GCN Circular 36894

IceCube-Cascade 240714A: X-ray follow-up observation with EP-FXT

H. Zhou (PMO), M. J. Liu, X. Pan (NAOC, CAS), Y. C. Fu (BNU), H. W. Pan, Z. X. Ling, C. C. Jin, W. Yuan, Y. Liu, C. Zhang, W. Chen, H. Q. Cheng, C. Z. Cui, D. W. Fan, H. B. Hu, J. W. Hu, M. H. Huang, D. Y. Li, H. Y. Liu, Z. Z. Lv, T. Y. Lian, X. Mao, H. Sun, W. X. Wang, Y. L. Wang, S. X. Wen, Q. Y. Wu, X. P. Xu, Y. F. Xu, H. N. Yang, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), J. Guan, C. K. Li, Y. Chen, S. M. Jia, W. W. Cui, H. Feng, D. W. Han, W. Li, C. Z. Liu, F. J. Lu, L. M. Song, J. Wang, J. J. Xu, J. Zhang, S. N. Zhang, H. S. Zhao, X. F. Zhao (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team


We performed an observation of IceCube-Cascade 240714A (ATEL #16708) with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission. The observation began at 2024-07-16T08:46:36 (UTC), and the exposure time is about 8.4 ks. FXT-A and FXT-B detected 2 sources in the 90% localization error circle (with a radius of 0.3 deg centered on RA, DEC = 243.28, -36.61), and one of them (EP J161324.4-363745) is uncatalogued. The following table lists all sources detected by the FXT (field of view ~ 1 deg x 1 deg), and sources located in the 90% localization error circle are marked. The positions are given with an uncertainty of 30 arcsec (radius, 90% C.L. statistical and systematic). The 0.5 - 10 keV flux is derived from FXT-A data.

Source |   R.A.  |   Dec.  | FXT-A Significance | FXT-B Significance | Estimated Flux | eROSITA Flux (0.2-2.3 keV)
       | (J2000) | (J2000) |                    |                    |  (erg/s/cm^2)  |       (erg/s/cm^2)
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EP J161324.4-363745* | 243.3527 | -36.6283 | 7.7  | 4.0  | 7.2 x 10^-14 | uncatalogued
EP J161423.8-362537* | 243.6011 | -36.4259 | 6.2  | 8.0  | 1.0 x 10^-13 | 7.07 x 10^-14
EP J161307.1-365708  | 243.2801 | -36.9508 | 8.7  | 11.2 | 2.3 x 10^-13 | uncatalogued
EP J161439.0-362654  | 243.6603 | -36.4492 | 10.3 | 8.7  | 1.7 x 10^-13 | 1.07 x 10^-13
EP J161357.7-361806  | 243.4905 | -36.3016 | 51.0 | 53.1 | 7.6 x 10^-13 | 9.12 x 10^-13
EP J161128.2-361818  | 242.8680 | -36.3074 | 7.2  | 6.7  | 1.3 x 10^-13 | 1.39 x 10^-13
EP J161433.2-365843  | 243.6389 | -36.9785 | 15.0 | 14.9 | 3.7 x 10^-13 | 3.40 x 10^-13
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*Note: These sources are located in the 90% localization error circle of IceCube-Cascade 240714A.

The above observation was made with the EP-FXT instrument. 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). EP is a mission of the Chinese Academy of Sciences in collaboration with ESA, MPE and CNES.