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GCN Circular 36655

Subject
GRB 240529A: LBT optical detection and late temporal decay
Date
2024-06-10T13:22:57Z (3 days ago)
From
Andrea Rossi at INAF <andrea.rossi@inaf.it>
Via
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A. Rossi, E. Maiorano (INAF-OAS), A. Melandri (INAF-OAR), D. B. Malesani (DAWN/NBI and Radboud), L. Izzo (INAF-OACn & DARK/NBI) and M . De Pasquale (Univ. of Messina) report on behalf of the CIBO collaboration:

We observed the field of GRB 240529A  (Eyles-Ferris et al., GCN 36556; Joshi et al., GCN 36560; Tan et al., GCN 36578; Kozyrev et al., GCN 36583  et al. GCN 36583;  Svinkin et al., GCN 36584) with the LBC camera mounted on LBT (Mt Graham, AZ, USA) in u'g'r'i'z' bands approximately at midtime 9:55 UT on 2024-06-05 and 7.3 days after the burst trigger.

The optical transient (Kumar et al. GCN 36559; Fu et al. GCN 36561; Shilling et al. GCN 36562; Perez-Garcia et al. GCN 36563; Dutton et al. GCN 36568; Mo et al. GCN 36569; Odeh et al. GCNs 36573, 36592; de Ugarte Postigo et al. GCN 36574; Adami et al. GCN 36575; Mohan et al. GCN 36576; Vinko et al. GCN 36577;  Lim et al. GCN 36579; Moskvitin et al. GCNs 36582, 36597, 36601 ; Pankov et al. GCN 36585; Ror et al., 36589; Hu et al. GCN 36599; Lipunov et al. GCN 36603) is well detected in r’i’z’  bands. The good seeing (0.8") allows us to detect the afterglow and separate it from a brighter star which is only 1 arcsec away and visible also in PanSTARRS archival images. Using PSF photometry, we measure a preliminary AB magnitude of r'=23.9+-0.1, calibrated against PanSTARRS field stars, and not corrected for the foreground Galactic extinction.

This detection together with the early photometry reported in the GCNs (selected between 5 and 30 hours after the trigger to be less contaminated by the near-by bright-star) are well fitted by a power-law decay with index -1.9, in agreement with the Swift/XRT late-time decay behavior.

We acknowledge the excellent support from the LBTO and LBT-INAF staff, particularly J. Rupert, S. Allanson, F. Cusano, E. Marini, D. Paris, and E. O. Kishka in obtaining these observations.

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