[AAVSO-HEN] GRB 090715B: Lick observations

[grb at aavso.org]

The following is a GCN Circular circulated via the AAVSO network.
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TITLE:   GCN CIRCULAR
NUMBER:  9684
SUBJECT: GRB 090715B: Lick observations
DATE:    09/07/17 17:28:04 GMT
FROM:    Daniel Perley at U.C. Berkeley  <dperley at astro.berkeley.edu>

D. A. Perley, J. Choi, A. Morton and M. Ganeshalingam (UC Berkeley) report:

We obtained a series of R-band exposures of the optical transient
associated with GRB 090715B  (GCN 9668, Vetere et al.; GCN 9670, Smith et
al.) at the 1-meter Nickel telescope at Lick Observatory under clear skies
and good seeing.  The transient is detected in individual frames.  We
report the following magnitudes relative to the calibration star of
Malesani et al. (GCN 9671):

t_start(UT)  exp(s)        mag                  t-t0(hr)
06:17:06.10   120    R = 20.23 +/- 0.21           9.23
06:27:36.17   200    R = 20.27 +/- 0.16           9.41
06:31:53.21   200    R = 20.06 +/- 0.14           9.48
06:42:53.80   300    R = 20.48 +/- 0.17           9.66
06:54:57.78   300    R = 20.40 +/- 0.16           9.86
07:01:01.97   300    R = 20.39 +/- 0.20           9.96
07:07:07.30   300    R = 20.24 +/- 0.14           10.07
07:19:01.36   300    R = 20.47 +/- 0.18           10.26
07:32:15.82   300    R = 20.71 +/- 0.23           10.44

A stack of all images gives an average magnitude of R = 20.23 +/- 0.07.