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GCN Circular 40944

Subject
GRB 250704A: REM retraction of optical afterglow detection and updated limit
Event
GRB 250704A
Date
2025-07-04T10:52:18Z (2 days ago)
From
Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it>
Via
Web form
R. Brivio, M. Ferro (INAF-OAB), A. Rossi (INAF-OAS), P. D'Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team:

Further analysis of the optical data obtained with REM (Brivio et al. GCN Circ. 40938) reveals that the source identified as the optical afterglow of GRB 250704A (Cao et al., GCN Circ. 40934) is spurious, likely resulting from a cosmic ray. From further analysis of the field, we obtain a 3sigma upper limit of:
r > 18.1 (AB; calibrated against the Pan-STARRS catalogue),
at a mid-time of 1.7 hr after the trigger.

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