GCN Circular 2279
Subject
GRB030528(=H2724): X-ray Afterglow Identified in Second Epoch
Date
2003-06-10T12:30:19Z (22 years ago)
From
George Ricker at MIT <grr@space.mit.edu>
GRB030528(=H2724): X-ray Afterglow Identified in Second Epoch
Observations with the Chandra X-ray Observatory
N. Butler, A. Dullighan, P. Ford, G. Ricker, R. Vanderspek (MIT); K.
Hurley , G. Jernigan (U.C.- Berkeley); and D. Lamb (U.Chicago)
on behalf of the Chandra GRB ToO Team and the HETE Science Team
write:
From 9 June 8:14 UT to 9 June 14:19 UT, the Chandra Observatory
targeted the field of the X-ray rich GRB030528, which was localized
by the HETE satellite (Atteia et al. GCN2256; Villasenor et al.
GCN2261). The 20 ksec second epoch (E2) observation with ACIS-S3 was
a follow up to the 25 ksec first epoch (E1) observation performed
with ACIS-S3 on 3 June (Butler et al. GCN 2269).
Of the 4 sources reported in GCN2269 lying within the revised SXC
error region (Villasenor et al. GCN2261) and the 7 sources lying
beyond this error region but inside the ACIS-S3 field-of-view, only
one source declined in brightness with a significance greater than 2
sigma:
# Chandra Name RA DEC E1 Cnts E2 Cnts
1 CXOU J170400.3-223710 17 4 0.31 -22 37 9.99 39 8
Thus, Chandra Source #1 faded by a factor of about 4 between our two
observations (level of significance of approximately 4 sigma; the
implied power law decay index is 2.0 +/- 0.8). Hence, we are quite
confident that Chandra Source #1 is indeed the X-ray afterglow of
GRB030528. Based on the coincidence in position and moderate early
fading in Ks reported by Greiner et al. (GCN 2271) and the faint
lower limit on Ks reported by Bogosavljevic et al. (GCN 2275),
Chandra Source #1 appears to be associated with the NIR candidate
first reported in GCN 2271.
In view of the imminent possibility of a "supernova bump" becoming
visible from GRB030528, we urge continued deep optical and IR
monitoring of Chandra Source #1.
This message may be cited.