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GCN Circular 32753

GRB 221009A: OHP optical observations
2022-10-14T12:40:52Z (2 years ago)
Benjamin Schneider at CEA <>
B. Schneider (CEA Paris-Saclay), C. Adami (LAM), E. Le Floc'h, 
D. Turpin, D. G��tz (CEA Paris-Saclay) S. D. Vergani, A. Saccardi 
(GEPI, Observatoire de Paris), S. Basa, A. Le Van Suu (LAM) report 
on behalf of a larger collaboration:

We observed the field of GRB 221009A (Dichiara et al., GCN 32632; 
Veres et al., GCN 32636) using the T120cm telescope at Observatoire 
de Haute-Provence (France). Four exposures were obtained in the 
r band (2x300s + 2x600s), three exposures in the i band (3x600s) 
and the z band (1x300s + 2x900s) from 2022 12 Oct 19:11:05 UT to 
2022 12 Oct 20:41:23 UT (mid time ~78h after trigger). In the 
combined frame, we clearly detect the source in the three filters 
and obtain the following magnitudes:

r = 20.23 �� 0.09 mag (AB)
i = 18.91 �� 0.11 mag (AB)
z = 18.35 �� 0.13 mag (AB)

The photometric calibration was performed using nearby stars from 
the PanSTARRS catalog and magnitudes are not corrected for Galactic 

These values are consistent with observations obtained at a similar 
time by Bikmaev et al. (GCN 32743).

Further observations using the MISTRAL instrument mounted on the 
T193-OHP are planned for the coming nights.

We acknowledge the excellent support from Observatoire de Haute Provence, 
in particular Fran��ois Huppert and J��rome Schmitt.
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