GCN Circular 23861
Subject
GRB 190204A: COATLI Optical Detection of the Fading Afterglow
Date
2019-02-04T12:54:35Z (5 years ago)
From
Alan M. Watson at Instituto de Astronomia UNAM <alan@astro.unam.mx>
Alan M. Watson (UNAM), Nat Butler (ASU), Rosa L. Becerra (UNAM), Diego
Gonz��lez (UNAM), William H. Lee (UNAM), Margarita Pereyra (UNAM), Carlos
Rom��n-Z����iga (UNAM), Alexander Kutyrev (GSFC), and Eleonora Troja (GSFC)
report:
We observed the field of GRB 190204A (Lien et al., GCN Circ. 23852) with
the COATLI 50-cm telescope and interim imager at the Observatorio
Astron��mico Nacional on the Sierra de San Pedro M��rtir
(http://coatli.astroscu.unam.mx) from 2019-02-04 05:46:35 to 2019-02-04
05:57:30 (from 34 to 689 seconds after the trigger), obtaining a total
of 345 seconds of exposure in the w filter.
At the position of the UVOT afterglow candidate (Lien et al., GCN Circ.
23852), we detect a source that fades from w = 13.5 to w = 17.5 over the
course of our observations. A power-law fit suggest a temporal index of
-1.44 +/- 0.03.
Our w magnitudes are calibrated against the USNO-B1 catalog (adjusted to
an approximate AB system) and are not corrected for Galactic extinction
in the direction of the GRB.
We thank the COATLI technical team and the staff of the Observatorio
Astron��mico Nacional.