GCN Circular 12770
Subject
GRB 111228A: X-shooter spectroscopy
Date
2011-12-29T19:19:59Z (12 years ago)
From
Steve Schulse at U. of Iceland <steve@raunvis.hi.is>
S. Schulze (U Iceland), S. Covino (INAF-OABr), H. Flores (GEPI/Obs. de
Paris), J. P. U. Fynbo (DARK/NBI), B. Milvang-Jensen (DARK/NBI), J.
Sollerman (U Stockholm), D. Xu (WIS) report on behalf of the X-shooter
GRB collaboration:
We observed the afterglow of GRB 111228A (Ukwatta et al. GCN 12737)
with the ESO VLT equipped with the X-shooter spectrograph on 29
December 2011, beginning 07:40 UT (15.93 hr after the GRB). The
afterglow had an R-band brightness of 20.08 mag in a series of five
acquisition images with an exposure time of 30 s each (mid-exposure
time = 15.98 hours). The magnitude is not corrected for Galactic
extinction.
We acquired four spectra with an exposure time of 600 seconds each,
beginning at 07:47 UT. We detect several absorption lines
wave_obs wave_rest Ion redshift
(AA, vac) (AA, vac)
3880.28 2260.78 FeII 0.71634
4023.15 2344.21 FeII 0.71620
4075.26 2374.46 FeII 0.71629
4089.47 2382.77 FeII 0.71627
4422.70 2576.88 MnII 0.71630
4439.44 2586.65 FeII 0.71629
4453.10 2594.50 MnII 0.71636
4462.57 2600.17 FeII 0.71626
4799.05 2796.35 MgII 0.71618
4811.32 2803.53 MgII 0.71616
4896.33 2852.96 MgI 0.71623
6753.24 3934.78 CaK 0.71630
6813.09 3969.59 CaH 0.71632
at a common redshift of z = 0.71627 +/- 0.00002. In addition we detect
[OIII]5007 at z_em = 0.71635, similar to the absorption line redshift.
Our measurements confirm the results by of Cucchiara et al (GCN 12761)
and Palazzi et al (GCN 12763) and are similar to Dittmann et al (GCN
12759) and Xu et al (GCN 12764).
The seeing conditions over the entire campaign were around 0.8 arcsec.
We acknowledge the support of the VLT staff, in particular Claudio
Melo and Christophe Martayan.