[vsnet-grb-info 21297] GRB 181030A: RATIR Optical and NIR Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23396
SUBJECT: GRB 181030A: RATIR Optical and NIR Observations 
DATE:    18/10/30 15:56:06 GMT
FROM:    Alan M. Watson at Instituto de Astronomia 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 181030A (Sonbas et al., GCN Circ. 23389)
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 2018/10 30.41 to
2018/10 30.53 UTC (8.40 to 11.29 hours after the BAT trigger), obtaining
a total of 0.82 hours exposure in the r and i bands and 0.39 hours
exposure in the Z, Y, J, and H bands.

For a source within the XRT error circle, in comparison with the SDSS
DR9 and 2MASS catalogs, we obtain the following upper limits (3-sigma):

  r	> 22.25
  i	> 22.11
  Z	> 21.07
  Y	> 20.80
  J	> 20.31
  H	> 19.61

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

The afterglow has clearly faded since the early observations of Sonbas
et al. (GCN Circ. 23389), Moskvitin & Spiridonova (GCN Circ. 23390), and
Lipunov et al. (GCN Circ. 23392).

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