[vsnet-grb-info 21557] GRB 190109B: COATLI Optical Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23656
SUBJECT: GRB 190109B: COATLI Optical Observations
DATE:    19/01/09 16:11:22 GMT
FROM:    Alan M. Watson at Instituto de Astronomia UNAM  <alan at astro.unam.mx>

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

We observed the field of GRB 190109B (Sbarufatti et al., GCN Circ.
23642) 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 2019-01-09 11:57:47.6 to
13:27:45.2 (from 98.5 seconds to 1.53 hours after the trigger) at air
masses above 3, obtaining a total of 59.1 minutes of exposure in the w
filter.

We do not detect an optical source within the enhanced XRT position
region (Beardmore et al., GCN Circ. 23652) to a 5-sigma limiting
magnitude of w = 20.3.

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
Astronómico Nacional.