TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3414
SUBJECT: GRB 050509b: RAPTOR deep, early limits.
DATE:    05/05/11 22:18:35 GMT
FROM:    Przemyslaw R. Wozniak at LANL  <wozniak@lanl.gov>

P. Wozniak, W.T. Vestrand, J. Wren, S. Evans, and R. White,
on behalf the RAPTOR team at Los Alamos National Laboratory


The RAPTOR-S telescope at Los Alamos National Laboratory responded to
Swift trigger 118749 (Hurkett et al. GCN 3381) and collected a series of
113 unfiltered images starting at 26.57 s and continuing for the first
90 minutes after the trigger. The exposure durations are 10 s for the
first 10 images, 30 s for the next 10 images and 60 s for the remaining
93 images.

Using difference imaging techniques, comparing individual images as well
as stacks of images, we have placed limits on early time variability at
the locations of sources S1-S4 (Cenko et al. GCN 3401) within the XRT
error circle (Rol et al. GCN 3395). We find no evidence for transient
emission at the four candidate locations with the following 5 sigma
limits.

time of mid  limiting  # of    effective  t-t_trig  t-t_trig  UT
exp. (s)     mag (R)   images  duration   start (s) end (s)   start
             (5 sigma)
 
  31.6       18.8       1        10.0       26.6      36.6    04:00:45.8
 193.9       20.0      10       100.0       26.6     220.4    04:00:45.8
 395.3       20.8      10       300.0      234.0     629.3    04:04:13.3
1399.5       21.7      20      1200.0      642.9    2042.4    04:11:02.1
1402.7       21.8      19      1140.0     2052.9    3455.6    04:34:32.1
1399.8       21.6      19      1140.0     3466.0    4865.8    04:58:05.2

The conversion of our unfiltered PSF fluxes to R-band magnitudes was
performed using measurements of 10 nearby comparison stars from the USNO
B1.0 catalog. Sample RAPTOR-S images will be posted at
http://www.raptor.lanl.gov/images/GRB050509/grb050509_raptorS.gif.