[vsnet-grb-info 20998] GRB 180806A/180806.98: RATIR Optical Observations of MASTER OT J004613.05+242014.1

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23096
SUBJECT: GRB 180806A/180806.98: RATIR Optical Observations of MASTER OT J004613.05+242014.1 
DATE:    18/08/07 17:52:13 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 the Fermi GRB 180806A/180806.98 (Malacaria et
al., GCN Circ. 23095) 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
2018/08 7.47 to 2018/08 7.51 UTC (12.69 to 13.71 hours after the GBM
trigger), obtaining a total of 0.71 hours exposure in the r and i bands.

We detect a source at the coordinates of the MASTER OT reported by
Lipunov et al. (GCN Circ. 23091). In comparison with the SDSS catalog,
we obtain the following magnitudes:

r = 20.21 +/- 0.02 
i = 19.92 +/- 0.01

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

These magnitudes are similar to the w magnitude reported by Butler et
al. (GCN Circ. 23094) and further confirm the fading compared to the
earlier MASTER magnitude reported by Watson et al. (GCN Circ. 23092).

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