[vsnet-grb-info 15014] GRB 140518A: Continued RATIR Optical and NIR Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16308
SUBJECT: GRB 140518A: Continued RATIR Optical and NIR Observations
DATE:    14/05/19 15:01:09 GMT
FROM:    Nat Butler at Az State U  <natbutler at 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
(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 140518A (Melandri, et al., GCN 16298) 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 2014/05 19.24 to 2014/05 19.46 UTC (20.37 to
25.71 hours after the BAT trigger), obtaining a total of 2.47 hours
exposure in the r and i bands and 2.06 hours exposure in the Z an J bands.

For a source at the optical transient position (Zheng et al., GCN 16299),
in comparison with the SDSS DR9 and 2MASS, we obtain the following upper
limits (3-sigma):

  r  > 22.03
  i  > 22.20
  Z  > 21.28
  J  > 21.07

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.  Compared to our observations last
night (Cucchiara, et al., GCN 16302), during which the source faded
approximately as t^(-0.5), the source has now apparently faded more rapidly
as t^(-1) or faster.

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