National conference on REcent Trends in the study of Compact Objects (RETCO-V): Theory and Observation

A stellar mass ULX NGC 6946 X-1 and its super-Eddington accretion

Apr 5, 2023, 12:30 PM

15m

Auditorium (Kodaikanal Solar Observatory)

ULX Sources ULX Sources

Speaker

Tanuman Ghosh (Raman Research Institute)

Description

Ultraluminous X-ray sources (ULXs) are the brightest known non-nuclear X-ray binaries with luminosities exceeding the classical Eddington limit of a 10 ${\mathrm{M}}_{\odot }$ black hole. Recent discoveries of neutron star cores in ULXs confirm that the Eddington ratio can be a few hundred. Broadband spectral studies are pivotal to deciphering the emission mechanism in these mysterious sources. Here we discuss the accretion mechanism in a soft ultraluminous X-ray source NGC 6946 X-1. The broadband X-ray spectra of this source show quasi-steady nature in different epochs of observation. Two thermal emission components primarily govern the continuum. One originates from the inner accretion flow from a slim accretion disk, and the other is associated with an optically thick wind due to super-critical accretion. We also discuss some physical properties of the source based on the assumption of a realistic inclination angle of the accretion disk. The implication of a low massive black hole ($\sim 6-10{\mathrm{M}}_{\odot }$) or a neutron star of weak magnetic field ($\mathrm{B}\le 2\times {10}^{11}$ G) confirms the super-Eddington accreting nature of this source.