EP-WXT detection of a possible new outburst from the HMXB IGR J20155+3827
ATel #16730; X. Mao, Q. Y. Wu, J. W. Hu, H. W. Pan, C. C. Jin, Z. X. Ling, Y. Liu, W. Yuan, C. Zhang, W. Chen, H. Q. Cheng, C. Z. Cui, D. W. Fan, H. B. Hu, M. H. Huang, H. Y. Liu, D. Y. Li, M. J. Liu, Z. Z. Lv, T. Y. Lian, X. Pan, 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), Y. Chen, S. M. Jia, S. N. Zhang (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.
on 22 Jul 2024; 14:36 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Yuan Liu (liuyuan@bao.ac.cn)
Subjects: X-ray, Transient
We report on the detection of a possible new outburst from the High Mass X-ray Binary IGR J20155+3827 by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The position of the source is R.A. = 303.857 deg, DEC = 38.427 deg (J2000) with an uncertainty of 2.1 arcmin in radius (90% C.L. statistical and systematic), which is 97 arcsec from the HMXB IGR J20155+3827, indicating the possible association between the two. The unabsorbed flux in 0.2-12 keV of this HMXB was estimated to be 3.55(+/-1.80)x10^-13 erg/s/cm^2 detected by XMM-Newton on 2017-05-01 (Onori et al. 2021, MNRAS). EP-WXT detected the source first in an observation starting at 2024-07-21T17:14:15 (UTC) and subsequently in several other observations in the following ~9 hours. Detailed spectral analysis shows an increase of the absorbed 0.5-4 keV flux of the source with time, from 7.2(+1.2/-1.0)x10^-11 erg/s/cm^2 to 1.0(+0.3/-0.2)x10^-10 erg/s/cm^2 in the latest observation. The WXT energy spectra are fitted by an absorbed powerlaw, with a photon index of ~4.0-5.4 (with large uncertainties) and a neutral hydrogen column density fixed at the Galactic value of 1.1x10^22 cm^-2. A follow-up observation with the Follow-up X-ray Telescope (FXT) on board EP is planned. Further 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). EP is a mission of the Chinese Academy of Sciences in collaboration with ESA, MPE and CNES.
