Report
Deciphering the extreme X-ray variability of the nuclear transient eRASSt J045650.3-203750: A likely repeating partial tidal disruption event
| العنوان: | Deciphering the extreme X-ray variability of the nuclear transient eRASSt J045650.3-203750: A likely repeating partial tidal disruption event |
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| المؤلفون: | Liu, Zhu, Malyali, A., Krumpe, M., Homan, D., Goodwin, A. J., Grotova, I., Kawka, A., Rau, A., Merloni, A., Anderson, G. E., Miller-Jones, J. C. A., Markowitz, A. G., Ciroi, S., Di Mille, F., Schramm, M., Tang, Shenli, Buckley, D. A. H., Gromadzki, M., Jin, Chichuan, Buchner, J. |
| المصدر: | A&A 669, A75 (2023) |
| سنة النشر: | 2022 |
| المجموعة: | Astrophysics |
| مصطلحات موضوعية: | Astrophysics - High Energy Astrophysical Phenomena |
| الوصف: | (Abridged) In this paper, we present the results of an exceptional repeating X-ray nuclear transient, eRASSt J045650.3-203750 (hereafter J0456-20), uncovered by SRG/eROSITA in a quiescent galaxy at redshift of z~0.077. The main results are: 1) J0456-20 cycles through four distinctive phases: an X-ray rising phase leading into an X-ray plateau phase which lasts for ~2 months. This is terminated by a rapid X-ray flux drop phase during which the X-ray flux can drastically drop by more than a factor of 100 within 1 week followed by an X-ray faint state for about two months before it starts the X-ray rising phase again; 2) the X-ray spectra are generally soft in the rising phase with a photon index >3.0, and become harder as the X-ray flux increases. There is evidence of a multi-colour disk with inner region temperature of $T_\text{in}=70$ eV at the beginning of the X-ray rising phase. The high quality XMM-Newton data suggest that a warm and hot corona could be responsible for the X-ray emission, through inverse Comptonisation of soft disk seed photons, during the plateau phase and at the bright end of the rising phase; 3) J0456-20 shows only moderate UV variability and no significant optical variability; 4) radio emission is only detected (as yet) in the X-ray plateau phase, and shows a rapid decline on a time-scale of 2 weeks. We conclude that J0456-20 is likely a repeating nuclear transient with a tentative recurrence time of ~223 days. We discuss several possibilities to explain J0456-20's observational properties, and currently favour a repeating partial tidal disruption event (TDE) as the most likely scenario. The long-term X-ray evolution is explained as a transition between a thermal disk-dominated soft state and a steep power-law state, implying that the corona can be formed within a few months and destroyed within a few weeks. Comment: 27 pages, 13 figures, published in A&A |
| نوع الوثيقة: | Working Paper |
| DOI: | 10.1051/0004-6361/202244805 |
| URL الوصول: | http://arxiv.org/abs/2208.12452 |
| رقم الانضمام: | edsarx.2208.12452 |
| قاعدة البيانات: | arXiv |
| DOI: | 10.1051/0004-6361/202244805 |
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