GCN Circular 8345
Subject
GRB 081008: VLT/FORS2 spectroscopy
Event
Date
2008-10-09T03:32:02Z (17 years ago)
From
Paolo D'Avanzo at INAF-OAB <paolo.davanzo@brera.inaf.it>
P. D'Avanzo (INAF-OAB), V. D'Elia (INAF-OAR), S. Covino (INAF-OAB)
report, on behalf of the MISTICI collaboration:
Following the detection of GRB 081008 (Rykoff, GCN 8343; Racusin et al.,
GCN 8344), we triggered observations with the FORS2 camera, mounted at
ESO-VLT. The observations were performed using the 600B grism. We took a
900 s spectrum starting around Oct 09 at 00:20 UT (about 4.5 hours after
the burst) and covering the range 380-620 nm.
The non-detection of Ly-alpha sets an upper limit of z ~ 2 to the GRB
redshift. We detect a double horned absorption feature around lambda
4600 A which we identify as the MgII doublet at 2796-2803 A. This
implies a redshift of the absorber of z = 0.64. We also detect two
absorption features around lambda 4530-4550 A which we identify as FeII
2586 and FeII 2600 A. We possibly interpret this signature as another
absorption system at z = 0.75.
However, at the present stage, the most robust redshift range that we
can set for GRB 081008 is 0.64 < z < 2.
Further analysis is in progress.
We are very grateful for the excellent support of the VLT staff.