Estimating the black hole mass of NGC1313 X-1 based on the spectral and timing properties

The discovery of 3:2 quasi-periodic oscillations (QPOs) in the ultraluminous X-ray source NGC 1313 X-1 suggests it harbors an intermediate-mass black hole (IMBH). We test this numerically by modelling the 3:2 QPOs and the associated X-ray spectrum based on the epicyclic resonance model and a disk-corona model with large-scale magnetic fields generated by the Cosmic Battery mechanism. The combined QPO-frequency and spectral fitting indicates that the BH mass ranges from 2524M_sun to 6811M_sun confirming its IMBH nature, and the BH spin is probably higher than ~0.3.