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GCN Circular 36101

GRB 240414A : OHP/T193 second epoch of optical follow-up and afterglow detection
2024-04-14T21:59:49Z (a month ago)
Damien Turpin at CEA-Saclay <>
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D. Turpin (CEA Paris-Saclay), B. Schneider (MIT), C. Adami, Ny Avo Rakotondrainibe, Olivier Ilbert, S. Basa (LAM/Pytheas/AMU), A. de Ugarte Postigo (OCA/LAM), E. Le Floc'h (CEA Paris-Saclay), S. D. Vergani (GEPI, Obs. de Paris), report on behalf of a larger collaboration:

We performed a second epoch of observation of the GRB 240414A afterglow candidate (Caputo et al., GCN 36083, Schneider et al. GCN 36084, Dutton et al. GCN 36097) using the T193cm telescope at Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. After stacking 8 r-band images (total exp = 4080sec), we clearly detect the optical afterglow with the following preliminary magnitude:
T-T0 (in days, midtime) | mag | filter
0.7397 | 21.84 ± 0.16 mag (AB) | r'

We also report the g-band magnitude of the afterglow for the previous night (2x120s):
T-T0 (in days, midtime) | mag | filter
0.0645 | 18.39 ± 0.03 mag (AB) | g'
Based on our two epochs in r-band, we obtain a temporal slope alpha ~ -1.1 which is roughly consistent with the one of Dutton et al. GCN 36097.

We acknowledge the excellent support from Observatoire de Haute-Provence and in particular Jean-Pierre Troncin for the MISTRAL observations.
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