Einstein Probe Discovery of EP J005245.1−722843: A Rare Be–White Dwarf Binary in the Small Magellanic Cloud?

Abstract On 2024 May 27, the Wide-field X-ray Telescope on board the Space Sciences, University of Chinese Academy of Einstein Probe (EP) mission detected enhanced X-ray emission from a new transient source in the Small Magellanic Cloud during its commissioning phase. Prompt follow-up with the EP Follow-up X-ray Telescope, the Swift X-ray Telescope. and NICER have revealed a very soft, thermally emitting source ( kT ~ 0.1 keV at the outburst peak) with an X-ray luminosity of L ~ 4 × 10 38 erg s −1 , labeled EP J005245.1−722843. This supersoft outburst faded very quickly in a week's time. Several emission lines and absorption edges were present in the X-ray spectrum, including deep nitrogen (0.67 keV) and oxygen (0.87 keV) absorption edges. The X-ray emission resembles the supersoft source phase of typical nova outbursts from an accreting white dwarf (WD) in a binary system, despite the X-ray source being historically associated with an O9-B0e massive star exhibiting a 17.55 day periodicity in the optical band. The discovery of this supersoft outburst suggests that EP J005245.1−722843 is a BeWD X-ray binary: an elusive evolutionary stage where two main-sequence massive stars have undergone a common envelope phase and experienced at least two episodes of mass transfer. In addition, the very short duration of the outburst and the presence of Ne features hint at a rather massive, i.e., close to the Chandrasekhar limit, Ne–O WD in the system.

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Publication Details

Journal
The Astrophysical Journal Letters
Published
2025-02-18
DOI
https://doi.org/10.3847/2041-8213/ad9580
Citations
16
Primary Topic
Stellar, planetary, and galactic studies
Type
article
Field-Weighted Citation Impact
18.48

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article

Einstein Probe Discovery of EP J005245.1−722843: A Rare Be–White Dwarf Binary in the Small Magellanic Cloud?

N. Rea, E. P. J. van den Heuvel, S. M. Jia, H. Feng et al.
16 citations
The Astrophysical Journal Letters
Stellar, planetary, and galactic studies
18.48
article

Einstein Probe Discovery of EP J005245.1−722843: A Rare Be–White Dwarf Binary in the Small Magellanic Cloud?

N. Rea, E. P. J. van den Heuvel, S. M. Jia, H. Feng, F. Coti Zelati, A. Marino, Roberto Soria, Chandreyee Maitra, Chichuan Jin, Weimin Yuan, Yong Chen, Dongyue Li, E. Kuulkers, Gaurava K. Jaisawal, Lian Tao, Haiyang Cheng, W. Chen, Sébastien Guillot, Shanshan Weng, Jan‐Uwe Ness, Hui Sun, Mason Ng, Tod E. Strohmayer, Haonan Yang, Chongjie Zhang, F. Haberl, Z. X. Ling, Xin Pan, Keith C. Gendreau, Long Ji, Bing Zhang, Wenda Zhang, Guobao Zhang, Zhipeng Lv, Yang Liu
article en
16 citations

Abstract

Abstract On 2024 May 27, the Wide-field X-ray Telescope on board the Space Sciences, University of Chinese Academy of Einstein Probe (EP) mission detected enhanced X-ray emission from a new transient source in the Small Magellanic Cloud during its commissioning phase. Prompt follow-up with the EP Follow-up X-ray Telescope, the Swift X-ray Telescope. and NICER have revealed a very soft, thermally emitting source ( kT ~ 0.1 keV at the outburst peak) with an X-ray luminosity of L ~ 4 × 10 38 erg s −1 , labeled EP J005245.1−722843. This supersoft outburst faded very quickly in a week's time. Several emission lines and absorption edges were present in the X-ray spectrum, including deep nitrogen (0.67 keV) and oxygen (0.87 keV) absorption edges. The X-ray emission resembles the supersoft source phase of typical nova outbursts from an accreting white dwarf (WD) in a binary system, despite the X-ray source being historically associated with an O9-B0e massive star exhibiting a 17.55 day periodicity in the optical band. The discovery of this supersoft outburst suggests that EP J005245.1−722843 is a BeWD X-ray binary: an elusive evolutionary stage where two main-sequence massive stars have undergone a common envelope phase and experienced at least two episodes of mass transfer. In addition, the very short duration of the outburst and the presence of Ne features hint at a rather massive, i.e., close to the Chandrasekhar limit, Ne–O WD in the system.

The Astrophysical Journal LettersVol. 980(2)
Technical University of Denmark (DK)
National Aeronautics and Space Administration, University of Leicester, European Commission, National Natural Science Foundation of China, Chinese Academy of Sciences, Centre National d’Etudes Spatiales, China Scholarship Council, Youth Innovation Promotion Association of the Chinese Academy of Sciences, Centers for Disease Control and Prevention, Youth Innovation Promotion Association
Openalex Percentile: Top 1%
Stellar, planetary, and galactic studies
18.48
DOIOpen Access PDFOpenAlex
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