TITLE:   GCN CIRCULAR
NUMBER:  6328
SUBJECT: GRB 070419A: Early Super-LOTIS Observations
DATE:    07/04/20 04:03:14 GMT
FROM:    Grant Williams at Steward Observatory  <ggwilli@mmto.org>

G. G. Williams (MMTO) and P. A. Milne (Steward Observatory), on behalf of 
the Super-LOTIS Collaboration, report:

The robotic 0.6-m Super-LOTIS telescope began observing the error box of 
GRB 070419A (Swift Trigger 276205, Stamatikos et al. GCN 6302) at 
10:01:08.1 UT, 102 seconds after the trigger.  Our initial observations 
include 5 x 10s exposures, 5 x 20s exposures, and 30 x 60s exposures, all 
in the R-band.

We detect the afterglow reported by Chornock et al. (GCN 6304) in our 
third (and subsequent) 60 second exposure which began at 10:07:01.8 UT, 
456 seconds after the trigger.  We do not detect the afterglow in early 
single exposures or early summed exposures. This is evidently related to 
the brightening reported by Cenko et al. & Wren et al. (GCN 6306 & 6324).

Using the USNO-B star at RA=12:10:57.57, Dec=+39:55:40.2 with R=15.22 
(Cenko et al. GCN 6306), we calculate the following R-band magnitudes and 
5-sigma upper limits:

t_start (UT)	exp t_tot (s)	Nsum	t_start-t_0 (s)	R Mag
----------------------------------------------------------------
10:01:08.1	10		1	102		R > 17.71
10:01:08.1	50		5	102		R > 18.58
10:02:33.1	20		1	187		R > 18.24
10:02:33.1	100		5	187		R > 19.19
10:04:47.9	60		1	322		R > 18.60
10:07:01.8	60		1	456		R = 18.49 +/- 0.22

Additional observations followed our initial set and analysis are ongoing.