Flares in Gamma Ray Bursts: Disc Fragmentation and Evolution

Abstract

Flaring activity following gamma-ray bursts (GRBs), observed in both long and short GRBs, signals a long-term activity of the central engine. However, its production mechanism has remained elusive. Here we develop a quantitative model of the idea proposed by Perna et al. of a disc whose outer regions fragment due to the onset of gravitational instability. The self-gravitating clumps migrate through the disc and begin to evolve viscously when tidal and shearing torques break them apart. Our model consists of two ingredients: theoretical bolometric flare lightcurves whose shape (width, skewness) is largely insensitive to the model parameters, and a spectral correction to match the bandpass of the available observations, that is calibrated using the observed spectra of the flares. This simple model reproduces, with excellent agreement, the empirical statistical properties of the flares as measured by their width-to-arrival time ratio and skewness (ratio between decay and rise time). We present model fits to the observed lightcurves of two well-monitored flares, of GRB 060418 and of GRB 060904B. To the best of our knowledge, this is the first quantitative model able to reproduce the flare lightcurves and explain their global statistical properties.

10 pages, 5 figures, accepted for publication on M.N.R.A.S

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• The Physics of Gamma-Ray Bursts and Relativistic Jets
• X-Ray Flares from Postmerger Millisecond Pulsars
• Neutrino-Cooled Accretion Disks around Spinning Black Hole
• Properties of Gamma-Ray Burst Progenitor Stars
• Fragmentation of Collapsar Disks and the Production of Gravitational Waves
• X-ray flares and the duration of engine activity in gamma-ray bursts
• Instabilities in the time-dependent neutrino disc in Gamma-Ray Bursts
• Compact Binary Progenitors of Short Gamma-Ray Bursts
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• A common stochastic process rules gamma-ray burst prompt emission and X-ray flares
• Self-gravity in neutrino-dominated accretion disks

Cited by in corpus (5)

• Fallback Accretion onto a Newborn Magnetar: short GRBs with Extended Emission
• Late Central Engine Activity in GRB 180205A
• Variability in Short Gamma-ray Bursts: Gravitationally Unstable Tidal Tails
• GRB 111209A/SN 2011kl: Collapse of a supramassive magnetar with r-mode oscillation and fall-back accretion onto a newborn black hole
• Viscous Evolution of Magnetized Clumps: a Source for X-ray Flares in Gamma-ray Bursts