TITLE: GCN CIRCULAR NUMBER: 27402 SUBJECT: LIGO/Virgo S200316bj: No Counterparts in DDOTI/OAN Optical Observations DATE: 20/03/17 20:43:18 GMT FROM: Emma Margarita Pereyra Talamantes at IA-UNAM Ensenada Margarita Pereyra (UNAM), Alan M. Watson (UNAM), Nat Butler (ASU), Simone Dichiara (GSFC/UMD), Eleonora Troja (GSFC/UMD), William H. Lee (UNAM), Alexander Kutyrev (GSFC/UMD), Rosa L. Becerra (UNAM), Diego Gonzalez (UNAM), and Tanner Wolfram (ASU) report: We observed LIGO/Virgo S200316bj (LIGO/Virgo Collaboration, GCN Circ. 27388) with the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on Sierra San Pedro Martir (http://ddoti.astroscu.unam.mx) on the night of 2020-03-17 UTC. We tiled the LVC localization with two pointings centered on 05:39:01.45 +47:47:45.23 and 05:50:02.85 +46:24:27.21 (J2000). The combined field covers about 81 square degrees and includes about 30% of the probability in the current BAYESTAR map. We observed from 2020-03-17 02:44 UTC to 2020-03-17 04:27 UTC (from 4.78 to 6.5 hours after the event) obtaining exposures of 28 to 45 minutes across the field in the w filter, with 10-sigma limiting magnitudes of w = 18.2 to w = 18.8. We calibrate our images against the APASS catalog. Comparing our observations to the USNO-B1 and PanSTARRS PS1 DR2 catalogs we detect no uncatalogued sources within the observed field to our 10-sigma limit. However, we do detect the previously-cataloged transient source AT 2019dgf at w = 16.8. We thank the staff of the Observatorio Astronomico Nacional in San Pedro Martir. -- *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