TITLE: GCN CIRCULAR NUMBER: 41021 SUBJECT: IceCube-250706A: EP-FXT follow-up observations DATE: 25/07/08 09:58:11 GMT FROM: EP Team at NAOC/CAS <ep_ta@bao.ac.cn> Q. Y. Wu, Y. Liu (NAO, CAS), G. Giulia, A. L. Thakur (INAF-IAPS) on behalf of the Einstein Probe (EP) team: EP-FXT performed two follow-up observations of the IceCube-250706A (GCN 40994) (goldtrack) event. The first follow-up observation (obs1) started from 2025-07-06T13:56:24, about 40 minutes after the neutrino trigger, with an exposure time of 5.9 ks. The second one (obs2) started from 2025-07-06T21:01:14, about 8 hours after the trigger, with an exposure time of 4.1 ks. With the 1 deg x 1 deg FoV, EP-FXT covered most part of the 90% C.L. error region of the neutrino event. Within the neutrino localization error region, only one source exhibited significant variability compared with historical fluxes or historical upper limits. The details are listed below: Source: EPF_J174217.4+392257 RA (J2000): 265.5726 Dec (J2000): 39.3826 Position error in radius: 10 arcsec (90% C.L.) Flux in obs1: 1 x 10^-12 erg/s/cm2 (0.5-10 keV) Flux in obs2: not detected, with an upper limit around 5 x 10^-14 erg/s/cm2 (0.5-10 keV) A BY Dra variable star, ZTF J174217.39+392252.1, is 5 arcsec away from EPF_J174217.4+392257. Thus, the significant variability is likely due to the flare of this star with the X-ray luminosity of 6 x 10^30 erg/s. No other source exhibited significant variability between the two observations. 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). View this GCN Circular online at https://gcn.nasa.gov/circulars/41021. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...