TITLE:   GCN CIRCULAR
NUMBER:  24946
SUBJECT: GRB 190701A: COATLI Optical Observations
DATE:    19/07/01 19:51:59 GMT
FROM:    Rosa Leticia Becerra Godinez at Inst. de Astronoma,UNAM  <rbecerra@astro.unam.mx>

Rosa L. Becerra (UNAM), Alan M. Watson (UNAM),  Nat Butler (ASU),
Diego González (UNAM),Alexander Kutyrev (GSFC), William H. Lee (UNAM),
Margarita Pereyra (UNAM), and Eleonora Troja (GSFC) report:

We observed the field of GRB 190701A (Ukwatta et al., GCN Circ.
24934) 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 2019-07-01 09:47:03 to 10:05:06
(from 25.6 seconds after the alert or 103 seconds to 0.33 hours after
the trigger), obtaining a total of 490 seconds of exposure in the w filter.

Comparing to the USNO and Pan-STARRS1 catalogs, we do not detect any new
sources brighter than w = 20.99 (3-sigma limiting mag) in the XRT error
region
(Osborne et al., GCN Circ. 24940).

Our w magnitudes are calibrated against the Pan-STARRS1 catalog, are on
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
Astronómico Nacional.