GCN Circular 2576

E. Rykoff reports on behalf of the ROTSE collaboration:

The ROTSE-IIIb robotic telescope at McDonald Observatory, Texas, 
responded automatically to INTEGRAL Trigger #1756 (GRB040422) within 8 s 
of the receipt of the first alert, and 22.1 s after the beginning of the 
GRB.  Our response sequence consists of 10 5 s exposures, 10 20 s 
exposures and 200 60 s exposures, all unfiltered.

As the burst was behind the galactic plane, we expect significant 
extinction in our optical passband.  Applying the formula from 
Finkbeiner, Schlegel and Davis (1998), we expect 4.4 magnitudes of 
extinction in the R-band, although they give a caveat that their 
calculations "should not be trusted" at galactic latitudes of |b|<5.

Our first 5-s exposure started at 06:58:27.21 UT.  We visually compared 
our images to the DSS using the revised error circle as reported by 
Mereghetti et. al (GCN 2572
Not found
 
 
).  We find no objects absent from the DSS to 
a limiting magnitude of R ~ 16.5, although field crowding creates 
significant source confusion.  Coadding our first 10 images, with an 
effective exposure time of 110 s, also does not reveal any new objects 
to a limiting magnitude of R ~ 17.5.

Furthermore, no objects in the error box varied significantly over the 
course of our 3.7 hours of observation.