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GCN Circular 30135

Fermi GRB 210606A: DDOTI Upper Limits on the Afterglow
2021-06-06T19:29:35Z (3 years ago)
Emma Margarita Pereyra Talamantes at IA-UNAM Ensenada <>
Margarita Pereyra (UNAM), Alan M. Watson (UNAM), Nat Butler (ASU), Camila
Angulo,  Simone Dichiara (GSFC/UMD), Rosa L. Becerra (UNAM), William H. Lee
(UNAM), Oc��lotl L��pez,  Eleonora Troja (GSFC/UMD), Diego Gonzalez (UNAM),
Alexander Kutyrev (GSFC/UMD), and Srihari Ravi (ASU), report:

We observed the field of the likely Long Fermi GRB 210606A  (trigger
644644567, GCN #30131, Fermi GBM Team) with the DDOTI/OAN wide-field imager
at the Observatorio Astron��mico Nacional on Sierra San Pedro M��rtir ( on 2021/06/06 from 04:12:31.000 to
06:46:24.000 UTC (0.27 to 2.83 hours after the event).

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: 177.630000,
DEC: -0.470000 (J2000 degrees). This region contains 6 instrumental fields
or about 400 square degrees. We obtained 1075 to 1200 seconds of exposure
per instrumental field in the w filter. We obtained AB photometry by
calibration against the APASS catalog.

We detect no likely candidates for the afterglow to our 10-sigma upper
limits of w = 19.64 to 19.93 (inter-quartile).

We thank the staff of the Observatorio Astron��mico Nacional in San Pedro
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