TITLE:   GCN CIRCULAR
NUMBER:  24644
SUBJECT: LIGO/Virgo S190521g: No Counterparts in DDOTI/OAN Optical Observations
DATE:    19/05/21 20:06:24 GMT
FROM:    Alan M Watson at UNAM  <alan@astro.unam.mx>

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

We observed LIGO/Virgo S190519g (Mo et al, GCN Circ. 24621) with the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir (http://ddoti.astroscu.unam.mx) on the night of 2019-04-21 UTC. 

We observed four fields covering a region of approximately 14 degrees in RA and 21 degrees in declination (280 square degrees) centered on 12:36:00 +28:20:00. This region includes about 20% of the probability in the initial localization map. We observed from 2019-05-21 04:27 UTC to 09:33 UTC (1.5 to 6.6 hours after the event). We obtained about 36 minutes total exposure on each field in the w filter.

We calibrate our images against the APASS catalog. Our 10-sigma limiting magnitude are typically w = 18.7 AB.

Comparing our 10-sigma detections against the USNO-B1 catalog, we detect no uncataloged sources with significant fading.

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