[vsnet-grb-info 20708] GRB 180620A: COATLI Detection and Light Curve

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22806
SUBJECT: GRB 180620A: COATLI Detection and Light Curve 
DATE:    18/06/20 15:16:55 GMT
FROM:    Alan M. Watson at Instituto de Astronomia UNAM  <alan at astro.unam.mx>

Alan M. Watson (UNAM), Nat Butler (ASU), Rosa L. Becerra (UNAM), William
H. Lee (UNAM), Carlos Román-Zúñiga (UNAM), Alexander Kutyrev (GSFC), and
Eleonora Troja (GSFC) report:

We observed the field of GRB 180620A (Evans et al., GCN 22798) with the
COATLI 50-cm telescope and interim imager at the Observatorio
Astronómico Nacional on the Sierra de San Pedro Mártir
(http://coatli.astroscu.unam.mx) from 2018-06-20 08:35:37 to 11:17:31
(from 39.2 seconds after the trigger or 21.1 seconds after the alert to
2.7 hours after the trigger), obtaining a total of 6250 seconds of
exposure in the w filter.

We detect the source reported by Butler et al. (GCN Circ. 22799) with

w = 18.00 +/- 0.02

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

Our light curve shows a sharp initial fall from 16.5 mag to 17.3 mag,
followed by a slower rise to 16.7 mag (also seen by Butler et al.),
followed by a monotonic fall to 19.0 mag.

We thank the COATLI technical team (Fernando Ángeles, Oscar Chapa,
Salvador Cuevas, Alejandro Farah, Jorge Fuentes, Rosalía Langarica,
Fernando Quirós, and Carlos Tejada) and the staff of the Observatorio
Astronómico Nacional.