[vsnet-grb-info 16791] GRB 150724B: RATIR Optical Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  18072
SUBJECT: GRB 150724B: RATIR Optical Observations
DATE:    15/07/27 03:33:50 GMT
FROM:    Alan M. Watson at Instituto de Astronomia UNAM  <alan at astro.unam.mx>

Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William 
H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UCB), 
J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara 
(ORAU/GSFC), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico 
Ramirez-Ruiz (UCSC), José A. de Diego (UNAM), Leonid Georgiev (UNAM), 
Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Neil Gehrels (GSFC), 
and Harvey Moseley (GSFC) report:

We observed the field of the LAT GRB 150724B (Bissaldi et al., GCN 18065) 
with the Reionization and Transients Infrared Camera (RATIR; 
www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio 
Astronómico Nacional on Sierra San Pedro Mártir from 2015/07 26.28 to 
2015/07 26.48 UTC (36.02 to 40.86 hours after the BAT trigger), obtaining 
a total of 2.39 hours exposure in the r and i bands.

For a source within the Swift XRT error circle (Osborne et al., GCN 
18069), in comparison with the SDSS DR9 catalog, we obtain the following 
detections:

   r	23.24 +/- 0.34
   i	22.39 +/- 0.15

These magnitudes are in the AB system and are not corrected for Galactic 
extinction in the direction of the GRB.

At this moment we have no information on fading. Further observations are 
planned.

We thank the staff of the Observatorio Astronómico Nacional in San Pedro 
Mártir.