Properties of the black hole candidate XTE J1118+480 with the TCAF solution during its jet activity induced 2000 outburst

The galactic black hole candidate (BHC) XTE J1118+480 during its 2000 outburst has been studied in a broad energy range using the archival data of PCA and HEXTE payloads of Rossi X-ray Timing Explorer. Detailed spectral and temporal properties of the source are studied. Low and very low frequency quasi-periodic oscillations (QPOs), with a general trend of increasing frequency are observed during the outburst. Spectral analysis is done using the combined data of the PCA and HEXTE instruments with two types of models: the well-known phenomenological power-law model and the current version of the fits file of two-component advective flow (TCAF) solution as an additive table model in XSPEC. During the entire period of the outburst, a non-thermal power-law component and the TCAF model fitted to the sub-Keplerian halo rate were found to be highly dominant. We suggest that this so-called outburst is due to enhanced jet activity. Indeed, the ‘outburst’ subsides when this activity disappears. We estimated the X-ray fluxes coming from the base of the jet and found that the radio flux is correlated with this X-ray flux. Though the object was in the hard state in the entire episode, the spectrum becomes slightly softer with the rise in the Keplerian disk rate in the late declining phase. We also estimated the probable mass of the source from our spectral analysis with the TCAF solution. Our estimated mass of XTE J1118+480 is 6.99−0.74+0.50M⊙$6.99^{+0.50}_{-0.74}~M_{\odot }$ i.e., in the range of 6.25–7.49M⊙$7.49~M _{\odot }$.