TITLE:   GCN CIRCULAR
NUMBER:  27061
SUBJECT: LIGO/Virgo S200213t: No Counterparts in DDOTI/OAN Optical Observations 
DATE:    20/02/13 23:46:25 GMT
FROM:    Alan M Watson at UNAM  <alan@astro.unam.mx>

Alan M. Watson (UNAM), Nat Butler (ASU), Margarita Pereyra (UNAM),
William H. Lee (UNAM), Simone Dichiara (GSFC/UMD), Alexander Kutyrev
(GSFC/UMD), Margarita Pereyra (UNAM), Rosa L. Becerra (UNAM), Diego
Gonzalez (UNAM), Eleonora Troja (GSFC/UMD), and Tanner Wolfram (ASU)
report:

We observed LIGO/Virgo S200213t (Singer et al, GCN Circ. 27042) with the
DDOTI/OAN wide-field imager at the Observatorio Astronomico Nacional on
Sierra San Pedro Martir (http://ddoti.astroscu.unam.mx) on the night of
2020-02-13 UTC.

We tiled the LVC localization with three pointings centered on
00:50:27.6 +49:57:20, 01:09:34.1 +55:40:56, and 01:46:40.1 +57:01:56
(J2000). The combined field covers about 200 square degrees and includes
about 50% of the probability in the current BAYESTAR map.

We observed from 2020-02-13 04:55 UTC to 2020-02-13 07:05 UTC (from 0.75
to 2.92 hours after the event) obtaining exposures of 24 to 44 minutes
across the field in the w filter. We calibrate our images against the
APASS catalog. Our 10-sigma limiting magnitude are between w = 18.7 and
w = 19.2.

Comparing our observations to the USNO-B1 and PanSTARRS PS1 DR2
catalogs, with the exception of Comet C/2017 T2, we detect no
uncatalogued sources within the observed field to our 10-sigma limit.

We thank the staff of the Observatorio Astronomico Nacional in San Pedro
Martir.