GCN Circular 40967
Subject
GRB250702F: afterglow detected by joint EP-ZTF shadowing program
Event
Date
2025-07-05T06:48:13Z (2 days ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
R. D. Liang, D.Y. Li, H. Q. Cheng, Z. X. Ling (NAO, CAS), Y. J. Zhang (THU), C. Zhou (HUST), G. Y. Zhao (SYSU), A. Li (BNU), Y. H. Cheng (SWIFAR, YNU), C. C. Jin, and W. M. Yuan (NAO, CAS), Robert Stein (UMD), Tomas Ahumada (Caltech), Mansi Kasliwal(Caltech), Theophile du Laz (Caltech), and Lin Yan (Caltech) on behalf of the Einstein Probe (EP) team and the Zwicky Transient Facility Partnership:
We report on the joint identification of the afterglow of GRB 250702F (Swift/BAT detection, GCN 40894; Fermi/GBM detection, GCN 40892) by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission and ZTF through the EP-ZTF shadowing program (Ahumada et al., GCN 39791). The EP-WXT observation started at 2025-07-02 21:41:26 (UTC), about 2ks after Swift/BAT detection. The WXT position of the source is R.A. = 212.899 deg, DEC = 16.74 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic), which is consistent with the optical counterpart (ZTF25aazgntl/AT2025qdw, TNS#183358; Klingler et al., GCN 40894; Jelinek et al., GCN 40895; Kumar et al., GCN 40896; Lipunov et al., GCN 40899; Martin-Carrillo et al. GCN 40900; de Ugarte Postigo et al. GCN 40901; Angulo et al. GCN 40907; Becerra et al. GCN 40911; Brivio et al. GCN 40913; An et al. GCN 40916; Odeh et al. GCN 40925; Moretti et al. GCN 40926) and the X-ray counterpart (Swift/XRT team, GCN 40902, GCN 40928).
The WXT spectrum can be fitted with an absorbed power law model with fixed column density of 1.34e20 cm^-2, a photon index of 2.06+/-0.71, and an unabsorbed 0.5-4 keV flux of (5.13+/-0.81)e-11 erg/s/cm^2, which is consistent with Swift/XRT analysis (Swift/XRT team, GCN 40928).
The contact transient advocate of this source is Runduo Liang (liangrd@bao.ac.cn). Please contact him for coordination of multi-wavelength follow-up observations and access to EP-WXT data.
Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).