GCN Circular 18098
Subject
GRB 150728A: Continued RATIR Optical Observations
Date
2015-07-31T17:52:51Z (10 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), 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), Jos� A. de Diego (UNAM), Leonid Georgiev (UNAM),
Jes�s Gonz�lez (UNAM), Carlos Rom�n-Z��iga (UNAM), Neil Gehrels (GSFC),
and Harvey Moseley (GSFC) report:
We observed the field of GRB 150728A (Krimm et al., GCN 18087) 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 2015/07 31.22 to 2015/07 31.46 UTC (64.53 to
70.24 hours after the BAT trigger), obtaining a total of 3.60 hours
exposure in the r, i, and z bands.
For source A of Watson et al. (GCN 18096), we determine:
r 21.26 � 0.04
i 20.90 � 0.04
z 19.43 � 0.13
For source B of Watson et al. (GCN 18096), we determine:
r 20.91 � 0.04
i 20.70 � 0.04
z 20.48 � 0.31
These magnitudes are in comparison with the USNO-B1 and 2MASS catalogs,
are in the AB system, and are not corrected for Galactic extinction in the
direction of the GRB.
Our source A appears to correspond to the source reported by Dichiara et
al. (GCN 18090). If this association is correct, then there is little
evidence for fading between observations at about 1 hour, 16-23 hours, and
65-70 hours. This is in contrast to the suggestion of Mazaeva et al. (GCN
18097), who suggested that source A might indeed be the fading afterglow
on the basis of a 3-sigma non-detection at 30 hours.
Similarly, there is little evidence for fading of source B between 16-23
hours and 65-70 hours.
We thank the staff of the Observatorio Astron�mico Nacional in San Pedro
M�rtir.