TITLE:   GCN CIRCULAR
NUMBER:  14496
SUBJECT: GRB 130427B: RATIR Optical and NIR Observations
DATE:    13/04/29 01:39:53 GMT
FROM:    Nat Butler at Az State U  <natbutler@asu.edu>

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 (UCSC),
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 GRB 130427B (Maselli, et al., GCN 14460) 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 2013/04 28.44 to 2013/04 28.48 UTC (21.26 to
22.19 hours after the BAT trigger), obtaining a total of 0.71 hours
exposure in the r' and i' bands and 0.29 hours exposure in the Z, Y, J, and
H bands.

For a source within the Swift-XRT error circle (Osborne, et al., GCN
14467), in comparison with USNO-B1 and 2MASS, we obtain the following upper
limits (3-sigma):

  r' > 22.08
  i' > 22.06
  Z  > 21.28
  Y  > 20.77
  J  > 20.57
  H  > 19.84

These limits,  in the AB system and not corrected for Galactic extinction
in the direction of the GRB, were derived from PSF-fitting photometry,
because of the presence of a 16.5 magnitude star only 5 arcseconds to the
south of the SWIFT-XRT source position.

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