GCN Circular 10073

A. Henden (AAVSO), J. Gross (SRO), B. Denny (DC-3), D. Terrell (SwRI), and
W. Cooney (SRO) report:

We obtained photometry of the GRB091024 afterglow reported by Mundell et
al. (GCN 10063
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 ) using the Sonoita Research Observatory (SRO) 35cm telescope
in southern Arizona, utilizing an automatic VOevent trigger.  The Rc-band
exposures began about 9 minutes after the burst and continued for approximately
one hour.  Ten Rc-band, nine V-band, and one Ic-band exposures were acquired.

Photometry, assuming that USNO-B1.0 1468-0448363 (RA: 22:36:44.11 ,
Dec: +56:52:42.6) has the following magnitudes: V=13.46, R=12.93, I=12.71

UT(mid)   delT   exp   mag     err  filter
09.1122    642   180  17.177  0.030   Rc
09.1667    839   180  17.510  0.037   Rc
09.2192   1028   180  17.827  0.049   Rc
09.2722   1218   180  17.993  0.044   Rc
09.3247   1407   180  18.136  0.056   Rc
09.4123   1723   300  18.008  0.046   Rc
09.5000   2038   300  17.764  0.045   Rc
09.5859   2348   300  17.737  0.033   Rc
09.6717   2657   300  17.665  0.037   Rc
09.7575   2965   300  17.776  0.045   Rc
09.8609   3338   300  19.029  0.111   V
09.9486   3653   300  19.267  0.120   V
10.0348   3964   300  19.290  0.132   V
10.1206   4273   300  19.320  0.126   V
10.2064   4581   300  19.237  0.091   V
10.2923   4891   300  19.345  0.151   V
10.4642   5510   300  19.163  0.107   V
10.5500   5818   300  19.293  0.123   V
10.6359   6128   300  19.350  0.163   V
10.8439   6877   180  17.550  0.074   Ic


Where delT is the time in seconds from the burst (Marshall et al., GCN
10062
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 ), and the exposure is in seconds.

Astrometry from the Rc frames, using UCAC3, yields a precise position of
22:36:59.68 +56:53:23.3 J2000 (+/- 100mas).  A full BVRcIc calibration
is in the Sonoita queue and will be released when photometric conditions
permit.

The AAVSO thanks the Curry Foundation for its support of the AAVSO
International High Energy Network.