[vsnet-grb-info 23916] GRB 191016A: RATIR Optical and NIR Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  26015
SUBJECT: GRB 191016A: RATIR Optical and NIR Observations 
DATE:    19/10/17 01:31:15 GMT
FROM:    Alan M Watson at UNAM  <alan at astro.unam.mx>

Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William H.
Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska
(UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI), Eleonora Troja (GSFC), Owen
Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jesús González (UNAM), Carlos
Román-Zúñiga (UNAM), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou
(U. Wash.), and Vicki Toy (UMD) report:

We observed the field of GRB 191016A (Gropp et al., GCN Circ. 26008) 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 2019/10 16.18 to 2019/10 16.26 UTC (0.12 to 2.13 hours after
the BAT trigger), obtaining a total of 0.99 hours exposure in the r and i bands
and 0.54 hours exposure in the Z, Y, J, and H bands.

We detect a source coincident with the COATLI afterglow candidate (Watson et
al., GCN Circ. 26010). In comparison with the SDSS DR9 and 2MASS catalogs, we
obtain the following detections:

  r	= 16.42 +/- 0.00
  i	= 16.16 +/- 0.00
  Z	= 15.91 +/- 0.01
  Y	= 15.78 +/- 0.01
  J	= 15.42 +/- 0.01
  H	= 15.10 +/- 0.01

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.

The light curve shows similar behaviour to that reported by Watson et al. We see
the source rise from r = 16.8 to r = 15.3 before falling to r = 17 at the end of
these observations.

In subsequent observations we added images in the g filter and determined that
the g - r color is 0.44 +/- 0.01. This strongly suggests that the GRB is at z <
4 (Littlejohns et al. 2014).

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