TITLE: GCN CIRCULAR NUMBER: 25416 SUBJECT: LIGO/Virgo S190814bv: RATIR Optical observations of DECam transients DATE: 19/08/20 21:20:46 GMT FROM: Simone Dichiara at UMCP/NASA/GSFC Simone Dichiara (GSFC/UMD), Eleonora Troja (GSFC/UMD), Alan M. Watson (UNAM), Nat Butler (ASU), Rosa L. Becerra (UNAM), Diego Gonzalez (UNAM), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Margarita Pereyra (UNAM), Gabriele Minervini (INAF-IAPS) and Tanner Wolfram (ASU) report: We observed the field of the optical transients detected with DECam (Goldstein et al., GCN Circ. 25393; Herner et al. 25373) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astronomico Nacional on Sierra San Pedro Martir from 2019/08 20.30 to 2019/08 20.50 UTC, obtaining a total of about 10 minutes exposure on each field in the r band. We detect the following candidates with magnitudes: NAME START TIME EXP(sec) r_MAG ERR DG19sbzkc 07:16:14 1280 20.87 0.21 DG19gcwjc 08:18:23 1280 19.53 0.06 (a) desgw-190814e 08:57:59 1200 18.14 0.03 (a) desgw-190814c 09:28:55 1120 20.13 0.08 DG19rzhoc 10:03:38 1280 19.11 0.04 (a) DG19kpykc 10:35:55 1200 18.28 0.03 (a) DG19hqhjc 11:17:00 1280 20.79 0.12 (a) the object is in the central part of the galaxy Photometric measurements are contaminated by host galaxy light. We also observed at the position of DG19wlpmc and DG19rtekc, but we do not detect any object down to a magnitude of ~22 and ~21, respectively. These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the source. We thank the staff of the Observatorio Astronomico Nacional in San Pedro Martir.