[vsnet-grb-info 7715] GRB 090426: VLT spectroscopy

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9269
SUBJECT: GRB 090426: VLT spectroscopy
DATE:    09/04/27 13:43:49 GMT
FROM:    Johan U. Fynbo at U.Copenhagen  <jfynbo at astro.ku.dk>

Christina C. Thoene (INAF/Brera), Daniele Malesani, Johan P. U. Fynbo,
Jens Hjorth (DARK/NBI), Pall Jakobsson (Univ. Iceland), Andrew J. Levan
(Univ. Warwick), Klaas Wiersema, Nial Tanvir (Univ. Leicester), Valerio
D'Elia (INAF/Roma and ASDC), Paul M. Vreeswijk (DARK/NBI), Paolo D'Avanzo
(Univ. Milano-Bicocca & INAF/Brera), Dong Xu (DARK/NBI) report on behalf
of a larger collaboration:

We observed the afterglow of GRB 090426 (Cummings et al., GCN 9254) with
the ESO VLT equipped with the FORS2 spectrograph. Observations were
carried out starting on 2009 Apr 27.048 UT (12.3 hr after the GRB). In the
acquisition image, the afterglow (Cummings et al., GCN 9254) had R ~ 21.65.

Spectra covering the wavelength range 3500-6500 AA were taken, for a total
exposure time of 1 hr. From detection of several absorption features,
including Lyalpha, SiIV 1394, SiIV 1403, CIV 1548/1551, as well as NV
1239/1243, we confirm the redshift z=2.609 derived by Levesque et al.
(GCN 9264).

We note the very low column density (rest EW = 2 AA) of the Lyalpha line,
corresponding to less than 10^19 cm^-2 in HI column density. This
contrasts with the strength of the high-ionization lines.

We acknowledge excellent support from the observing staff at Paranal, in
particular Paul Lynam, Elena Mason, and Jonathan Smoker.