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GCN Circular 33607

GRB 230409B: OHP/T193 optical upper limit
2023-04-12T13:30:17Z (a year ago)
Benjamin Schneider at MIT <>
C. Adami (LAM), B. Schneider (MIT), S. Basa (LAM), 
E. Le Floc'h, D. Turpin, D. G��tz (CEA Paris-Saclay), 
S. D. Vergani (GEPI, Obs. de Paris), report on behalf 
of a larger collaboration:

We observed the field of GRB 230409B (Beardmore et al., GCN 33592) 
using the T193cm telescope at Observatoire de Haute-Provence (France) 
equipped with the MISTRAL spectro-imager. Four exposures were obtained 
in the i-band (2x300s + 2x600s) from 2023 10 April 03:03:03 UT to 
2023 10 April 03:44:17 UT (mid time ~22.3h after trigger). In the combined 
frame, we do not detect any source at the position reported by Evans et al., 
GCN 33594 and Kuin et al., GCN 33595 down to the following 3-sigma limit:

i > 20.6 mag (AB)

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

We acknowledge the excellent support from Observatoire de Haute-Provence, 
in particular Jean-Pierre Troncin.
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