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GCN Circular 992

Subject
GRB010222 further R-band photometry
Date
2001-02-26T13:48:51Z (23 years ago)
From
Mauro Dolci at Teramo Obs. (OACT), Italy <dolci@astrte.te.astro.it>
Remark: Correction to the magnitude of star "A" and GRB counterpart
candidate in GCN 986


G. Valentini, F. Massi, M. Dolci and E. Di Carlo, 
Osservatorio Astronomico di Teramo (Italy), report:

New R-band observations of the GRB010222 field have been 
carried out with the 512 x 512 CCD camera (4' x 4' FOV) at the focus
of the 0.72-m telescope of the Osservatorio Astronomico di Teramo.
A more accurate photometric calibration has been performed 
both on these new data and on the ones previously reported 
by us (GCN 980). The photometric stability during both nights 
was roughly 0.06 mag.

Final results for the observations reported on Feb 23 (GCN 980) indicate
R=19.63 p/m 0.05 with respect to the R=17 star "A" from Stanek et al.
(GCN 970). However, a calibration made using SA106-1024 from the
Landolt catalogue yields R=17.42 p/m 0.01 for star "A" and R=20.05 p/m 
0.05 for the GRB counterpart candidate (seeing 3.6 arcsec). No colour 
correction was applied. 

The latest set of images was acquired starting on Feb 24.085 UT
and ending on Feb 24.174 UT, for a total exposure time of 2 hours.
The source was no longer detected above a 3-sigma limiting magnitude 
R=21 (seeing about 5 arcsec).

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