Abstract Details

Name: Tushar Mondal
Affiliation: Indian Institute of Science (IISc)
Conference ID: ASI2020_394
Title : Ultra-luminous X-ray sources as magnetically powered advective flows around black holes
Authors and Co-Authors : Tushar Mondal and Banibrata Mukhopadhyay
Abstract Type : Oral
Abstract Category : Extragalactic Astronomy
Abstract : Ultra-luminous X-ray sources (ULXs) are very bright, off-nuclear, point sources with luminosity exceeding the standard Eddington limit of a stellar-mass black hole (BH). The physical scenarios to explain their unusual large apparent luminosity are either super-Eddington accretion around a stellar-mass BH, or the existence of the missing class of intermediate mass BH (IMBH), or beamed emission. However, the supporting evidences for IMBH scenario has been disputed extensively. Most ULXs with steep power-law spectrum can be well explained by super-Eddington accretion phenomena. Nevertheless, the interpretation of a significant fraction of ULXs with hard spectral states remains mysterious. I have suggested, for the first time, that hard-state ULXs are magnetically dominated, advective, sub-Eddington mass (but super-Eddington magnetic at outer zone) accretion flows around stellar-mass BHs, and neither need to incorporate the existence of the missing class of IMBHs, nor super-Eddington accretion phenomenon. In order to achieve such large luminosity, the magnetic field of the advective flow has to be larger than the corresponding Eddington magnetic field. References: [1] Mondal T., Mukhopadhyay B., submitted, arXiv:1910.08564 [2] Mondal T., Mukhopadhyay B., MNRAS Letters, 482, L24 (2019) [3] Mondal T., Mukhopadhyay B., MNRAS, 476, 2396 (2018)