On the possible gamma-ray burst–gravitational wave association in GW150914

Abstract

Data from the Fermi Gamma-ray Burst Monitor satellite observatory suggested that the recently discovered gravitational wave source, a pair of two coalescing black holes, was related to a gamma-ray burst. The observed high-energy electromagnetic radiation (above 50 keV) originated from a weak transient source and lasted for about 1 second. Its localization is consistent with the direction to GW150914. We speculate about the possible scenario for the formation of a gamma-ray burst accompanied by the gravitational-wave signal. Our model invokes a tight binary system consisting of a massive star and a black hole which leads to the triggering of a collapse of the star's nucleus, the formation of a second black hole, and finally to the binary black hole merger. For the most-likely configuration of the binary spin vectors with respect to the orbital angular momentum in the GW150914 event, the recoil speed (kick velocity) acquired by the final black hole through gravitational wave emission is of the order of a few hundred km/s and this might be sufficient to get it closer to the envelope of surrounding material and capture a small fraction of matter from the remnant of the host star. The gamma-ray burst is produced by the accretion of this remnant matter onto the final black hole. The moderate spin of the final black hole suggests that the gamma-ray burst jet is powered by weak neutrino emission rather than the Blandford-Znajek mechanism, and hence explains the low power available for the observed GRB signal.

Analysis of Sub-threshold Short Gamma-Ray Bursts in Fermi GBM Data

“…These range from the dissipation of the Poynting flux energy through the merger of two charged black holes (Fraschetti 2018;Liebling & Palenzuela 2016;Zhang 2016); super-Eddington accretion through a BBH merger within an AGN disk (Bartos et al 2017;Stone et al 2017), or a BBH system with a long-lived disk of ambient material (Murase et al 2016;Perna et al 2016). Other theories include the triggered collapse of a massive star due to its black hole companion (Janiuk et al 2017), and the fragmentation of the stellar core of a massive star (Loeb 2016; although see Dai et al 2017 andFedrow et al 2017). Lyutikov (2016) has argued that the physical properties necessary to create GW150914-GBM are highly implausible, although Khan et al (2018) surveyed different models of disks around merging BBHs using magnetohydrodynamic simulations and shows that such systems could produce an EM counterpart consistent with the properties of GW150914-GBM.…”

Black Hole Accretion in Gamma Ray Bursts

“…More recently, accretion flows are described by fully relativistic MHD computations (e.g., [10,11] ). This method has also been applied recently to describe the central engine of a putative gamma ray burst which could be associated with the event GW150914 [12]. Here we report on this work, and in addition, we also present new results on the nucleosynthesis of heavy elements in the accretion flow in this engine.…”

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

“…Although the potential for EM counterparts to BBH mergers has not been well established in the literature, recent development spurred by the GBM report of a candidate counterpart to GW150914 (e.g., Fraschetti 2016;Loeb 2016;Janiuk et al 2017) suggests that mechanisms may exist. The connection between BNS (or NS-BH) mergers and sGRBs is much stronger than that of BBH mergers (Metzger & Berger 2012;Nissanke et al 2013), supported by extensive observational evidence (host galaxy observations and offsets, environmental densities inferred from GRB afterglow modeling, observational rates; Troja et al 2008;Fong et al 2015), and consistency with numerical modeling (jet production, magnetic fields; Rosswog 2005;Rezzolla et al 2011).…”

“…The excitement of the watershed LIGO discovery has precipitated numerous merger models with EM emission components, ranging from sGRBs to optical and radio transients (e.g., Murase et al 2016) and even luminous neutrino sources (e.g., Moharana et al 2016;Janiuk et al 2017). This discussion is restricted to an incomplete selection of counterpart models, with a view to defining key observational elements that modelers should address in future studies.…”

“…Note that the candidate GBM counterpart was not detected by the INTEGRAL SPI-ACS (Anti-Coincidence Shield; Savchenko et al 2016), and there is debate regarding the nature of the GBM signal (Greiner et al 2016). Since the potential discovery was announced, innovative ideas have emerged to explain an observational signature that possibly resembles a weak sGRB from a BBH (e.g., Fraschetti 2016;Loeb 2016;Perna et al 2016, andJaniuk et al 2017); see also Lyutikov (2016) for significant constraints on such models. Binary neutron star (BNS) or neutron starblack hole (NS-BH) mergers are the most likely progenitors of sGRBs (Eichler et al 1989;Narayan et al 1992; Lee &Ramirez-Ruiz 2007, andNakar 2007), and therefore they are the most similar object class for comparison to Fermi observations of BBH mergers.…”