GCN Circular 1375
Subject
GRB020405: VLT observations of the OT environment
Date
2002-04-18T14:18:16Z (23 years ago)
From
Nicola Masetti at ITeSRE,CNR,Bologna <masetti@tesre.bo.cnr.it>
N. Masetti, E. Palazzi (IASF/CNR, Bologna), E. Maiorano, A. Simoncelli
(U. Bologna), E. Pian (INAF, OA Trieste), A. Castro-Tirado (IAA-CSIC,
Granada), A. Fruchter (STScI, Baltimore), J. Greiner (MPE Garching
and AI Potsdam), J. Hjorth (U. Copenhagen), L. Kaper, E. van den Heuvel
(U. Amsterdam), R. Cabanac, A. Kaufer (ESO), on behalf of the GRACE
Collaboration, report:
"We have obtained an R-band image (2 x 3 minutes integration) of GRB020405
from VLT-UT3 (Melipal) plus FORS1 on 2002 Apr. 15.244 under a seeing of
0.65 arcsec.
We find that the OT is located within a complex environment composed of
at least four extended objects, one of which is underlying the OT and
showing a bright knot (possibly a star-forming region, or alternatively
the host nucleus) ~1 arcsec south of the OT itself.
Also, the presumed host galaxy indicated by Hjorth et al. (GCN #1329)
and located ~2 arcsec southwest of the OT seems not to be the actual host
but a galaxy which is likely interacting with it.
Indeed, a spectrum of this galaxy taken with Melipal+FORS1 on
2002 April 7.310 shows that it is at the same redshift of the OT
(GCNs #1330, #1340).
This finding strengthens the suggestion that GRBs are sometimes associated
with interacting galaxies possibly displaying substantial star formation,
as seen e.g. for GRB001007 (Castro Ceron et al. 2002, A&A, in press
[astro-ph/0110049]).
No suggestion of a break in the light curve (see GCN #1369) is apparent
up to ~10 days after the GRB.
However, in the VLT image reported above, the OT brightness is already
substantially contamined by the host emission. For this reason it would
be quite difficult to see any future possible break in the OT light
curve with ground-based observations.
A close-up of the VLT R-band field around the OT can be found at:
http://tonno.tesre.bo.cnr.it/~masetti/grb020405.html
This message can be cited.".