Gamma-Ray Bursts in Circumstellar Shells: A Possible Explanation for Flares

Abstract

It is now generally accepted that long-duration gamma-ray bursts (GRBs) are due to the collapse of massive rotating stars. The precise collapse process itself, however, is not yet fully understood. Strong winds, outbursts, and intense ionizing UV radiation from single stars or strongly interacting binaries are expected to destroy the molecular cloud cores that give birth to them and create highly complex circumburst environments for the explosion. Such environments might imprint features on GRB light curves that uniquely identify the nature of the progenitor and its collapse. We have performed numerical simulations of realistic environments for a variety of long-duration GRB progenitors with ZEUS-MP and have developed an analytical method for calculating GRB light curves in these profiles. Though a full, three-dimensional, relativistic magnetohydrodynamical computational model is required to precisely describe the light curve from a GRB in complex environments, our method can provide a qualitative understanding of these phenomena. We find that, in the context of the standard afterglow model, massive shells around GRBs produce strong signatures in their light curves, and that this can distinguish them from those occurring in uniform media or steady winds. These features can constrain the mass of the shell and the properties of the wind before and after the ejection. Moreover, the interaction of the GRB with the circumburst shell is seen to produce features that are consistent with observed X-ray flares that are often attributed to delayed energy injection by the central engine. Our algorithm for computing light curves is also applicable to GRBs in a variety of environments such as those in high-redshift cosmological halos or protogalaxies, both of which will soon be targets of future surveys such as the Joint Astrophysics Nascent Satellite or Lobster.

Finding the First Cosmic Explosions. I. Pair-Instability Supernovae

“…Although x-rays from these events can trigger Swift or its successors such as the Joint Astrophysics Nascent Universe Satellite (JANUS, Mészáros & Rees 2010;Roming 2008;Burrows et al 2010), their afterglows ) are more likely to be detected in all-sky radio surveys by the Extended Very-Large Array (eVLA), eMERLIN and the Square Kilometer Array (SKA) (de Souza et al 2011b) due to their low event rates. We are now evaluating detection limits for Pop III GRBs in a variety of circumstellar environments (Mesler et al 2012(Mesler et al , 2013.…”

Finding the First Cosmic Explosions. Ii. Core-Collapse Supernovae

“…Although X-rays from these events may be detected by Swift or its successors such as the Joint Astrophysics Nascent Universe Satellite (JANUS; Mészáros & Rees 2010;Roming 2008;Burrows et al 2010), their afterglows ) might also be detected in all-sky radio surveys by the Extended Very Large Array (eVLA), eMERLIN, and the Square Kilometer Array (SKA; de Souza et al 2011). We are now studying detection limits for Pop III GRBs in a variety of circumstellar environments (Mesler et al 2012(Mesler et al , 2013.…”

How the First Stars Regulated Star Formation. II. Enrichment by Nearby Supernovae

“…This transition in turn regulates the luminosities, spectra and star formation rates of primeval galaxies (Greif et al 2008;Johnson et al 2009;Greif et al 2010;Jeon et al 2012;Pawlik et al 2011;Wise et al 2012;Pawlik et al 2013;O'Shea et al 2015), the demographics and rates of supermassive black hole formation (Tanaka & Haiman 2009;Alvarez et al 2009;Park & Ricotti 2011;Park & Ricotti 2012;Volonteri 2012;Agarwal et al 2012;Park & Ricotti 2013;Choi et al 2013;Latif et al 2013a,b;Schleicher et al 2013;Johnson et al 2014;Smidt et al 2017;Woods et al 2017;Haemmerlé et al 2017), and the onset of cosmological reionization (Whalen et al 2004;Kitayama et al 2004;Alvarez et al 2006;Abel et al 2007). This transition also influences the rate at which primordial SNe may be detected in future surveys Kasen et al 2011;Mesler et al 2012;Whalen et al 2013f,a,b;de Souza et al 2013;Whalen et al 2013c,d,e;Mesler et al 2014;Whalen et al 2014a,b;Smidt et al 2014;de Souza et al 2014;Chen et al 2014a,b,c;Smidt et al 2015;Magg et al 2016) and the number of low-mass Pop III stars and second-generation stars expected in Galactic archaeological searches…”