[vsnet-grb-info 6124] GRB 080520: VLT redshift

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  7757
SUBJECT: GRB 080520: VLT redshift
DATE:    08/05/21 11:38:56 GMT
FROM:    Pall Jakobsson at U Hertfordshire  <P.Jakobsson at herts.ac.uk>

Pall Jakobsson (U. Hertfordshire), Johan P. U. Fynbo,
Daniele Malesani, Jens Hjorth and Bo Milvang-Jensen
(DARK, NBI) report on behalf of a larger collaboration:

Using FORS2 on the Very Large Telescope, we have obtained
3*30 min spectra (grism 300V) of the optical afterglow of
GRB 080520 (Grupe et al., GCN 7753). The acquisition image
shows it to have R = 23.0 +/- 0.5 on May 21.235 (7.3 hours
post burst).

A firm upper limit of z < 2.4 can be placed on the redshift
of GRB 080520 from the lack of Ly-alpha forest lines in the
spectrum of the afterglow. This is consistent with the GROND
observations (Rossi et al., GCN 7756).

The combined spectrum shows an emission line, presumably
corresponding to [O II] 3727 at z = 1.545. At this redshift
we also find the Mg II doublet (2796,2803) and Mg I (2852).

We thank the Paranal staff for excellent support, especially
Yuri Beletsky and Patricia Guajardo.