GCN Circular 40929
Subject
GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
Event
Date
2025-07-04T02:24:14Z (a year ago)
From
I. Perez-Garcia at Institute of Astrophysics of Andalusia <ipg@iaa.es>
Via
Web form
I. Pérez-García, A. J. Castro-Tirado, M. D. Caballero-García, S. Guziy, R. Sánchez-Ramírez, S.-Y. Wu (IAA-CSIC Granada), G. García-Segura (Instituto de Astronomía de la UNAM, Ensenada), M. Gritsevich (Univ. of Helsinki), Y.-D. Hu (Guanxi Univ.), S. Góngora-García and J.-F.Agüí-Fernández (CAHA), on behalf of a larger collaboration, report:
We observed the location of EP250702a (Cheng et al., GCN 40906, 40917), associated with the four high-energy events GRB 250702B,C,D,E, all detected by Fermi/GBM (Fermi GBM Team, GCN 40883, 40885, 40886, 40890), Swift/BAT (GUANO system; DeLaunay et al., GCN 40903) and Konus/Wind (Frederiks et al., GCN 40914), with all these events likely originating from the same astrophysical source (Neights et al., GCN 40891).
Using the 2.2m CAHA telescope in Spain (equipped with CAFOS), we obtained 60s exposures in the z-band, starting on 2025 July 3 at 23.99 UT (i.e. 34.1 hr after the first Fermi trigger, GRB 250702B). At the location of the UVOT-enhanced position provided by Swift/XRT (Kennea et al., GCN 40919) and the VLT nIR source reported by Martin-Carrillo et al. (GCN 40924), we do not detect an optical source on the co-added z-band (1980s total exposure time) down to z = 21.4 (3-sigma limiting magnitude), using the Pan-STARRS1 DR2 (Magnier et al. 2025) catalogue as reference.
We thank the staff at CAHA for their excellent support.