TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1699
SUBJECT: GRB 021113:  Evidence for a Dark Optical Afterglow
DATE:    02/11/19 18:54:16 GMT
FROM:    Melissa Nysewander at UNC,Chapel Hill  <mnysewan@astro.unc.edu>

M. Nysewander, D. Reichart (U. North Carolina), and M. Schwartz (Tenagra
Observatories) report on behalf of a larger collaboration:

We observed 100% of the 23 arcmin x 13 arcmin error box, but only 90% of
the revised 26 arcmin x 9 arcmin error box, of GRB 021113 (GCN 1686) with
the 32-inch Tenagra II telescope beginning 2.6 hours (GCN 1687) and 22.3
hours after the burst.  For each epoch, we integrated without filter for
1800 seconds per pointing x two pointings under photometric conditions.
Due to more favorable airmasses, the second epoch observations went deeper.

Calibration images of M67 suggest that unfiltered magnitudes measured with
this CCD best mimic R magnitudes (Henden 2000).  Using the image
subtraction routine ISIS2 (Alard 2000), we find no transients to the
limiting magnitude of our first epoch image, which we measure to be R =
21.5 mag (5 sigma), 22.1 mag (3 sigma), and 23.2 mag (1 sigma) using the
following three USNO-A2.0 stars:

RA (hrs)  DEC (deg)  R (mag)
23.353    40.522     13.8
23.425    40.341     13.9
23.342    40.483     16.7

This is the deepest non-detection of an optical afterglow within four
hours of a burst.

Alard, C., 2000, A&AS 114, 363
Henden, A., 2000, JAAVSO 29, 35