Massive black holes and tidal disruption events at the center of galaxies

When a star enters the tidal radius of a massive black hole (BH) at the center of a galaxy, the tidal force will rip the star apart. The BH may accrete the debris of the star and produce energetic flare. This phenomenon is now commonly known as Tidal Disruption Event (TDE). The characteristics of its spectra as well as variability are dependent on the properties of the central BH and the disrupted star, so that we can study their parameters, accretion process and jet, and the property of circumnuclear environment by confirming and systematically studying the BH in quiescent galaxies. TDE may also provide important clues on the existence of intermediate BH as well as supermassive BH binary. However, the study of TDE is hindered by relatively small sample size (especially in X-ray band) and low quality of data due to the low incident rate. The Einstein Probe (EP), which covers the 0.5-4 keV soft X-ray energy band, has a large field of view as well as high sensitivity, making it perfect to detect TDE. We expect that EP will detect several tens to about one hundred TDE every year, of which around 10 or even more are TDE with relativistic jet. This will result in a homogeneously selected completely TDE sample, which is important for investigating the statistical property of TDE. It makes it possible to investigate the existence and statistical property of BH, explore the growth and evolution of BH, discovery the intermediate BH as well as supermassive BH binaries.