TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3646
SUBJECT: GRB 050712, Tautenburg optical afterglow observations
DATE:    05/07/19 16:22:14 GMT
FROM:    Andreas Zeh at TLS Tautenburg  <zeh@tls-tautenburg.de>

A. Zeh, D. A. Kann, S. Klose (Thueringer Landessternwarte Tautenburg, Germany),
A. Manning, C. Riddle (Clemson University, SC, USA),

report:

We observed the field of GRB 050712 (Grupe et al. 2005, GCN 3573) with
the Tautenburg 1.34m Schmidt telescope in the R filter at two epochs.

The first set of observations consisted of 10 x 30 second exposures,
mid-exposure time UT 050712.937, i.e. 0.353 days after the GRB. The
second set of observations consisted of 20 x 30 second exposures,
mid-exposure time UT 050713.948, i.e. 1.364 days after the burst.

A comparison of our combined first epoch image with our deeper second
epoch image shows that the potential optical counterpart of the afterglow
(Zeh et al. 2005, GCN 3587) has faded away. Thus, we confirm the earlier
report by Rol et al. (2005, GCN 3575) that the source at coordinates RA,
DEC (J2000) = 5:10:48.1, +64:54:47.6 is the optical counterpart of the
X-ray afterglow (Falcone et al. 2005, GCN 3574; Grupe et al. 2005, GCN 3579).

Assuming R = 15.8 for the USNO-A2.0 star U1500_0409875 at RA, DEC (J2000)
= 05:11:10.51, +64:55:36.0 (Maiorano et al. 2005, GCN 3601), we find the
following magnitudes for the GRB 050712 afterglow:

UT mid		t-t_0 (days)	 mag_Rc

12.937		0.353	          20.7 +/- 0.4
13.948		1.364    	> 21.5

We find that the decay slope alpha is  about 1.2 using the data point by Maiorano 
et al. (2005, GCN 3601).  

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