GCN Circular 12009

Eric Broens (Mol, Belgium) and David Boyd (West Challow, Oxfordshire, UK) 
separately reported to the AAVSO International High Energy Network the 
following optical observations of GRB 110503A (GCN Circ. #11991
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 , 
Stamatikos et al.):

E. Broens (VVS WVS, Belgium) reports a detection of GRB 110503A at CR = 
19.6 +/- 0.2 on 2011 May 3.921 UT (JD 2455685.421; midpoint of exposures), 
approximately 4.5 hours after the Swift trigger (GCN Circ. #11991
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 , 
Stamatikos et al.).  Broens obtained 41 frames of 60 seconds exposure in a 
clear filter using a 0.2-meter f7 SCT telescope with SBIG ST-7MXE CCD 
camera.  An ensemble of three nearby SDSS stars were used as comparisons, 
with their R-band magnitudes calculated using the Jester et al. (2009, AJ 
130, 873) relations.  Comparison stars used were: SDSS J085110.53+521301.8 
(R = 17.98) and SDSS J085110.02+521104.6 (R=17.20).  The measured position 
of the GRB was:

 	RA: 08 51 06.3 , Dec: +52 12 26.9

Prior to acquisition of the unfiltered frames, a total of thirty 60-second 
frames (1800s total) were taken with a Cousins R filter centered at 2011 
May 3.895 approximately four hours after the burst.  The filtered 
observations yielded an upper limit of Rc < 18.7.


D. Boyd (West Challow, Oxfordshire, UK) reports V-band optical time series 
of GRB 110503A obtained using a 0.35-m SCT with a Starlight Express 
SXVR-H9 CCD camera.  A total of 150 60-second frames were obtained, and 
these were stacked in groups of 30 to obtain five 1800-second 
integrations.  The burst was detected in all frames.  The resulting 
time-series are as follows:

2011 May 3.89920 UT	V=19.40 +/- 0.04
2011 May 3.92022 UT	V=19.57 +/- 0.04
2011 May 3.94123 UT	V=19.71 +/- 0.04
2011 May 3.96225 UT	V=19.74 +/- 0.05
2011 May 3.98326 UT	V=19.96 +/- 0.05

Magnitudes were obtained using Astrometrica software using UCAC3 for 
positions and photometry; Boyd reports that magnitudes were obtained using 
varying ensembles of between 14 and 19 stars per stacked image. Boyd also 
notes that the coorindates of the GRB on all frames was

 	RA: 08 51 06.19 , Dec: +52 12 27.3 (J2000)


The AAVSO International High Energy Network was made possible through 
grants from the Charles Curry Foundation and NASA.