GCN Circular 2215
Subject
GRB 030429: Redshift of neighbor galaxy
Event
Date
2003-05-07T16:12:33Z (22 years ago)
From
Johan U. Fynbo at IFA,U of Aarhus <jfynbo@phys.au.dk>
Michael Weidinger, Johan P. U. Fynbo (U. of Aarhus), Jens Hjorth
(U. of Copenhagen), Javier Gorosabel (IAA-CSIC/STScI), Sylvio Klose
(TLS Tautenburg), Nial Tanvir (U. of Hertfordshire) report on behalf of the
GRACE collaboration:
"Further analysis of the VLT spectra of the afterglow of GRB 030429
(GCN 2184) and the neighbor galaxy at a separation of 1.2 arcsec from the
afterglow (GCN 2185, 2196) has led to the following conclusions. Based on
absorption lines due to HI, OI, SiII, and CII we infer a redshift of
z=2.6564+/-0.0008 for GRB 030429. Based on a single, weak emission line in
the spectrum of the neighbor galaxy, which we interpret as [OII], and weak
Calcium H and K absorption we infer a redshift of z=0.841+/-0.001 for the
galaxy. This is consistent with the redshift of an absorption line in the
spectrum of the afterglow if interpreted as MgII. This galaxy is therefore
not the host galaxy of the GRB. In deep images obtained with the VLT/FORS2
on May 5 the afterglow is only barely detected. We do not find any evidence
for a host galaxy at the position of the afterglow to R>25. The separation
between the position of the afterglow and the z=0.841 neighbor galaxy of 1.2
arcsec is comparable to the Einstein radius for a massive galaxy at that
redshift. Gravitational lensing could therefore affect the appearance of
GRB 030429.
We acknowledge excellent support from the Paranal Observatory staff."