Volume 652, August 2021
|Number of page(s)||7|
|Published online||03 August 2021|
Long-term X-ray evolution of SDSS J134244.4+053056.1
A more than 18 year-old, long-lived IMBH-TDE candidate
Department of Astronomy, Guangzhou University, Guangzhou 510006, PR China
2 College of Engineering Physics, Shenzhen Technology University, Shenzhen 518118, PR China
3 Department of Physics, Anhui Normal University, Wuhu, Anhui 241000, PR China
4 CAS Key Laboratory for Researches in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei, Anhui 230026, PR China
5 School of Physics and Astronomy, Sun Yat-Sen University, Zhuhai 519082, PR China
6 Shenzhen Key Laboratory of Ultraintense Laser and Advanced Material Technology, Shenzhen 518118, PR China
Accepted: 21 May 2021
SDSS J134244.4+053056 is a tidal disruption event candidate with strong temporal coronal line emitters and a long fading, mid-infrared dust echo. We present detailed analyses of X-ray emission from a Swift/XRT observation in 2009 and the most recent XMM-Newton/pn observation in 2020. The two spectra can be modeled with hard and soft components. While no significant variability is detected in the hard component above 2 keV between these two observations, the soft X-ray emission in 0.3–2 keV varies by a factor of ∼5. The luminosity of this soft component fades from ∼1.8 × 1041 to ∼3.7 × 1040 erg s−1 from the observation in Swift to that of XMM-Newton, which are 8 and 19 years after the outburst occurred, respectively. The evolution of luminosity matches with the t−5/3decline law well; there is a soft X-ray peak luminosity of 1044 erg s−1 at the time of the optical flare. Furthermore, the spectra of the soft component harden slightly in the decay phase, in which the photon index Γ varies from 4.8−0.9+1.2 to 3.7 ± 0.5, although they are consistent with each other if we consider the uncertainties. Additionally, by comparing the BH mass estimate between the M − σ correlation, the broad Hα emission, and the fundamental plane relation of BH accretion, we find that a value of ∼105 M⊙ is favored. If so, taking its X-ray spectral variation, luminosity evolution, and further support from theory into account, we suggest that SDSS J134244.4+053056 is a long-lived tidal disruption event candidate lasting more than 18 years with an intermediate-mass black hole.
Key words: accretion, accretion disks / black hole physics / X-rays: galaxies / galaxies: individual: SDSS J134244.4+053056.1
© ESO 2021
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