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

• Main Authors: Debjit Chatterjee, Arghajit Jana, Kaushik Chatterjee, Riya Bhowmick, Sujoy Kumar Nath, Sandip K. Chakrabarti, A. Mangalam, Dipak Debnath
• Format: Article
• Language: English
• Published: MDPI AG 2021-04-01
• Series: Galaxies
• Subjects: X-Rays:binaries—stars individual: (XTE J1908+094)—stars:black holes—accretion; accretion disks—shock waves—radiation:dynamics
• Online Access: https://www.mdpi.com/2075-4434/9/2/25

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 <i>Nuclear Spectroscopic Telescope Array (NuSTAR)</i>. 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 K<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>α</mi></semantics></math></inline-formula> emission line at around 6.5 keV. We also estimate the probable mass of the black hole to be <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>6</mn><mo>.</mo><msubsup><mn>5</mn><mrow><mo>−</mo><mn>0.7</mn></mrow><mrow><mo>+</mo><mn>0.5</mn></mrow></msubsup><mspace width="3.33333pt"></mspace><msub><mi>M</mi><mo>⊙</mo></msub></mrow></semantics></math></inline-formula>, with 90% confidence.