Einstein Probe detection of a new outburst from XTE 1739-285
ATel #17727; Q. C. Zhao (IHEP), Z. H. Yang (IHEP), R. D. Liang (NAO, CAS), H. Sun(NAO, CAS), B. T. Wang (YNAO, CAS), X. H. Tang (Tsinghua University), Z. M. Wang (CAS) on behalf of the Einstein Probe team
on 26 Mar 2026; 07:47 UT
Credential Certification: Yuan Liu (liuyuan@bao.ac.cn)
Subjects: X-ray, Binary, Transient
We report the detection of a new outburst from XTE J1739-285 with the Wide-field X-ray Telescope (WXT) onboard the Einstein Probe (EP). The source was discovered in 1999 (Martkwardt et al. 1999) and has exhibited multiple outbursts since then. Most recently, the source underwent an outburst in 2023 (ATel #15927). EP/WXT first detected the current outburst on 2026 March 15, with a flux of about 4.2 Ã 10-11 erg cm-2 s-1. Since then, the source flux has continued to rise. The latest WXT spectrum can be fitted with an absorbed power-law model, with a photon index of 2.7 +/- 0.5. The current unabsorbed flux in 0.5-4 keV is 9.2(+6.7,-3.3) Ã 10-9 erg cm-2 s-1 (68% confidence level). Further follow-up observations are encouraged.
Launched on January 9, 2024, EP is a space X-ray observatory designed to monitor the soft X-ray sky with rapid 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.
