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GCN Circular 1160

Subject
GRB011121: fainter still
Date
2001-11-25T00:14:55Z (23 years ago)
From
Krzysztof Z. Stanek at CfA <kstanek@cfa.harvard.edu>
K. Z. Stanek (Harvard-Smithsonian CfA) and L. Wyrzykowski (Warsaw
University Observatory) report:


Additional R-band observations of the GRB011121 OT carried out with
the OGLE 1.3m telescope indicate continuing fading behavior of the
afterglow (GCNs 1151, 1152, 1154):

HJD-2450000         UT           R_c       exp
2237.8276     011124 07:47  21.97+-0.07  6x900 sec

The R-band magnitudes are relative to star "A" of Wyrzykowski et
al. (GCN 1150), which we now take to be R=18.2 after correction by 0.8
mag determined by Olsen et al. (GCN 1157) and Brown et al. (GCN 1158).

This measurement might be fairly significantly contaminated by the
possible host galaxy. It was derived with DaoPhot/Allstar PSF-fitting
software (Stetson 1992), which near the OT finds another source
located about 0.8"S and 1.8"E (see deep finding chart and PSF-fitting
residua at http://cfa-www.harvard.edu/cfa/oir/Research/GRB/) with
magnitude R=21.91+-0.07.

We also correct our previous measurements by 0.8 mag:

HJD-2450000         UT           R_c       exp
2235.71890    011122 05:19  19.11+-0.03  200 sec
2235.80322    011122 07:20  19.44+-0.03  200 sec
2235.85176    011122 08:30  19.60+-0.03  600 sec
2236.71036    011123 05:06  21.15+-0.07  3x600 sec

Further, deep observations of the OT are strongly encouraged. We
designate fainter comparison star "C" (see the WWW finding chart),
which by comparison to "A" we measure to be R=20.09+-0.02 (statistical
error only, no color term correction included).


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