2008/08/31 by Elena M. Rossi, Mitchell C. Begelman · 44 citations
Earth and Planetary Sciences · Physics and Astronomy · #Accretion (finance) #Accretion disc #Binary number #Black hole (networking) #Earth Systems and Cosmic Evolution #Gamma-ray bursts and supernovae #Gravitational wave #Neutron star #Opacity #Plasma #Pulsars and Gravitational Waves Research #astro-ph
paper · pdf · doi:10.1111/j.1365-2966.2008.14139.x
published in Monthly Notices of the Royal Astronomical Society 392(4), 1451-1455 (Oxford University Press) · 5 pages, 1 figure, MNRAS in press after minor revisions
arxiv created 2008/11/16 · openalex publication_date 2008/12/22 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
When double neutron star or neutron star–black hole binaries merge, the final remnant may comprise a central solar-mass black hole surrounded by a ∼0.01–0.1 M⊙ torus. The subsequent evolution of this disc may be responsible for short γ-ray bursts (SGRBs). A comparable amount of mass is ejected into eccentric orbits and will eventually fallback to the merger site after ∼0.01 s. In this paper, we investigate analytically the fate of the fallback matter, which may provide a luminous signal long after the disc is exhausted. We find that matter in the eccentric tail returns at a super-Eddington rate and eventually (≳0.1 s) is unable to cool via neutrino emission and accrete all the way to the black hole. Therefore, contrary to previous claims, our analysis suggests that fallback matter is not an efficient source of late-time accretion power and unlikely to cause the late-flaring activity observed in SGRB afterglows. The fallback matter rather forms a radiation-driven wind or a bound atmosphere. In both the cases, the emitting plasma is very opaque and photons are released with a degraded energy in the X-ray band. We therefore suggest that compact binary mergers could be followed by an ‘X-ray renaissance’, as late as several days to weeks after the merger. This might be observed by the next generation of X-ray detectors.