[vsnet-grb-info 1772] GRB 050709: optical afterglow candidate

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3612
SUBJECT: GRB 050709: optical afterglow candidate
DATE:    05/07/14 22:04:37 GMT
FROM:    Paul Price at IfA,UH  <price at ifa.hawaii.edu>

P. A. Price (IfA, Hawaii), B. L. Jensen, U. G. Jargensen, J. Hjorth, J.
P. U. Fynbo, D. Watson, J. M. Castro Ceron, K. Pedersen, H. Pedersen,
and J. Sollerman (DARK Cosmology Centre, Niels Bohr Institute) report:

We have performed PSF-matched image subtraction on the images acquired
by Jensen et al. (GCN #3589).  The images were obtained from the Danish
1.54m+DFOSC at La Silla on 2005 July 11.3 and 12.3 UT.

PSF-matched image subtraction using the Pan-STARRS Optimal Image
Subtraction (POI Sub) code reveals a residual, in the sense that the
source fades between the first and the second epochs.  The position of
the variable source corresponds to the source identified by Jensen et
al. (GCN #3589) on the edge of a nearby galaxy (z=0.16; Price, Roth &
Fox, GCN #3605) as consistent with the Chandra source (Fox et al., GCN
#3585).  This detection of optical variability increases the likelihood
that this source is the afterglow of the short/hard GRB 050709.

A figure showing the subtraction is available at
http://www.ifa.hawaii.edu/~price/grb050709candidate.jpg

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