[vsnet-grb-info 13067] GRB 130418A: Continued RATIR Optical and NIR Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  14404
SUBJECT: GRB 130418A: Continued RATIR Optical and NIR Observations
DATE:    13/04/20 07:11:53 GMT
FROM:    Nat Butler at Az State U  <natbutler at asu.edu>

Subject: Subject: GRB 130418A: Continued RATIR Optical and NIR Observations

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 re-observed the field of GRB 130418A (De Pasquale, et al., GCN 14377)
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 20.14 to 2013/04 20.26 UTC
(32.30 to 35.30 hours after the BAT trigger), obtaining a total of 2.13
hours exposure in the r' and i' bands and 0.89 hours exposure in the Z, Y,
J, and H bands.

Relative to our observations last night (GCN 14388), the GRB afterglow has
faded significantly, by approximately 3 magnitudes in all bands.  In
comparison with SDSS DR8 and 2MASS, we find:

  r'    21.74 +/- 0.12
  i'    21.80 +/- 0.16
  Z     21.52 +/- 0.26
  Y     21.01 +/- 0.21
  J     20.65 +/- 0.17
  H     20.98 +/- 0.35

These magnitudes are in the AB system and not corrected for Galactic
extinction in the direction of the GRB.  Uncertainties are 1-sigma.

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