Properties of Faint X-ray Activity of XTE J1908+094 in 2019

Abstract

We study the properties of the faint X-ray activity of Galactic transient black hole candidate XTE J1908+094 during its 2019 outburst. Here, we report the results of detailed spectral and temporal analysis during this outburst using observations from Nuclear Spectroscopic Telescope Array (NuSTAR). We have not observed any quasi-periodic-oscillations (QPOs) in the power density spectrum (PDS). The spectral study suggests that the source remained in the softer (more precisely, in the soft–intermediate) spectral state during this short period of X-ray activity. We notice a faint but broad Fe Kα emission line at around 6.5 keV. We also estimate the probable mass of the black hole to be 6.5−0.7+0.5M⊙, with 90% confidence.

Accretion Flow Properties of GRS 1716-249 during its 2016-17 'failed' Outburst

“…An outburst is generally considered to be triggered, when rise in viscosity at the outer-edge of the disk occurs (Chakrabarti 1996;Ebisawa et al 1996). According to Chakrabarti and his collaborators (Chakrabarti et al 2019;Bhowmick et al 2020), accreted matter from the companion first piles up at the far location (within Lagrange point L1), known as the pile-up radius (X p ) inside the Roche lobe. Due to the accumulation of large amount of matter at X p , viscosity rises and crosses its critical value to trigger an outburst.…”

“…In general, at the beginning of an outburst, we see high dominance of the PL component. When an outburst is triggered due to a sudden rise in viscosity at the pile up radius i.e., at the outer disk, both types of matter start to move towards the BH after forming accretion disk (Ebisawa et al 1996;Chakrabarti et al 2019). As discussed before, being low viscous and low angular momentum, the sub-Keplerian matter moves closer to the BH much faster (roughly in a free fall time) than Keplerian component (moves in viscous time), and dominates at the beginning of an outburst.…”

“…are present. Recently, after its (TCAF) inclusion as an additive table model in XSPEC (Debnath et al 2014(Debnath et al , 2015a, spectra of many BHC have been successfully fitted and described by our group (Debnath et al 2015a(Debnath et al ,b,2017(Debnath et al ,2020Mondal et al 2014Mondal et al , 2016Chatterjee et al 2016Chatterjee et al ,2019Jana et al 2016Jana et al ,2020aChatterjee et al 2020, Shang et al 2019. Estimation of mass of these sources has also been done using the TCAF model.…”

Similarities and Differences in Accretion Flow Properties between GRS 1915+105 and IGR J17091-3624: a Case Study

“…Prior to the launch of RXTE, the TCAF model which incorporates the high angular momentum Keplerian flow and low angular momentum sub-Keplerian flow in the same framework (Chakrabarti 1995(Chakrabarti , 1997 was proposed for both Galactic and extragalactic black holes. This model has been successfully applied to explain the observed spectral features of transient X-ray sources and infer the underlying accretion flow dynamics (Debnath et al 2014(Debnath et al , 2015a(Debnath et al ,b, 2017(Debnath et al , 2020Mondal et al 2014Mondal et al , 2016Jana et al 2016Jana et al , 2017Jana et al , 2020Molla et al 2016Molla et al , 2017Chatterjee et al 2016Chatterjee et al , 2019Chatterjee et al , 2020. Recently, the TCAF paradigm has been successfully applied to model the spectro-temporal characteristics of weakly magnetized neutron stars as well after incorporating the modifications corresponding to the inner boundary , 2018, 2021.…”

Accretion Flow Properties of XTE J1118+480 During Its 2005 Outburst

“…This is suggested to be a high inclined (∼ 68 − 79 • ) (Khargharia et al 2013), short orbital period (∼ 4.1 hrs) (Patterson et al 2000;Gonzalez Hernandez et al 2012) low mass binary system. The spectral and the temporal properties of the source during its 2000 outburst have been studied by Chatterjee et al (2019; hereafter Paper-I), using RXTE PCA and HEXTE combined data with the physical two component advective flow (TCAF) model (Chakrabarti & Titarchuk 1995) to understand the accretion flow dynamics of the source. Estimation of X-ray contribution of the jet made from spectral analysis with the TCAF model suggests that the outburst was dominated by the jets/outflows.…”