Mass fall-back and accretion in the central engine of gamma-ray bursts

By Pawan Kumar, Ramesh Narayan, Jarrett L. Johnson. 2008

174 citations recorded by the source corpus.

We calculate the rate of in-fall of stellar matter on an accretion disc during the collapse of a rapidly rotating massive star and estimate the luminosity of the relativistic jet that results from accretion on to the central black hole. We find that the jet luminosity remains high for about 102 s, at a level comparable to the typical luminosity observed in gamma-ray bursts (GRBs). The luminosity then decreases rapidly with time for about ∼103 s, roughly as ∼t−3; the duration depends on the size and rotation speed of the stellar core. The rapid decrease of the jet power explains the steeply declining X-ray flux observed at the end of most long-duration GRBs. Observations with the Swift satellite show that, following the steep decline, many GRBs exhibit a plateau in the X-ray light curve (XLC) that lasts for about 104 s. We suggest that this puzzling feature is due to continued accretion in the central engine. A plateau in the jet luminosity can arise when the viscosity parameter α is small, ∼10−2 or less. A plateau is also produced by continued fall-back of matter – either from an extended stellar envelope or from material that failed to escape with the supernova ejecta. In a few GRBs, the XLC is observed to drop suddenly at the end of the plateau phase, while in others the XLC declines more slowly as ∼t−1−t−2. These features arise naturally in the accretion model depending on the radius and mean specific angular momentum of the stellar envelope. The total energy in the disc-wind accompanying accretion is found to be about 1052 erg. This is comparable to the energy observed in supernovae associated with GRBs, suggesting that the wind might be the primary agent responsible for the explosion. The accretion model thus provides a coherent explanation for the diverse and puzzling features observed in the early XLC of GRBs. It might be possible to use this model to invert gamma-ray and X-ray observations of GRBs and thereby infer basic properties of the core and envelope of the GRB progenitor star.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/2dcc36904a244ed330f8b0d2cbfe4e40c17ee76d

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. Bing Zhang
2. Pawan Kumar
3. N. Gehrels
4. D. Burrows
5. B. Metzger
6. Xuefeng Wu
7. E. Ramirez-Ruiz
8. E. Berger

In Instrumentation

1. Bing Zhang
2. Pawan Kumar
3. J. Guillochon
4. N. Gehrels
5. E. Ramirez-Ruiz
6. D. Burrows
7. C. Guidorzi
8. Tong Liu

Citations in the corpus

• Neutrino-dominated accretion flows as the central engine of gamma-ray bursts (2017, background): “Wu et al. (2013) presented that a BZ jet launched from the BH hyperaccretion system in the fall-back framework (Kumar et al. 2008a,b) can explain the giant X-ray bump in GRB 121027A. Gao et al. (2016) investigated that the BZ jet and Blandford-Payne (BP, Blandford & Payne 1982) outflow can…”
• The prompt-afterglow connection in gamma-ray bursts: a comprehensive statistical analysis of Swift X-ray light curves (2012, background): “They basically divide into two classes: accretion onto a newly born black hole which directly powers the observed X-ray light-curve (Kumar et al. 2008) or power from a rapidly rotating magnetar (see e.g. Metzger et al. 2011 and references therein).”
• 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, unknown): “Some models (e.g. Kumar et al. 2008) attribute Xray plateaus to the signature of massive star accretion.”
• Unveiling the origin of X-ray flares in gamma-ray bursts (2010, background): “As discussed in the literature (Proga & Begelman 2003; King et al. 2005; Perna et al. 2006; Proga & Zhang 2006; Kumar et al. 2008; Lopez-Camara et al. 2009), there are several mechanisms that could keep the central engine active for a long time or reactivate it in a pseudo-random way.”
• Gamma-Ray Bursts in the Swift Era (2009, background): “…the flow patterns near relativistic objects accreting matter in the hypercritical regime (Di Matteo et al. 2002, Chen and Beloborodov 2007, Proga and Zhang 2006, Perna et al. 2006, Shibata et al. 2007, Kumar et al. 2008), where photons are unable to provide cooling but neutrinos do so efficiently.”
• PS1-10jh: THE DISRUPTION OF A MAIN-SEQUENCE STAR OF NEAR-SOLAR COMPOSITION (2013, background): “While this initial condition is acceptable for fallback calculations onto a newly-formed neutron star in a long GRB (Lee & RamirezRuiz 2006; Kumar et al. 2008; Cannizzo & Gehrels 2009; Lopez-Camara et al. 2009; Milosavljević et al. 2012) and for a compact binary merger (Lee et al. 2004; Metzger et…”
• A complete reference of the analytical synchrotron external shock models of gamma-ray bursts (2013, background): “al engine activities (Troja et al., 2007; Liang et al., 2007; Lyons et al., 2010). A more extreme view interprets all the X-ray afterglow as emission from the central engine (Ghisellini et al., 2007; Kumar et al., 2008b,a). Therefore the external shock model discussed in this review is not relevant ”
• The physics of gamma-ray bursts & relativistic jets (2014, methodology): “On the other hand, a BH based central engine can in principle produce bursts with energy much larger than Kumar et al. (2008b),Lindner et al. (2010).”