[vsnet-grb-info 16481] GRB 150424A: RATIR Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17762
SUBJECT: GRB 150424A: RATIR Observations
DATE:    15/04/25 17:26:07 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 the short-duration GRB 150424A (Beardmore, et al.,
GCN 17743) 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 2015/04 25.14 to 2015/04
25.28 UTC (19.54 to 23.05 hours after the BAT trigger), obtaining a total
of 2.4 hours exposure in the r, i, and z bands.

The optical afterglow (Perley, GCN 17745; Marshall & Beardmore, GCN 17751;
Malesani, et al., GCN 17756; Kann, et al., GCN 17757) is well-detected.  In
comparison with 2MASS and the USNO-B1 catalog, we obtain the following
detections and upper limit (3-sigma):

  r     21.92 +/- 0.11
  i     21.65 +/- 0.09
  z     > 20.17

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.  Compared to the earlier NOT and
GROND observations, the source appears to be continuing its strong fade
(Kann, et al. GCN 17757).

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