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GCN Circular 22799

GRB 180620A: RATIR Optical Afterglow Detection
2018-06-20T09:16:28Z (6 years ago)
Nat Butler at Az State U <>
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), Eleonora Troja (GSFC), 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 GRB 180620A (Evans, et al., GCN 22798) with the
Reionization and Transients Infrared Camera (RATIR; on the
1.5m Harold Johnson Telescope at the Observatorio Astron��mico Nacional on
Sierra San Pedro M��rtir from 2018/06 20.36 to 2018/06 20.38 UTC (0.03
to 0.47 hours after the BAT trigger), obtaining a total of 0.36 hours
exposure in the r and i bands.

For a source within the Swift-XRT error circle, in comparison with the
USNO-B1 and 2MASS catalogs, we
obtain the following detections:

  r	= 18.01 +/- 0.01
  i	= 17.71 +/- 0.01

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.  We observe the rise and
initial decline of the afterglow.

We thank the staff of the Observatorio Astron��mico Nacional in San Pedro
M��rtir.  Further observations are planned.
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