Broadband X-ray spectral analysis of the ULX NGC 1313\,X-1 using JeTCAF: Origin of the ULX bubble

Abstract

NGC 1313\,X-1 is a mysterious Ultra-luminous X-ray (ULX) source whose X-ray powering mechanism and a bubble-like structure surrounding the source are topics of intense study. Here, we perform the X-ray spectroscopic study of the source using a joint {\it XMM-Newton} and {\it NuSTAR} observations taken during 2012 $-$ 2017. The combined spectra cover the energy band 0.3 $-$ 20 keV. We use the accretion-ejection-based JeTCAF model for spectral analysis. The model fitted disc mass accretion rate varies from 4.6 to 9.6 $\dot M_{\rm Edd}$ and the halo mass accretion rate varies from 4.0 to 6.1 $\dot M_{\rm Edd}$ with a dynamic Comptonizing corona of average size of $\sim 15$ $r_g$. The data fitting is carried out for different black hole (BH) mass values. The goodness of the fit and uncertainties in model parameters improve while using higher BH mass with most probable mass of the compact object to be $133\pm33$ M$_\odot$. We have estimated the mass outflow rate, its velocity and power, and the age of the inflated bubble surrounding the source. Our estimated bubble morphology is in accord with the observed optical bubble and winds found through high-resolution X-ray spectroscopy, suggesting that the bubble expanded by the outflows originating from the central source. Finally, we conclude that the super-Eddington accretion onto a nearly intermediate mass BH may power a ULX when the accretion efficiency is low, though their efficiency increases when jet/outflow is taken into account, in agreement with numerical simulations in the literature.