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GCN Circular 32368

GRB 220711B: NOT optical observations
2022-07-11T23:20:15Z (2 years ago)
Daniele B Malesani at Radboud U <>
D. B. Malesani (Radboud Univ. and DAWN/NBI), D. Alexander Kann 
(IAA/CSIC), S. D. Vergani (CNRS - Paris Obs./GEPI), L. Izzo (DARK/NBI), 
O. Durfeldt Pedros (NOT and DTU Space), and T. Pursimo (NOT), report on 
behalf of a larger collaboration:

We observed the field of GRB 220711B (D'Ai et al., GCN 32366) with the 
Nordic Optical Telescope (NOT) equipped with the ALFOSC imager. 
Observations started in twilight in the r band, so that the first images 
are not especially deep. A further set of five 200-s z-band images 
started on 2022 Jul 11.90 UT (3.23 hr after the trigger).

Close to the currently available XRT position, we see three sources in 
the stack of the z-band images (astrometry and photometry are calibrated 
against the Gaia and Pan-STARRS catalogs, respectively):

RA = 17:28:04.49
Dec = +24:40:50.8
z = 21.78 +- 0.13 AB

RA = 17:28:04.44
Dec = +24:40:46.7
z = 22.09 +- 0.15 AB

RA = 17:28:04.97
Dec = +24:40:44.7
z = 22.60 +- 0.19 AB

Sources 2) and 3) are visible in archival images from the Pan-STARRS 
survey, while source 1) is not, which makes it a viable afterglow 
candidate. However, sources 1), and 2) are slightly outside (5.6" and 
5.7" away) the currently available (unenhanced) XRT position (which has 
a 3.6" 90% error radius).

Sources 2) and 3) are also detected in our NOT r-band images, while 
source 1) is not.

The relation of these sources to GRB 220711B is still under 
investigation. Further NOT observations are planned.
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