[vsnet-grb-info 20555] GRB 180418A: RATIR Optical Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22652
SUBJECT: GRB 180418A: RATIR Optical Observations
DATE:    18/04/18 12:45:53 GMT
FROM:    Eleonora Troja at GSFC  <eleonora.troja at nasa.gov>

Eleonora Troja (GSFC), Nat Butler (ASU), Alan M. Watson (UNAM),
Alexander Kutyrev (GSFC), William H. Lee (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), 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 180418A (D'Elia, et al., GCN 22646) 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 2018/04 18.28 to 2018/04 18.43 UTC
(1.8 minutes to 3.64 hours after the BAT trigger), obtaining a total of
2.57 hours exposure in the r and i bands.

At the position of the optical afterglow (Zheng & Filippenko, GCN 22647),
in comparison with the SDSS DR9 catalog, we obtain the following
detection:

   r    = 19.95 +/- 0.01

This magnitude is in the AB system and is not corrected for Galactic
extinction in the direction of the GRB.

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

Further observations are planned.