Einstein Probe detection of a new bright outburst from GRS 1739-278
ATel #17377; Y. H. Cheng (SWIFAR, YNU), C. Zhou (HUST), S. L. Wang (YNU), T. Y. Liu, H. Q. Cheng, C. C. Jin (NAO, CAS)
on 8 Sep 2025; 09:33 UT
Credential Certification: Yuan Liu (liuyuan@bao.ac.cn)
Subjects: X-ray, Binary, Black Hole
We report on the detection of a new bright X-ray outburst from the black hole low-mass X-ray binary candidate GRS 1739-278, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. A previous outburst of GRS 1739-278 was observed from mid June to mid August 2025 (ATel #17238), with the peak flux of ~1e-9 erg/s/cm^2. Later the source went into a new, brighter outburst. The spectrum of the latest WXT observation (started on 2025-09-07T22:45:57 UTC) can be generally fitted by an absorbed multi-color disk blackbody model (tbabs*diskbb), with a neutral hydrogen column density of 1.7(+/-0.05) x 10^22 cm^-2 and temperature of the inner radius of 0.92(+/-0.03) keV. The derived observed flux in 0.5-4 keV is 4.0(+/-0.9) x 10^-9 erg/s/cm^2.
Multi-wavelength follow-up observations are encouraged.
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).
