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GCN Circular 35078

GRB 231115A : OHP/T120 optical upper limit
2023-11-17T14:17:47Z (6 months ago)
Damien Turpin at CEA-Saclay <>
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D. Turpin (CEA Paris-Saclay), W. Thuillot (Obs. Paris/IMCCE), D. Souami (Obs. Paris/LESIA), C. Adami (LAM), E. Le Floc'h, D. Götz, F. Schüssler (CEA Paris-Saclay), A. de Ugarte Postigo (OCA/CNRS), S. Basa (Pytheas/OHP/LAM), S. D. Vergani (GEPI, Obs. de Paris), report on behalf of a larger collaboration:

We observed the field of GRB 231115A, likely a Giant flare from a magnetar in M82 (Fermi GBM Team, GCN 35035; Mereghetti et al., GCN 35037, Dalessi et al. GCN 35044, Cheung et al. GCN 35045, Xue et al., GCN 35060, Frederiks et al. GCN 35062) using the T120cm telescope at Observatoire de Haute-Provence (France). We began our observations of the M82 field on 2023 15 November 22:57:23.78 (~7.35h after the INTEGRAL trigger time) with a series of R-band (1400s), V-band (600s) and sdss-i (300s) images. The limiting magnitudes of our images are R> 21.1, V>20.9 and i>19.2 but are strongly reduced in the vicinity of M82 due to its bright diffuse background light.

After inspecting our residual images from the subtraction of both the PS1 catalog images and our archival own M82 images, we do not detect any new source inside the INTEGRAL localization. We also  do not detect any credible counterpart at the location of the transient candidate reported by Kumar et al. GCN 35041.

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

We acknowledge the excellent support from Observatoire de Haute-Provence. 

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