Margarita Pereyra (UNAM), Alan M. Watson (UNAM), Eleonora Troja (GSFC), Nat
Butler (ASU), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Diego
Gonzalez (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier
Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI), Owen
Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jes��s Gonz��lez (UNAM),
Carlos Rom��n-Z����iga (UNAM), Harvey Moseley (GSFC), John Capone (UMD), V.
Zach Golkhou (U. Wash.), and Vicki Toy (UMD) report:
We observed the field of the candidate afterglow of GRB 191001A (trigger
591604915, Fermi GBM Team, GCN Circ. 25893, Pereyra et al. GCN Circ.
25911), centered at 20:20:47.65 +15:05:03.4, 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 2019/10 2.12 to 2019/10 2.17 UTC (20.08 to 21.45 hours
after the Fermi trigger), obtaining a total of 0.34 hours exposure in the g
and r bands, 0.67 hours exposure in the i band and 0.37 hours exposure in
the i, Z, Y, J, and H bands.
At the position of the transient source AT2019rog discovered independently
by ATLAS and DDOTI, in comparison with the USNO-B1, PS1 and 2MASS catalogs,
we obtain the following upper limits (3-sigma):
g > 23.20
r > 23.01
i > 23.26
Z > 21.40
Y > 21.49
J > 21.22
H > 20.92
These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.
The non-detection implies that the source has faded by about 6 magnitudes
in 20 hours. This is consistent with it being the afterglow of GRB 191001A.
We thank the staff of the Observatorio Astron��mico Nacional in San Pedro