TITLE: GCN CIRCULAR NUMBER: 26792 SUBJECT: GRB 200115A: DDOTI/OAN optical observations report DATE: 20/01/16 20:59:20 GMT FROM: Emma Margarita Pereyra Talamantes at IA-UNAM Ensenada Rosa L. Becerra (UNAM), Margarita Pereyra (UNAM), Nat Butler (ASU), Alan M. Watson (UNAM), Eleonora Troja (GSFC/UMD), Diego Gonzalez (UNAM), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), and Tanner Wolfram (ASU), Simone Dichiara (GSFC/UMD) report: We observed the field of GRB 200115A detected by BAT/Swift (Cenko, GCN Circ. 26771), with the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir ( http://ddoti.astroscu.unam.mx) from 2020-01-16 02:01 to 2020-01-16 02:19 UTC (14.2 to 14.48 hours after the event). We observed a region of 6.8 degrees in RA by 10.2 degrees in declination centered on the peak of the Swift-BAT on-board calculated location 03:45:48.7 +05:36:26.0 J2000. This region contains about 70 square degrees. We obtained about 16 minutes total exposure across the region. We calibrated our images against the APASS catalog. Our 3-sigma limiting magnitude is w = 19.80 for the enhanced Swift-BAT error region (Laha et al., GCN Circ. 26780). Comparing to the USNO-B1 and SDSS DR9 catalogs we do not detect any uncataloged source to our 3-sigma limit. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir. -- *Dr. Margarita Pereyra * *FFTF, Schlumberger Foundation Alumnae* ---------------------------------------------------------------------------------------------------------------- *Catedrático Conacyt* *Instituto de Astronomía de la UNAM,* *Km. 107 Carretera Tijua**na-Ensenada, * *Ensenada Baja California, México. C.P. 22860* Oficina: 405 Skype: margarita-pereyra