[vsnet-grb-info 4946] GRB 070724: optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6666
SUBJECT: GRB 070724: optical observations
DATE:    07/07/25 13:21:12 GMT
FROM:    Silvia Piranomonte at OAR  <piranomonte at mporzio.astro.it>

S. Covino (INAF/OABr), S. Piranomonte (INAF/OAR), S.D. Vergani (DIAS and
DCU), P. D'Avanzo (INAF-OABr), L. Stella (INAF/OAR), report on behalf of
the MISTICI collaboration:

We observed the afterglow of GRB 070724 (Ziaeepour et al., GCN 6654)
with the ESO-VLT equipped with FORS2. Starting on 2007 Jul 25.3735 UT
(22.1 hr after the trigger), we acquired 10 minutes of imaging in the I
band. Inside the XRT error circle (Page & Ziaeepour, GCN 6659), we
detect both objects reported by Bloom (GCN 6658) and Cenko et al. (GCN
6664).

When compared with the photometry reported by Cenko et al. (GCN 6664),
none of the objects seems to have faded. The faintest object is
pointlike (seeing of 0.7").

We also took two 10-min spectra with VLT+FORS2. Based on detection of [OII] 3727
Hbeta and [OIII] 4959,5007, we confirm the redshift z=0.457 proposed by Cucchiara
et al. (GCN 6665).

We thank Brad Cenko for very useful discussion.

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