[vsnet-grb-info 4250] GRB 070125: AAVSO optical observations

[GCN Circulars]

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  <aavso at aavso.org>

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.