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GCN Circular 2681

Subject

GRB 040827: Detection of NIR afterglow

Date

2004-08-28T02:32:35Z (20 years ago)

From

Edo Berger at Carnegie Obs <eberger@ociw.edu>

M. Gladders and E. Berger (Carnegie Observatories) report:
                                          
"We imaged a portion of the 2.5-arcmin error circle of GRB 040827 (GCN
#2672Not found
 
 
), centered on the XMM-Newton X-ray source (GCN #2678Not found
 
 
), with the
PANIC instrument on the Magellan Baade 6.5-m Telescope.  A total of 36
minutes were obtained in the Ks-band under good weather conditions with a
seeing of about 0.55".  Within the 10-arcsec XMM error circle we find two
sources with a magnitude of Ks~19.8+/-0.2 mag (XMM-1) and Ks~19.4+/-0.15
mag (XMM-2) compared to 2MASS.  The positions of the two source are
(J2000):
        RA=  15:17:01.43
        DEC= -16:08:22.7        (XMM-1)
and
        RA=  15:17:01.35
        DEC= -16:08:28.6        (XMM-2)
 
Source XMM-1 coincides with the I-band source reported by Berger, Thompson
and Krzeminski (GCN #2680Not found
 
 
), while source XMM-2 appears to be extended.  
We therefore conclude that XMM-1 is the likely optical/NIR afterglow of
GRB 040827.  A comparison of the Ks- and I-band magnitudes indicate a
spectral index beta~-0.5 typical of GRB afterglows."