[vsnet-grb-info 28490] GRB 210802A: DDOTI Upper Limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30593
SUBJECT: GRB 210802A: DDOTI Upper Limits 
DATE:    21/08/04 00:14:44 GMT
FROM:    Alan M Watson at UNAM  <alan at astro.unam.mx>

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

We observed the field of the Fermi GBM/LAT event GRB 210802A (Longo et al., GCN
Circ., 30589; Roberts et al., GCN Circ., 30590) with the DDOTI wide-field imager
at the Observatorio Astronómico Nacional on Sierra San Pedro Martir (
http://ddoti.astroscu.unam.mx) from 2021-08-03 03:35 to 07:37 UTC (7.45 to 11.48
hours after the trigger).

We observed a region of about 14 degrees in RA by 10 degrees in declination,
with a 1 x 2 grid of pointings centered on the Fermi GBM Final Position
15:19:40.80 +30:18:00.0 (J2000) and including the entire LAT uncertainty region
(Longo et al., GCN Circ., 30589). We obtained about 105 minutes exposure on the
LAT uncertainty region. We obtained AB photometry by calibration against the
APASS catalog.

Comparing to the Pan-STARRS DR1 catalog, we detect no uncatalogued point sources
in the LAT uncertainty region to a 10-sigma limiting magnitude of w = 21.0.

At the position of the candidate X-ray afterglow (Sbarufatti et al., GCN Circ.,
30591), we detect no point source to a 5-sigma limiting magnitude of w = 21.8.

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