[vsnet-grb-info 8567] GRB 091024: KAIT optical afterglow observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  10075
SUBJECT: GRB 091024: KAIT optical afterglow observations
DATE:    09/10/25 02:54:09 GMT
FROM:    Ryan Chornock at UC Berkeley  <chornock at astro.berkeley.edu>

R. Chornock, W. Li, and A. V. Filippenko (UC Berkeley) report on behalf of the
KAIT GRB team:

The Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory automatically
responded to the Swift BAT trigger for GRB 091024 (Marshall et al., GCN 10062)
with a sequence of observations starting 82 s after the BAT trigger.  The
afterglow is not initially detected.  Our first detection of the optical
afterglow (Mundell et al., GCN 10063) is in a 20 s I band observation starting
at 08:58:45 UT.  The KAIT position is

(J2000) 22:36:59.64  +56:53:24.0

which is consistent the positions reported by Mundell et al. (GCN 10063) and
Henden et al. (GCN 10073).  The optical afterglow is thereafter detected in a
sequence of V, I, and unfiltered images as it rose to a peak at an unfiltered
magnitude of 16.2 (preliminarily calibrated to USNO-B1) at t=404s and then
declined to mag 17.0 at t=988s, similar to the behavior described by Cano et al.
(GCN 10066).  After this time observations ceased due to a pointing limit.