GCN Circular 518

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

We have acquired UBVRcIc all-sky photometry for the field
of GRB991216 with the USNOFS 1.0-m telescope on four
photometric nights, but with some nights having
poor seeing.  This field is reddened, with
a mean color (B-V) ~ 1.2.  Because of this, many of
the fainter sources do not have U or B magnitudes.  We have
therefore created two files on our anonymous ftp site:
ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb991216.dat
ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb991216f.dat
where the first file contains multicolor observations, and
the second file contains a smaller set of fainter stars
surrounding the OT position, but with only R magnitudes
listed.  In particular, the R magnitudes we obtain for
stars A and B of Jha (GCN 476
Not found
 
 
) and the comparison
star of Henden (GCN 463
Not found
 
 
) agree with those obtained by
Dolan, et. al. (GCN 486
Not found
 
 
) within the quoted errors.
The astrometry in these files is based on linear plate
solutions with respect to USNO-A2.0.  The internal errors
are less than 100mas.

We also observed this field with the USNO IRCAM on the
1.55-m telescope on a single photometric night to obtain
JHK photometry for 6 stars near the OT position. Observations
were obtained of 11 standard stars to put the measures on the
CIT photometric system. The errors reflect uncertainties in the
in the extinction and color transformations. The data were
reduced independently in K and H magnitudes and J-H and H-K
colors:

RA (J2000)     DEC           K          H          J-H       H-K
77.375279   11.288480  11.77+/-.03 11.92+/-.03 0.69+/-.03 0.19+/-.03  
77.374150   11.285729  12.48   .03 12.62   .03 0.70   .04 0.19   .03
77.392377   11.290707  14.00   .04 14.19   .03 0.82   .04 0.27   .03 
77.399284   11.290875  14.68   .08 14.85   .10 0.50   .10 0.25   .10
77.377129   11.297201  14.61   .07 14.65   .05 0.61   .04 0.11   .05