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[vsnet-grb-info 568] GRB 021112: Afterglow or Variable Star?
TITLE: GCN GRB OBSERVATION REPORT
NUMBER: 1701
SUBJECT: GRB 021112: Afterglow or Variable Star?
DATE: 02/11/20 19:05:03 GMT
FROM: Melissa Nysewander at UNC,Chapel Hill <mnysewan@astro.unc.edu>
M. Nysewander, D. Reichart (U. North Carolina), A. Henden (USRA/USNO), G.
G. Williams (MMTO/SAO), and M. Schwartz (Tenagra Observatories) report on
behalf of a larger collaboration:
We observed fields containing the candidate afterglow of GRB 021112 (GCN
1696) 4 days after the burst in BVRcIc, 6 days after the burst in Rc, and 7
days after the burst in H. Using the field calibration of Henden (GCN
1697) and 2MASS, we report preliminary photometry:
Date Time Filter Magnitude Telescope
Oct 16.2 4.0 days V 21.48 +- 0.08 90-inch Bok
Oct 16.3 4.1 days B > 22.6 (3 sigma) 90-inch Bok
Oct 16.3 4.1 days Ic 19.39 +- 0.09 32-inch Tenagra II
Oct 16.3 4.1 days Rc 20.87 +- 0.07 32-inch Tenagra II
Oct 18.3 6.1 days Rc 20.84 +- 0.06 1.0-meter USNO
Oct 19.2 7.0 days H * 17.44 +- 0.17 1.55-meter USNO
* 2MASS field not available. Calibration based on 2MASS Quicklook image
and consequently caution is warranted. However, candidate is strongly
detected: Internal errors are ~0.01 mag.
Using the images of Strolger et al. (GCNs 1684, 1696), kindly provided by
J. E. Rhoads, we have placed their photometry on the same photometric
system:
Date Time Filter Magnitude Telescope
Oct 12.3 3.2 hours Rc 20.86 +- 0.05 4-meter Mayall
Oct 13.2 1.0 days Rc 20.31 +- 0.06 4-meter Mayall
Although we do not find evidence for variability in the R-band light curve
outside of the discovery epoch, which could be explained by an afterglow in
a R = 20.86 +- 0.03 galaxy, 1.0 arcsec seeing on Oct. 19th shows the
candidate to have a star-like profile (this image is available upon
request).
This, in addition to the candidate's location outside of HETE's 90% error
box and an otherwise rarely seen brightening a day after the burst, suggest
that the candidate is probably a variable star of some type instead of an
afterglow in a bright, compact galaxy.
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