Is there an intermediate massive black hole in the Galactic center: Imprints on the stellar tidal-disruption rate

Abstract: It has been suggested that an intermediate-massive black hole (IMBH) with mass $10^{3-5} M_\odot$ could fall into the galactic center (GC) and form a massive black hole binary (MBHB) with the central supermassive black hole, but current observations are not sensitive to constrain all mass and distance ranges. Motivated by the recent discovery that MBHBs could enhance the rate of tidal-disruption events (TDEs) of stellar objects, we investigate the prospect of using stellar-disruption rate to probe IMBHs in the GC. We incorporated the perturbation by an IMBH into the loss-cone theory and calculated the stellar-disruption rates in the GC. We found that an IMBH heavier than $2000 M_\odot$ could distinguishably enhance the stellar-disruption rate. By comparing observations of Sgr A* with the fall-back model for stellar debris, we suggested that the TDE rate in our Galaxy should not significantly exceed $0.002 yr^{-1}$, therefore a fraction of the parameter space for the IMBH, concentrating at the high-mass end, can already be excluded. To derive constraint in the remaining parameter space, it is crucial to observationally confirm or reject the stellar-disruption rate between $10^{-4}$ and $10^{-2} yr^{-1}$, and we discussed possible strategies to make such measurements.