TITLE:   GCN CIRCULAR
NUMBER:  15928
SUBJECT: GRB 140304A: RATIR g-band Dropout
DATE:    14/03/05 04:59:08 GMT
FROM:    Nat Butler at UC berkeley  <natxbutler@gmail.com>

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), 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 140304A (Evans, et al., GCN 15915) 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 2014/03 5.12 to 2014/03 5.16 UTC (13.50 to
14.40 hours after the BAT trigger), obtaining a total of 0.26 hours
exposure in the g and r bands, 0.53 hours exposure in the i band, and 0.30
hours exposure in the Z, Y, J, and H bands.

For a source within the Swift-XRT error circle (Evans, et al., GCN 15925),
in comparison with the SDSS DR9 and 2MASS, we obtain the following
detections and 3-sigma upper limit:

  g     > 23.07
  r     21.78 +/- 0.13
  i     20.66 +/- 0.06
  Z    19.45 +/- 0.05
  Y    19.19 +/- 0.06
  J     19.11 +/- 0.07
  H     18.71 +/- 0.08

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

Using the procedure outlined in Littlejohns et al. 2013 (arXiv:1312.3967),
we derive a photometric redshift z_phot = 5.45 (-0.2,+0.1; 90% confidence).
 This photometric redshift is consistent with the one reported by de
Ugarte-Postigo et al. (GCN 15921) and the spectroscopic redshift
determinations by Jeong et al. (GCN 15922) and de Ugarte-Postigo et al.
(GCN 15924).

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