TITLE:   GCN CIRCULAR
NUMBER:  3090
SUBJECT: GRB050309: CONCAM pre-trigger and trigger coincident optical
DATE:    05/03/12 20:21:38 GMT
FROM:    Robert Nemiroff at Michigan Tech.  <nemiroff@mtu.edu>

V. Tilvi, L. Shamir, W. Pereira, D. Cordell, V. Muzzin, M. Merlo & 
R. Nemiroff (Michigan Tech)  report on behalf of the greater Night Sky 
Live Collaboration

The NightSkyLive.net CONCAM2 operating on Mauna Kea has recorded
fisheye images including the location of GRB050309, being sensitive
to the GRB location starting about 28 minutes before Swift trigger.  No bright
optical transient was found consistent with the GRB location on any frame.  
A 170-second exposure including the GRB region was in progress during 
the trigger time and prompt optical emission can be limited as being more 
faint than unfiltered optical CCD magnitude 3.8.  The MK CONCAM image 
at the time of trigger is here: 
http://nightskylive.net/mk/mk050309/mk050309ut104239a.jpg

A table of observation times and approximate limiting magnitudes follows:

Date            From (UT)    To (UT)       m_limit     Remarks
2005-03-09  10:15:03       10:17:53     2.5           28 minutes before trigger
2005-03-09  10:19:00       10:21:50     2.8           Before trigger
2005-03-09  10:22:56       10:24:46     3.0           Before trigger
2005-03-09  10:26:53       10:28:43     3.1           Before trigger
2005-03-09  10:30:47       10:32:37     3.2           Before trigger
2005-03-09  10:38:41       10:40:31     3.5           Before trigger
2005-03-09  10:42:39       10:44:29     3.8           During!  Swift trigger: 10:43:21 UT
2005-03-09  10:46:34       10:48:24     4.0           After trigger
2005-03-09  10:50:32       10:52:22     4.0           After trigger
2005-03-09  10:54:29       10:56:19     4.0           After trigger