[vsnet-grb-info 14106] GRB 131030A: RATIR Optical and NIR Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  15420
SUBJECT: GRB 131030A: RATIR Optical and NIR Observations
DATE:    13/10/31 17:08:16 GMT
FROM:    Owen Littlejohns at Az State U  <olittlej at asu.edu>

Owen Littlejohns (ASU), 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), 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 GRB 131030A (Troja, et al., GCN 15402) 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 2013/10 31.08 to 2013/10 31.37 UTC (4.91
to 11.97 hours after the BAT trigger), obtaining a total of 4.26 hours
exposure in the r and i bands and 1.69 hours exposure in the Z,
Y, J, and H bands.

We detect the uncatalogued source reported by UVOT (Troja et al., GCN
Circ. 15414). In comparison with the SDSS DR9 and 2MASS, we obtain the
following detections:

  r     19.14 +/- 0.01
  i     18.92 +/- 0.01
  Z     18.76 +/- 0.02
  Y     18.61 +/- 0.02
  J     18.62 +/- 0.02
  H     18.40 +/- 0.02

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB. We can confirm that this source
fades during our observations with power-law decay indices of approximately
t^-0.9 in the r, i, Z and Y bands and a shallower decay of t^-0.5 and
t^-0.4 in the J and H bands, respectively.

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