| Abstract : | Ultraluminous X-ray sources (ULXs) are the brightest X-ray binaries (XRBs), emission luminosity of which exceeds the Eddington limit of a ten solar mass black hole. Recent consensus is that majority of these sources host stellar-mass super-Eddington accretors as their central powerhouse. However, the interpretation of intermediate-mass black hole accretors can not be turned down in a few cases. A comparison between ULX accretion states and Galactic XRB accretion states will be discussed. Many of the ULXs show strong spectral and timing variability. Hence, these objects have a substantial prospect in studying X-ray transients. Especially, flaring events which are very common in XRBs, are seen intermittently in ULXs. Hence, such flaring ULX sources need special attention. A modern perspective on the generalized picture of accretion physics in ULXs will be discussed, along with a few case studies of individual ULXs. |
