The X-ray source 2XMM J123103.2+110648 was previously found to show pure thermal X-ray spectra and a \sim 3.8 hr periodicity in three XMM-Newton X-ray observations in 2003–2005 , and the optical spectrum of the host galaxy suggested it as a type 2 active galactic nucleus candidate .
We have obtained new X-ray observations of the source , with Swift and Chandra in 2013–2016 , in order to shed new light on its nature based on its long-term evolution property .
We found that the source could be in an X-ray outburst , with the X-ray flux decreasing by an order of magnitude in the Swift and Chandra observations , compared with the XMM-Newton observations ten years ago .
There seemed to be significant spectral softening associated with the drop of X-ray flux ( disk temperature kT \sim 0.16 –0.2 keV in XMM-Newton observations versus kT \sim 0.09 \pm 0.02 keV in the Chandra observation ) .
Therefore the Swift and Chandra follow-up observations support our previous suggestion that the source could be a tidal disruption event ( TDE ) , though it seems to evolve slower than most of the other TDE candidates .
The apparent long duration of this event could be due to the presence of a long super-Eddington accretion phase and/or slow circularization .