TITLE: GCN CIRCULAR NUMBER: 6048 SUBJECT: GRB 070125: AAVSO optical observations DATE: 07/01/28 14:07:02 GMT FROM: AAVSO GRB Network at AAVSO D.T. Durig (Cordell-Lorenz Observatory, University of the South) and B. Gary (Hereford Arizona Observatory) report on behalf of the AAVSO International High Energy Network on optical observations of GRB070125 (GCN #6024, Hurley et al.): D.T. Durig reports the following unfiltered (CR) magnitudes: 2007 Jan 27, 04:02:58 UT: 19.4 +/- 0.2 (CR) 2007 Jan 27, 05:08:10 UT: 19.7 +/- 0.2 (CR) 2007 Jan 27, 06:13:17 UT: 19.9 +/- 0.2 (CR) 2007 Jan 27, 07:27:28 UT: 20.0 +/- 0.2 (CR) B. Gary reports the following unfiltered magnitudes: 2007 Jan 27, 06:22:12 UT: 19.58 +/- 0.12 (clear) 2007 Jan 28, 05:36:00 UT: 20.20 +/- 0.24 (clear) Details of these observations are available from the AAVSO at ftp://ftp.aavso.org/grb , and full details of these observations are available at the following URLs: Durig: http://www.aavso.org/pipermail/aavso-hen/2007-January/006934.html Gary: http://www.aavso.org/pipermail/aavso-hen/2007-January/006937.html ----------------------------- Observer: D. T. Durig, D. S. Hardage, N. M. Haymond, (CLW01) Report: Afterglow is very faintly visible in single 120 sec images with SNR 2.5 to 3.5. Very obvious in stacks of 10, 15 and 30 frames. Position of 07 51 17.74 +31 09 04.1. Stacks of 30 frames gives SNR of 13 with magnitude falling from 19.6 to 19.7 to 19.9 to 20.0 in each hour long stack. We lost about 12 minutes in the last stack because we lost our guide star, so intervals are slightly different. GIF image posted to http://arthur.sewanee.edu/obsv/view.php Observer: B. Gary Report: One day later (2007.01.28, UT = 5.60) CV = 20.20 +/- 0.24. CV for Jan 27 & 28 UT asssume B-V = +0.3. All SE errors are orthogonal sum of stochastic and estimated systematic.