GCN Circular 18156
Subject
GRB 150817A: Continued RATIR Optical Observations - Afterglow Confirmation
Date
2015-08-18T16:29:47Z (9 years ago)
From
Alan M. Watson at Instituto de Astronomia UNAM <alan@astro.unam.mx>
Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William
H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (UCB), J. Xavier
Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (ORAU/GSFC),
Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC),
Jos� A. de Diego (UNAM), Leonid Georgiev (UNAM), Jes�s Gonz�lez (UNAM),
Carlos Rom�n-Z��iga (UNAM), Neil Gehrels (GSFC), Harvey Moseley (GSFC),
John Capone (UMD), V. Zach Golkhou (ASU), and Vicki Toy (UMD) report:
We observed the field of GRB 150817A (D'Elia, et al., GCN 18143) with the
Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the
1.5m Harold Johnson Telescope at the Observatorio Astron�mico Nacional on
Sierra San Pedro M�rtir from 2015/08 18.16 to 2015/08 18.27 UTC (25.78 to
28.42 hours after the BAT trigger), obtaining a total of 1.77 hours
exposure in the r, i, and z bands.
The first source reported by Butler et al. (GCN 18144) has not faded since
our first epoch of observations.
The second source, reported by Butler et al. (GCN 18145), has continued to
fade and is now only marginally detected. In comparison with the USNO-B1
and 2MASS catalogs, we obtain the following marginal detections and upper
limit (3-sigma):
r = 23.8 � 0.4
i = 23.8 � 0.3
z > 20.2
These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.
We note that the second source is consistent with the enhanced Swift-XRT
error circle (Osborne et al. GCN 18146). This coincidence and the clear
fading suggest that it is the afterglow of the GRB.
We thank the staff of the Observatorio Astron�mico Nacional in San Pedro
M�rtir.