximity in time to the gravitational-wave event of a transient with that FAR. The FAR and the FAP are unaffected by the spectral analysis that is the focus of Greiner et al.

• Item Type: Articles
• Additional Information: The GBM project is supported by NASA. Support for the German contribution to GBM was provided by the Bundesmi- nisterium für Bildung und Forschung ( BMBF ) via the Deutsches Zentrum für Luft und Raumfahrt ( DLR ) under contract number 50 QV 0301. A.v.K. was supported by the Bundesministeriums für Wirtschaft und Technologie ( BMWi ) through DLR grant 50 OG 1101. J.V. was supported by STFC grant, ST / K005014 / 1. N.C. acknowledges NSF grant PHY- 1505373. P.S. acknowledges NSF grant PHY-1404121.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Veitch, Dr John
• Authors: Connaughton, V., Burns, E., Goldstein, A., Blackburn, L., Briggs, M.S., Christensen, N., Hui, C.M., Kocevski, D., Littenberg, T., McEnery, J.E., Racusin, J., Shawhan, P., Veitch, J., Wilson-Hodge, C.A., Bhat, P.N., Bissaldi, E., Cleveland, W., Giles, M.M., Gibby, M.H., Kienlin, A. v., Kippen, R.M., McBreen, S., Meegan, C.A., Paciesas, W.S., Preece, R.D., Roberts, O.J., Stanbro, M., and Veres, P.
• College/School: College of Science and Engineering > School of Physics and Astronomy
• Research Centre: College of Science and Engineering > School of Physics and Astronomy > Institute for Gravitational Research
• Journal Name: Astrophysical Journal
• Publisher: American Astronomical Society
• ISSN: 0004-637X
• ISSN (Online): 1538-4357
• Published Online: 19 January 2018
• Copyright Holders: Copyright © 2018 The American Astronomical Society
• First Published: First published in Astrophysical Journal 853(1):L9
• Publisher Policy: Reproduced under a Creative Commons License