Oral Presentation

X-ray luminosity function of tidal disruption events from MAXI extragalactic survey

Taiki Kawamuro, Yoshihiro Ueda, Megumi Shidatsu, Takafumi Hori (Kyoto University), Nobuyuki Kawai (Tokyo Institute of Technology) and MAXI team

The nature of supermassive black holes (SMBHs) that reside in "inactive" galaxy nuclei is difficult to explore. However, when the orbital path of a star becomes close enough to a dormant SMBH to be disrupted by the tidal force exceeding the self-gravity of the star, a luminous flare in the UV/X-ray bands is expected, called a tidal disruption event (TDE). Here we report the first X-ray luminosity function of TDEs from an unbiased sample observed by the Monitor of All-sky X-ray Image (MAXI), which is in operation since 2009. A systematic search using the MAXI data in the first 37 months detected three TDEs. To derive the luminosity function, we perform unbinned maximum likelihood fit to these events with a Schechter-type function, taking into account the fraction of TDEs with relativistic jets. The predicted TDE rates from the best-fit model are in agreement with the previous study by ROSAT (Donley et al. 2002). Our results indicate that the contamination by TDEs to the hard X-ray luminosity function of active galactic nuclei is not significant and that their contribution to the growth of SMBHs is negligible at redshifts lower than 1.5.