TITLE:   GCN CIRCULAR
NUMBER:  28957
SUBJECT: Fermi trigger No 628140709: DDOTI/OAN optical observations report
DATE:    20/11/27 23:56:46 GMT
FROM:    Emma Margarita Pereyra Talamantes at IA-UNAM Ensenada  <mpereyra@astro.unam.mx>

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

We observed the field of Fermi trigger 628140709 with the DDOTI/OAN
wide-field imager at the Observatorio Astronómico Nacional on Sierra San
Pedro Mártir (http://ddoti.astroscu.unam.mx) on 2020-11-27 from 06:49 to
13:04 UTC (3.3 to 9.5 hours after the event).

We observed a region of 20.4 degrees in RA by 20.4 degrees in declination,
with a 3 x 2 grid, centered on the Fermi GBM Final Position 143.68d +
42.730d (J2000). This region contains about 416.2 square degrees. We
obtained 2400 to 2760 seconds exposure, 4.32hrs on average, across the
region. We calibrated our images against the APASS catalog. Our 10-sigma
limiting magnitude is around w = 19.92.

Compared to the USNO-B1, DSS DR2 and Pan-STARRS DR1 catalogs, we do not
detect any uncataloged source with significant fading within the 90%
probability radius of 6.58 degrees.

We thank the staff of the Observatorio Astronómico Nacional in San Pedro
Mártir.