[vsnet-grb-info 28148] GRB 210618A: DDOTI upper limit for the optical afterglow
GCN Circulars
gcncirc at capella2.gsfc.nasa.gov
Fri Jun 18 17:38:26 JST 2021
TITLE: GCN CIRCULAR
NUMBER: 30251
SUBJECT: GRB 210618A: DDOTI upper limit for the optical afterglow
DATE: 21/06/18 08:37:31 GMT
FROM: Kin O. C. L. Mendoza at Instituto de Astronoma, UNAM <koclopez at astro.unam.mx>
Océlotl Lopez (UNAM), Margarita Pereyra (UNAM), Rosa L. Becerra (UNAM),
Nat Butler (ASU), Alan M. Watson (UNAM), Simone Dichiara (GSFC/UMD),
Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Diego Gonzalez (UNAM),
Srihari Ravi (ASU), and Eleonora Troja (GSFC/UMD) report:
We observed the field of the GRB 210618A (Fermi GBM Team, GCN circ. 30248
and Bernardini et al., GCN circ. 30250) with the DDOTI wide-field imager at
the Observatorio Astronómico Nacional on Sierra San Pedro Martir (
http://ddoti.astroscu.unam.mx) from 2021-06-18 03:52:24 UTC to 2021-03-18
06:39:28 UTC (from 2.14 to 4.93 hours after the trigger).
We observed a field of approximately 3.4 degrees in RA and 3.4 degrees in
declination (about 11.55 square degrees), centered on the Swift BAT ground
position of RA 235.74010768 , Dec 46.14225361(J2000), covering the BAT
error region. We obtained 7604.6 seconds of exposure in the w filter. We
calibrated our images against the APASS catalog.
We find no new sources within the BAT error region. To our 10-sigma limit
we obtain an upper limit of w = 20.47 mag for the optical afterglow.
We thank the staff of the Observatorio Astronómico Nacional in San Pedro
Martir.
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