INTEGRAL Upper Limits on Gamma-Ray Emission Associated with the Gravitational Wave Event GW150914
Hanlon, L.; Mereghetti, S.; von Kienlin, A.; Ubertini, P.; Ferrigno, C.; Bozzo, E.; Bazzano, A.; Laurent, P.; Natalucci, L.; Diehl, R.; Savchenko, V.; Kuulkers, E.; Lebrun, F.; Roques, J. P.; Courvoisier, T. J. -L.; Brandt, S.; Weidenspointner, G.
France, Switzerland, Italy, Denmark, Germany, Ireland, Spain
Abstract
Using observations of the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL), we place upper limits on the gamma-ray and hard X-ray prompt emission associated with the gravitational wave event GW150914, which was discovered by the LIGO/Virgo Collaboration. The omnidirectional view of the INTEGRAL/SPI-ACS has allowed us to constrain the fraction of energy emitted in the hard X-ray electromagnetic component for the full high-probability sky region of LIGO triggers. Our upper limits on the hard X-ray fluence at the time of the event range from {F}γ =2× {10}-8 erg cm-2 to {F}γ ={10}-6 erg cm-2 in the 75 keV-2 MeV energy range for typical spectral models. Our results constrain the ratio of the energy promptly released in gamma-rays in the direction of the observer to the gravitational wave energy E {}γ / E {}{GW}\lt {10}-6. We discuss the implication of gamma-ray limits for the characteristics of the gravitational wave source, based on the available predictions for prompt electromagnetic emission.