Columbia University Astronomy and 

University of Michigan 

MDM Observatory GRB Team

2.4m Gunn r
XRT Source #1 Radio Source

GCN Circular #4202: GRB 051105a: MDM Observations
J. P. Halpern, S. Tonnesen, S. Tuttle (Columbia U.), and N. Mirabal
(U. Michigan) report on behalf of the MDM Observatory GRB follow-up team:

"We observed the location of Swift GRB 051105a (Mineo et al., GCN #4188)
using the MDM 2.4m telescope, with a 4.6x4.6 arcminute field centered
on the improved BAT position (Barbier et al., GCN #4194).  A total of
2 and 30 minutes exposure were obtained in the Gunn g and r filters, 
respectively.  The mean epoch of the observations was Nov. 6 02:39 UT,
or 20 hours after the burst.  The following R magnitudes of objects
mentioned in previous GCN circulars were measured, referenced to the
comparison star magnitude R=17.0 used by Piranomonte et al. (GCN #4201):

R.A. (J2000)  Decl. (J2000)      R(mag)          ID             GCN ref
17 41 10.00   +34 55 45.2    21.15 +/- 0.03  inside XRT S1   4195,4196,4201
17 41 10.28   +34 55 41.1    22.50 +/- 0.12  outside XRT S1  4196,4201
17 41 03.28   +34 59 03.6    23.24 +/- 0.22  radio           4199

Positional uncertainties are 0.3" in the USNO B1.0 reference system, except
for the faint object that is, nevertheless, consistent in position with the 
radio source of Frail & Cameron (GCN #4199).  The bright object in the error
circle of XRT S1 is clearly blue in g-r, as well as on the Palomar Sky Survey
plates, and may therefore be an X-ray detected QSO.  Our magnitude of it 
is consistent with that measured by Piranomonte et al. (GCN #4201) 7 hours

Jules Halpern
Nestor Mirabal
Stephanie Tonnesen
Sarah Tuttle
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Last Modified: November 7, 2005