| Name: | Tanuman Ghosh |
| Affiliation: | Inter-University Centre for Astronomy and Astrophysics |
| Conference ID : | ASI2024_732 |
| Title : | Nature of accretion in ULXs |
| Authors : | Tanuman Ghosh 1, Vikram Rana 2 |
| Authors Affiliation: | 1 Inter-University Centre for Astronomy and Astrophysics, Pune 411007, India
2 Raman Research Institute, Bangalore 560080, India |
| Mode of Presentation: | Oral |
| Abstract Category : | High Energy Phenomena, Fundamental Physics and Astronomy |
| Abstract : | Ultraluminous X-ray sources (ULXs) are non-nuclear X-ray binaries with X-ray luminosities exceeding the Eddington limit of a 10 solar mass black hole. Initial perception was that intermediate-mass black holes are the powerhouse of such high luminosities. However, the discovery of neutron stars and broadband X-ray studies of most ULXs indicate that super-Eddington accretion onto stellar-mass compact objects is the physical origin of such high power. We discuss the analysis of a sample of sources with varying spectral hardness in the purview of their accretion mechanism. A detailed broadband study of a soft ULX, NGC 6946 X-1, shows a quasi-steady nature in different observation epochs, which helps us constrain its accretion flow. The continuum is governed by two-component thermal emission from a hot, slim accretion disk, and a cool component comes from the optically thick wind, which also shows emission/absorption line features. Our analysis finds that the source is either a stellar-mass black hole or a moderately magnetized neutron star with a high accretion rate. In this line of interpretation, several other sources, ranging from supersoft to hard sources, are also found to be stellar-mass super-Eddington accretors. |
