TITLE:   GCN CIRCULAR
NUMBER:  30464
SUBJECT: GRB 210715B: DDOTI Upper Limits on the Afterglow
DATE:    21/07/15 19:22:06 GMT
FROM:    Kin O. C. L. Mendoza at Instituto de Astronoma, UNAM  <koclopez@astro.unam.mx>

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

We observed the field of the Fermi - GBM event GRB 210715.39 (Fermi
Collaboration, GCN Circ. 30463) with the DDOTI wide-field imager at the
Observatorio Astronómico Nacional on Sierra San Pedro Martir (
http://ddoti.astroscu.unam.mx) from 2021-07-15 09:34:11 to 11:26:28 UTC
(16.81 to 129.1 minutes after the trigger).


We observed a region of 20.4 degrees in RA by 20.4 degrees in declination,
with a 3 x 2 grid, centered on the Fermi GBM Final Position RA:  292.63,
DEC: +15.12 (J2000 degrees). This region contains 6 instrumental fields or
about 400 square degrees. We obtained 16 minutes of exposure per
instrumental field in the w filter. We obtained AB photometry by
calibration against the APASS catalog.


Comparing to the Pan-STARRS DR1 catalog, we detect no uncatalogued point
sources to a 10-sigma limiting magnitude of w = 19.2 - 19.6

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