An optical supernova associated with the X-ray flash XRF 060218

Abstract

Long-duration gamma-ray bursts (GRBs) are associated with type Ic supernovae that are more luminous than average and that eject material at very high velocities. Less-luminous supernovae were not hitherto known to be associated with GRBs, and therefore GRB-supernovae were thought to be rare events. Whether X-ray flashes--analogues of GRBs, but with lower luminosities and fewer gamma-rays--can also be associated with supernovae, and whether they are intrinsically 'weak' events or typical GRBs viewed off the axis of the burst, is unclear. Here we report the optical discovery and follow-up observations of the type Ic supernova SN 2006aj associated with X-ray flash XRF 060218. Supernova 2006aj is intrinsically less luminous than the GRB-supernovae, but more luminous than many supernovae not accompanied by a GRB. The ejecta velocities derived from our spectra are intermediate between these two groups, which is consistent with the weakness of both the GRB output and the supernova radio flux. Our data, combined with radio and X-ray observations, suggest that XRF 060218 is an intrinsically weak and soft event, rather than a classical GRB observed off-axis. This extends the GRB-supernova connection to X-ray flashes and fainter supernovae, implying a common origin. Events such as XRF 060218 are probably more numerous than GRB-supernovae.

Failed Collapsar Jets to Explain Low Luminosity GRB Properties

“…Angular and energetic properties suggest that brief engines (with T inj < T breakout , either due to short T inj or large θ 0 ) represent excellent models to explain the debated llGRBs. In particular, brief engines' jets display two of llGRBs peculiar, and hard to explain, features: 1) an estimated llGRBs rate ~100 times higher than that of GRBs [3,4,5] and, 2) a potentially energetic SN emission ~ 10 51-52 erg [6] (as most of these failed jets' are not well collimated and expands with sub-relativistic velocities). These two features only arise from brief engines.…”

“…llGRBs and their contrast to classical GRBs, present a challenge to the traditional collapsar model. Apart from being several orders of magnitude softer than typical GRBs, llGRBs show: 1) Huge rates, ~100 times than typical GRBs: ~220 Gpc -3 yr -1 [9], ~110 Gpc -3 yr -1 [10], ~260 Gpc -3 yr -1 [11], a rate of llGRBs/GRBs ~ 300 -1000 [12], ~325 Gpc -3 yr -1 [5] and, ~380 Gpc -3 yr -1 [13] (the rate of GRB is ~1 Gpc-3 yr-1). 2) Strong and clear SN connection, in contrast with the typically SN-less GRBs.…”

The First Billion Years project: gamma-ray bursts at z > 5

“…The horizontally dashed black line depicts a metallicity of 1 Z , assuming solar values of Asplund et al 2009. The four coloured marks denote four observed LGRB host galaxies: GRB 130702A (red down triangle; Kelly et al 2013), GRB 060614 (purple down triangle; Della Valle et al 2006), XRF060218 (cyan star; Pian et al 2006;Levesque et al 2010a), and GRB 030329 (green star; Levesque et al 2010a).…”

“…To this end, we collect four of the lowest mass LGRB host galaxies (M * < 10 8 M . ): GRB 130702A (Kelly et al 2013), GRB 060614 (Della Valle et al 2006), XRF060218 (Pian et al 2006;Levesque et al 2010a), and GRB 030329 (Levesque et al 2010a), and plot them in Fig. 5.…”

GRB Prompt X-ray Emission

“…Table 1 shows the list of the spectroscopically identified SN-GRB samples in this work. Three GRBs -030329, 060218, and 100316D (bold fonts in the table) -have secure associations with supernovae since a spectral evolution from a non-thermal power-law to a supernova-like thermal feature is clearly seen in the optical spectroscopic observations (e.g., Stanek et al 2003, Hjorth et al 2003 for GRB 030329; e.g., Pian et al 2006 for GRB 060218; e.g., Chornock et al 2011 for GRB 100316D). …”