[vsnet-grb-info 43] GRB011212, Optical Observations

[GCN Circulars <gcncirc@lheawww.gsfc.nasa.gov>]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1216
SUBJECT: GRB011212, Optical Observations
DATE:    02/01/07 23:31:17 GMT
FROM:    Fredrick J. Vrba at USNO  <fjv@nofs.navy.mil>

F.J. Vrba (USNO), A.A. Henden (USNO/USRA), and B. Canzian (USNO)
report on behalf of the USNO GRB team:

We used the USNO 1.3-m telescope to obtain Ic-band imaging at two
epochs of a 20(N-S)x40(E-W) arcmin field that is approximately centered 
on the joint HETE/RXTE_ASM error box for GRB011212 (GCN 1194+alert).
The registration covers approximately 95% of the error box, with only
4 arcmin in declination of its southern tip missed. Observations
on both nights consisted of six 10 minute integrations using a Site
2Kx4K CCD and were calibrated photometrically using several stars
in the field from Henden (GCN 1198). Observations were obtained on
UT 2001 Dec 13.294-13.351 (1.125-1.182 days after the burst) with
the combined frames reaching a limiting magnitude of Ic < 21.6 and 
on UT 2001 Dec 14.207-14.281 (2.038-2.112 days after the burst) 
reaching a limiting magnitude of Ic < 21.9 (due to better seeing than 
on the previous night). The combined frames from each night were
blinked and the entire 20x40 arcmin FOV was searched with the result 
that no fading objects were found. 

The GRB position (at l ~ 172 deg, b ~ -6 deg) is a region of
moderately high Galactic extinction, with E(B-V) ranging from 0.71 to
0.84 at the center and corners of the error box based on the dust maps
of Schlegel et al. (ApJ, 500, 525). Assuming a normal extinction law,
this implies a range of A_I of about 1.4-1.6 mag. Our observations
thus place an apparent upper limit of Ic > 21.6 or an extinction-corrected 
limit of Ic > 20.0-20.2 at 1.125-1.182 days after the burst for an
Ic-band counterpart to GRB011212.

These results may be cited.

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