Fallback accretion in the aftermath of a compact binary merger

By Stephan Rosswog. 2006

148 citations recorded by the source corpus.

Recent observations of long and short gamma-ray bursts have revealed a puzzling X-ray activity that in some cases continues for hours after the burst. It is difficult to reconcile such time scales with the viscous time scales that an accretion disk can plausibly provide. Here I discuss the accretion activity expected from the material that is launched into eccentric, but gravitationally bound orbits during a compact binary merger coalescence. From a simple analytical model the time scales and accretion luminosities that result from fallback in the aftermath of a compact binary merger are derived. For the considered mass range, double neutron star binaries are relatively homogeneous in their fallback luminosities. Neutron star black hole systems show a larger spread in their fallback behaviour. While the model is too simple to make predictions about the detailed time structure of the fallback, it makes reasonable predictions about the gross properties of the fallback. About one hour after the coalescence the fallback accretion luminosity can still be as large as $\sim 10^{45}$ erg/s, a fraction of which will be transformed into X-rays. Large-scale amplitude variations in the X-ray luminosities can plausibly be caused by gravitational fragmentation, which for the high-eccentricity fallback should occur more easily than in an accretion disk.

Subfields: Astronomy and Astrophysics, Atmospheric Science

View Paper: https://www.semanticscholar.org/paper/a1e875d1282e3a09478852a5f872ae6981053edb

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In Astronomy and Astrophysics

1. Bing Zhang
2. B. Metzger
3. E. Berger
4. E. Quataert
5. Pawan Kumar
6. E. Nakar
7. E. Liang
8. T. Piran

In Atmospheric Science

1. B. Metzger
2. E. Berger
3. T. Piran
4. E. Nakar
5. E. Quataert
6. Bing Zhang
7. W. Fong
8. Stephan Rosswog

Citations in the corpus

• The Binary Neutron Star Event LIGO/Virgo GW170817 160 Days after Merger: Synchrotron Emission across the Electromagnetic Spectrum (2018, background): “The ≈ 2.5M black hole created following the merger will still be accreting fall-back debris from the merger event (e.g. Rosswog 2007; Metzger et al. 2010).”
• DISCERNING THE PHYSICAL ORIGINS OF COSMOLOGICAL GAMMA-RAY BURSTS BASED ON MULTIPLE OBSERVATIONAL CRITERIA: THE CASES OF z = 6.7 GRB 080913, z = 8.2 GRB 090423, AND SOME SHORT/HARD GRBs (2009, background): “The merger models therefore must be modified to account for this extended emission (Rosswog 2007).”
• Short-Duration Gamma-Ray Bursts (2013, background): “However, fall-back accretion may also explain the plateaus (Rosswog 2007).”
• Signatures of magnetar central engines in short GRB light curves (2013, background): “There have been studies of fallback accretion, in which the NS is shredded and parts (6 10% of the original disk mass) are flung c© 000 RAS into highly eccentric orbits which accrete onto the centralengine at late times giving flares in the X-ray lightcurve (Rosswog 2007).”
• The multimessenger picture of compact object encounters: binary mergers versus dynamical collisions (2012, methodology): “In this context, it was pointed out that compact binary mergers possess in addition a much longer time-scale due to nearly unbound material that will finally fall back to the central remnant (Faber et al. 2006; Lee & Ramirez-Ruiz 2007; Rosswog 2007a).”
• Short-duration gamma-ray bursts with extended emission from protomagnetar spin-down (2007, background): “For BH-NS mergers, the fall-back of matter ejected into highly eccentric orbits during the NS’s tidal disruption may be sufficient to power the EE (Rosswog 2007), but whether the regular delay between the prompt and EE phases, and the large variation in the flux of each, can be reproduced remains…”
• Time-dependent models of accretion discs formed from compact object mergers (2008, background): “…2005; although this explanation may have difficulty reproducing the observed timescales, Piro & Pfahl 2007), differential rotation in a post-merger millisecond pulsar (Dai et al. 2006), and an infalling tidal tail of material stripped from the disrupted NS (Lee & Ramirez-Ruiz 2007; Rosswog 2007).”
• GRB 080503: IMPLICATIONS OF A NAKED SHORT GAMMA-RAY BURST DOMINATED BY EXTENDED EMISSION (2008, background): “…that the luminosity of the extended emission can exceed that of the ini- 13 tial spike by factors of 30 or more is problematic for a merger, in which the majority of the accretion disk is expected to accrete within a viscous timescale — not more than a few seconds (Rosswog 2007; Lee et al. 2004).”
• Multiband light curves of tidal disruption events (2010, background): “Similar processesalso occur for lower mass objects, such as in compact binary systems, hosting i) a stellar mass black hole and a white dwarf (Rosswog et al. 2008); or ii) two white dwarfs (Rosswog 2007; Rossi & Begelman 2009).”
• THE FORMATION OF ECCENTRIC COMPACT BINARY INSPIRALS AND THE ROLE OF GRAVITATIONAL WAVE EMISSION IN BINARY–SINGLE STELLAR ENCOUNTERS (2013, background): “…astronomy offers tantalizing prospects for probing the nature of compact objects, their binary assembly, evolution, and eventual merger (Rosswog 2007b,a; Bloom et al. 2009; Lee et al. 2010; Rosswog et al. 2012; Faber & Rasio 2012; Metzger & Berger 2012; Lehner et al. 2012; Kelley et…”