TITLE:   GCN CIRCULAR
NUMBER:  14212
SUBJECT: GRB 130215A: RATIR Optical and NIR Observations
DATE:    13/02/15 10:48:09 GMT
FROM:    Nat Butler at Az State U  <natbutler@asu.edu>

Nat Butler (ASU), Antonino Cucchiara (UCSC), William H. Lee (UNAM),
Alexander Kutyrev (GSFC), Alan M. Watson (UNAM), Michael G. Richer (UNAM),
Chris Klein (UCB), Ori Fox (UCB) J. Xavier Prochaska (UCSC), Josh Bloom
(UCB), 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 130215A (D'Elia et al.; GCN 14204) 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 2013/02 15.13 to 2013/02 15.18 UTC (1.58 to
2.88 hours after the BAT trigger) through intermittent clouds, obtaining a
total of 25 minutes of useful exposure in the r' and i' bands and 19
minutes of useful exposure in the Z and J bands.

We detect the optical counterpart discovered by ROTSE (Zheng et al.; GCN
14205).   In comparison with USNO-B1 and 2MASS, we derive the following
magnitudes in the AB system:

  r' = 17.86 +/- 0.05
  i' = 17.10 +/- 0.04
  Z = 16.86 +/-0.04
  J = 16.67 +/- 0.04

These magnitudes are not corrected for Galactic extinction in the direction
of the GRB.  Compared to the earlier observation at Palomar (Cenko et al;
GCN 14209), our r band magnitude implies a temporal fade by >1 mag on a
timescale of 2 hours, with a corresponding power law fade f ~ t^(-1.5)
between 1 and 3 hours after the GRB.

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