[vsnet-grb-info 13878] GRB 130907A: RATIR Optical and NIR Afterglow Confirmation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  15192
SUBJECT: GRB 130907A: RATIR Optical and NIR Afterglow Confirmation
DATE:    13/09/08 05:11:53 GMT
FROM:    Alan M. Watson at Instituto de Astronomia UNAM  <alan at astro.unam.mx>

William H. Lee (UNAM), Nat Butler (ASU), Alan M. Watson (UNAM),
Alexander Kutyrev (GSFC), 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 130907A (Page et al., GCN 15183) 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 2013/09 8.14 to 2013/09 8.15 UTC (5.57
to 6.03 hours after the BAT trigger), obtaining a total of 0.36 hours
exposure in the r and i bands and 0.15 hours exposure in the Z,
Y, J, and H bands.

We detect a source at 14:23:34.01 +45:36:27.0 J2000 (+/- 0.5") with

  r = 20.01 +/- 0.03
  i = 19.30 +/- 0.02
  Z = 18.78 +/- 0.05
  Y = 18.48 +/- 0.06
  J = 18.13 +/- 0.06
  H = 17.63 +/- 0.05

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

This source is outside the Swift-XRT error circle, but is only 0.8
arcsec from the transient source reported by de Ugarte Postigo et al.
(GCN 15187) and 0.2 arcsec from the transient source reported by Trotter
et al. (GCN 15191). From the close positional coincidence and fading
magnitudes (r of 16.7, 19.6, and 20.0), we conclude all three
observations are of the optical transient.

The transient source is 0.5 arcsec from the faint galaxy SDSS
J142333.95+453626.2, but is 1-2 magnitudes brighter in riZ.

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