[vsnet-grb-info 16033] GRB 140120B: P60 optical afterglow

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17315
SUBJECT: GRB 140120B: P60 optical afterglow
DATE:    15/01/20 08:11:39 GMT
FROM:    Daniel Perley at Caltech  <dperley at astro.caltech.edu>

D. A. Perley (Caltech) reports on behalf of a larger collaboration:

The Palomar 60-inch robotic telescope began automatic follow-up of the
location of GRB 150120B (D'Elia et al., GCN 17314) starting at 07:26:07 
UT on 2015-01-20.

In the first three 60-second frames (r, i, and z-bands) we detect a 
bright (r~18.7 mag), new source at the following location (J2000):

RA  =  02:37:09.770
dec = +08:04:40.37

After these three frames, the telescope received the initial XRT 
position notice and it executed a large slew to a new position, and this 
optical source was no longer in the field of view.  It returned to the 
field with the updated XRT position notice in an image starting at 
07:47:47; the GRB afterglow shows significant fading (to r~19.7 mag) in 
this observation since the first epoch, confirming it as the optical 
afterglow.

We also note that the optical position above is near, but significantly 
outside (7 arcsec west) of, the updated XRT position given in GCN 17314.