Discovery of the nearby long, soft GRB 100316D with an associated supernova

Abstract

We report the Swift discovery of the nearby long, soft gamma-ray burst GRB 100316D, and the subsequent unveiling of its low-redshift host galaxy and associated supernova. We derive the redshift of the event to be z = 0.0591 ± 0.0001 and provide accurate astrometry for the gamma-ray burst (GRB) supernova (SN). We study the extremely unusual prompt emission with time-resolved γ -ray to X-ray spectroscopy and find that the spectrum is best modelled with a thermal component in addition to a synchrotron emission component with a low peak energy. The X-ray light curve has a remarkably shallow decay out to at least 800 s. The host is a bright, blue galaxy with a highly disturbed morphology and we use Gemini-South, Very Large Telescope and Hubble Space Telescope observations to measure some of the basic host galaxy properties. We compare and contrast the X-ray emission and host galaxy of GRB 100316D to a subsample of GRB-SNe. GRB 100316D is unlike the majority of GRB-SNe in its X-ray evolution, but resembles rather GRB 060218, and we find that these two events have remarkably similar high energy prompt emission properties. Comparison of the host galaxies of GRB-SNe demonstrates, however, that there is a great diversity in the environments in which GRB-SNe can be found. GRB 100316D is an important addition to the currently sparse sample of spectroscopically confirmed GRB-SNe, from which a better understanding of long GRB progenitors and the GRB-SN connection can be gleaned.

GRB 080517: a local, low-luminosity gamma-ray burst in a dusty galaxy at z = 0.09

“…The Swift-identified low luminosity events to date -GRB 060218 (Campana et al 2006) and GRB 100316D (Starling et al 2011) -appear to be of extremely long duration (2000 s in the case of GRB 060218) with extremely smooth light curves. They are also very soft events in which the Xray emission exceeds that in the γ−ray (so called X-ray Flashes).…”

“…Only a handful of such low luminosity events have been identified in the past decade, all of which have been relatively local (given the difficulty in observing low luminosity bursts beyond z ∼ 0.1). These include the well studied GRBsupernova pairs GRB 980425/SN 1998bw (Galama et al 1998), GRB 031203/SN 2003lw (Malesani et al 2004;Soderberg et al 2004), GRB 060218/SN 2006aj (Pian et al 2006) and GRB 100316D/SN 2010bh (Starling et al 2011;Cano et al 2011), and the enigmatic GRBs 060505 and 060614, where associated SNe have been ruled out to deep limits, and whose origin remains mysterious (Fynbo et al 2006;Della Valle et al 2006). They may be low luminosity events akin to those above, but where the SNe is absent (e.g.…”

“…However each low redshift host investigated in detail has informed our understanding of the population as a whole and proven to differ from the others (e.g. Watson et al 2011;Starling et al 2011). Low redshift bursts include several which are sub-luminous, such as GRBs 090825 and 031203 (Galama et al 1998;Malesani et al 2004;Soderberg et al 2004), and others such as GRBs 060505 and 060614 that were long bursts without associated supernovae (Fynbo et al 2006;Della Valle et al 2006).…”

GRB Prompt X-ray Emission

“…The existence of an additional blackbody component in the prompt X-ray spectrum of GRB 060218 (Campana et al 2006) and GRB 100316D (Starling et al 2011) has been reported. The blackbody temperature is stable in the range of 0.1-0.2 keV up to several hundreds of seconds after the trigger, and then, decreases to < 0.01 keV.…”

“…While GRB 060218 and GRB 100316D show a duration of several thousands of seconds (Campana et al 2006;Starling et al 2011), SN-GRBs with a duration of a several tens to hundreds of seconds are also common. Although the durations of GRB 060218 and GRB 100316D are exceptionally long, the rest of the sample is well within the duration distribution of typical long GRBs (Figure 2).…”