GCN Circular 41044
Subject
GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
Event
Date
2025-07-09T03:22:13Z (9 hours ago)
From
Tomas Ahumada Mena at Caltech <tahumada@caltech.edu>
Via
Web form
Kaustav K. Das, Kritti Sharma, Viraj Karambelkar, Mansi Kasliwal, Tomas Ahumada (Caltech), Xander J. Hall (CMU) on behalf of the ZTF collaboration:
We used MOSFIRE on Keck I to image the afterglow candidate reported by Martin-Carrillo et al. (GCN 40924), likely associated with EP250702a (Cheng et al., GCNs 40906, 40917) and GRB 250702B, D, and E, detected by Fermi/GBM (Fermi GBM Team, GCNs 40883, 40886, 40890), Swift/BAT (via GUANO; DeLaunay et al., GCN 40903), and Konus/Wind (Frederiks et al., GCN 40914). Observations began at 2025-07-05T10:14:00 UTC and consisted of imaging in the J, H, and Ks bands.
We detect the afterglow candidate in the Ks band with m_K = 21.7±0.1 (AB). The source is not detected in the H and J bands, with limiting magnitudes of m_H > 22.4 (AB) and m_J > 22.8 (AB), respectively. These results are consistent with a temporal decay index of ~1.7 (Martin-Carrillo et al., GCN 40924; Levan et al., GCN 40961).
We thank the Keck Observatory staff for their support in facilitating these observations.