[vsnet-grb-info 298] GRB 020405: HST observations reveal red bump

[GCN Circulars <gcncirc@lheawww.gsfc.nasa.gov>]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1458
SUBJECT: GRB 020405: HST observations reveal red bump
DATE:    02/07/23 07:15:10 GMT
FROM:    Paul Price at RSAA, ANU  <pap@mso.anu.edu.au>

P.A. Price (RSAA, ANU), S.R. Kulkarni, D.W. Fox and J.S. Bloom
(Caltech) report on behalf of the larger Caltech-NRAO-CARA GRB
collaboration:

We observed the afterglow of GRB 020405 (GCN #1326) with HST+WFPC2 at
several epochs spanning 19-31 days after the GRB in F555W, F702W and
F814W, with additional observations approximately two months after the
GRB to remove host contamination.  These observations formed part of
our large Cycle 10 program to search for SNe underlying low redshift
GRBs.

We have performed Novicki-Tonry photometry (see astro-ph/0207187) on
both ground-based and HST imaging.  The resultant light curve,
including data from Bersier et al. (astro-ph/0206465), is at
http://www.mso.anu.edu.au/~pap/grb020405/ .

An excess of flux is evident in the HST images, compared to an
extrapolation of the light-curve from early times.  Based on the red
colour and the time of peak emission, we identify this excess as a SN
associated with GRB 020405.  We have plotted the light-curve of SN
1998bw at z=0.695 (Masetti et al., GCN #1330) and dimmed by 0.5 mag as
a comparison.  This SN appears to be red relative to SN 1998bw, but
this is sensitive to the amount of flux in the afterglow at the final
available HST images.  Further HST observations to measure the host
galaxy and remove this ambiguity are planned for August.

This message may be cited.

VSNET Home Page

Return to Daisaku Nogami

---

vsnet-adm@kusastro.kyoto-u.ac.jp