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 ultraluminous X-ray (ULX) source whose X-ray-powering mechanism and bubblelike structure surrounding the source are topics of intense study. Here, we perform an X-ray spectroscopic study of the source using joint XMM-Newton and 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 disk mass accretion rate varies from 4.6 to 9.6 M Edd and the halo mass accretion rate varies from 4.0 to 6.1 M Edd with a dynamic Comptonizing corona of average size of ∼15 rg. 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 masses, with the most probable mass of the compact object being 133 ± 33 Me. 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 accordance with the observed optical bubble and winds found through high-resolution X-ray spectroscopy, suggesting that the bubble was 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 the jet/outflow is taken into account, in agreement with numerical simulations in the literature