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GCN Circular 12470

GRB 111020A: Gemini-South additional observations and limit on an optical afterglow
2011-10-22T02:47:44Z (13 years ago)
Wen-fai Fong at CFA <>
W. Fong and E. Berger (Harvard) report:

"We re-imaged the field of GRB 111020A (GCN 12640) with GMOS on the
Gemini-South telescope on 2011 October 22.01 UT (mid-time of 1.7 days
post-burst, and 23.1 hours after our initial observations; GCN 12467).  We
obtained 11x180s exposures in i-band in 0.73" seeing.

We still detect the two faint sources S1 and S2 from our previous GMOS
observation (GCN 12467), and neither source shows evidence for fading.
Digital image subtraction of the two epochs using the ISIS package reveals
no residuals inside or near the XRT error circle.  We therefore place a
limit on the optical afterglow of i~25 mag at 17.7 hours after the burst."
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