GRB 170817A-GW170817-AT 2017gfo and the observations of NS-NS, NS-WD and WD-WD mergers

Abstract

The LIGO-Virgo Collaboration has announced the detection of GW170817 and has associated it with GRB 170817A. These signals have been followed after 11 hours by the optical and infrared emission of AT 2017gfo. The origin of this complex phenomenon has been attributed to a neutron star-neutron star (NS-NS) merger. In order to probe this association we confront our current understanding of the gravitational waves and associated electromagnetic radiation with four observed GRBs originating in binaries composed of different combinations NSs and white dwarfs (WDs). We consider 1) GRB 090510 the prototype of NS-NS merger leading to a black hole (BH); 2) GRB 130603B the prototype of a NS-NS merger leading to massive NS (MNS) with an associated kilonova; 3) GRB 060614 the prototype of a NS-WD merger leading to a MNS with an associated kilonova candidate; 4) GRB 170817A the prototype of a WD-WD merger leading to massive WD with an associated AT 2017gfo-like emission. None of these systems support the above mentioned association. The clear association between GRB 170817A and AT 2017gfo has led to introduce a new model based on on a new subfamily of GRBs originating from WD-WD mergers. We show how this novel model is in agreement with the exceptional observations in the optical, infrared, X-and gamma-rays of GRB 170817A-AT 2017gfo.

Time evolution of rotating and magnetized white dwarf stars

“…Soft gamma-repeaters and anomalous X-ray pulsars appear to be an exciting possibility to confirm such a hypothesis (Malheiro et al 2012;Boshkayev et al 2013a;Rueda et al 2013;Lobato et al 2016). The massive, highly magnetized WDs produced by WD binary mergers, recently introduced as a new class of low-luminosity gammaray bursts (Rueda et al 2018(Rueda et al , 2019 would be another interesting case.…”

Induced Gravitational Collapse, Binary-Driven Hypernovae, Long Gramma-ray Bursts and Their Connection with Short Gamma-ray Bursts

“…We now give a brief description of all the GRB subclasses identified. In [49] we have renominated the GRB subclasses introduced in [45] and in [50,51], and inserted them into two groups: binary-driven hypernovae (BdHNe) and compact-object binary mergers. Below we report both the old and the new names to facilitate the reader when consulting our works prior to [49].…”

“…In that case the transient is powered by the energy release from the decay of r-process heavy nuclei processed in the merger ejecta [60][61][62][63]. FB-KN stands for fallback-powered kilonova [50,51]: a WD-WD merger can emit an infrared-optical transient, peaking at ∼5 day post-merger, with the ejecta powered by accretion of fallback matter onto the newborn WD formed in the merger. The density rate of the GRB subclasses BdHN III (HN) and BM IV (FB-KN) have not yet been estimated.…”

“…Up to 2017 we had introduced seven GRB subclasses summarized in Table 1. In addition, we have recently introduced in [50,51] the possibility of a further GRB subclass produced by WD-WD mergers. We now give a brief description of all the GRB subclasses identified.…”

The jet structure and the intrinsic luminosity function of short gamma-ray bursts

“…However, somewhat abnormally, the prompt luminosity of GRB 170817A of ∼ 10 47 erg s −1 is actually hundreds of times lower than the lowest luminosity of the normal cosmological (i.e., z 0.1) SGRBs (Abbott et al 2017b;. This promoted some people to consider that GRB 170817A could belong to a new SGRB population (e.g., Rueda et al 2018). As one possibility, it was suggested that GRB 170817A could be produced by a mildly-relativistic, radially structured, and isotropic outflow (e.g., a cocoon powered by a chocked jet; Kasliwal et al 2017;Mooley et al 2018;Nakar & Piran 2018), rather than by a traditional relativistic jet (e.g, Paczynski 1986; Eichler et al 1989;Meszaros & Rees 1992;Narayan et al 1992).…”