1 research outputs found
Detection of the high z GRB 080913 and its implications on progenitors and energy extraction mechanisms
Aims: We present multiwavelength observations of one of the most distant
gamma-ray bursts detected so far, GRB 080913. Based on these observations, we
consider whether it could be classified as a short-duration GRB and discuss the
implications for the progenitor nature and energy extraction mechanisms.
Methods: Multiwavelength X-ray, near IR and millimetre observations were made
between 20.7 hours and 16.8 days after the event.
Results: Whereas a very faint afterglow was seen at the 3.5m CAHA telescope
in the nIR, the X-ray afterglow was clearly detected in both Swift and
XMM-Newton observations. An upper limit is reported in the mm range. We have
modeled the data assuming a collimated 3 blast
wave with an energy injection at 0.5 days carrying erg or
approximately 12 times the initial energy of the blast wave. We find that GRB
080913 shares many of the gamma-ray diagnostics with the more recent burst GRB
090423 for being classified as short had they ocurred at low redshift. If the
progenitor were a compact binary merger, it is likely composed by a NS and BH.
The Blandford-Znajek (BZ) mechanism is the preferred one to extract energy from
the central, maximally-rotating BH. Both the magnetic field close to the event
horizon (B) and the BH mass () are restricted within a relatively
narrow range, such that . Similar constraints on the central BH hold for collapsar-like progenitor
systems if the BZ-mechanism works for the system at hand.Comment: 7 pages, 4 figures. Accepted for publication in A&