NuSTAR and Swift observations of the black hole candidate XTE J1908+094 during its 2013 outburst

Abstract

The black hole candidate XTE J1908+094 went into outburst for the first time since 2003 in October 2013. We report on an observation with the Nuclear Spectroscopic Telescope Array (NuSTAR) and monitoring observations with Swift during the outburst. NuSTAR caught the source in the soft state: the spectra show a broad relativistic iron line, and the light curves reveal a ~40 ks flare with the count rate peaking about 40% above the non-flare level and with significant spectral variation. A model combining a multi-temperature thermal component, a power-law, and a reflection component with an iron line provides a good description of the NuSTAR spectrum. Although relativistic broadening of the iron line is observed, it is not possible to constrain the black hole spin with these data. The variability of the power-law component, which can also be modeled as a Comptonization component, is responsible for the flux and spectral change during the flare, suggesting that changes in the corona (or possibly continued jet activity) are the likely cause of the flare.

9 pages, 6 figures, 3 tables, accepted for publication in ApJ

References in corpus (5)

• X-ray Properties of Black-Hole Binaries
• Relativistic X-ray Lines from the Inner Accretion Disks Around Black Holes
• The role of the reflection fraction in constraining black hole spin
• Correlated radio--X-ray variability of Galactic Black Holes: A radio--X-ray flare in Cygnus X-1
• Radio polarimetry as a probe of unresolved jets: the 2013 outburst of XTE J1908+094

Cited by in corpus (10)

• Normalizing a Relativistic Model of X-ray Reflection: The Definition of the Reflection Fraction and its Implementation in relxill
• The Soft State of Cygnus X-1 Observed with NuSTAR: A Variable Corona and a Stable Inner Disk
• Resolved, expanding jets in the Galactic black hole candidate XTE J1908+094
• Evolution of the accretion disk-corona during bright hard-to-soft state transition: A reflection spectroscopic study with GX 339-4
• A variable ionized disk wind in the black-hole candidate EXO 1846-031
• Testing wind as an explanation for the spin problem in the continuum-fitting method
• Insight-HXMT Study of the Inner Accretion Disk in the Black Hole Candidate EXO 1846--031
• Peculiar disk behaviors of the black hole candidate MAXI J1348-630 in the hard state observed by Insight-HXMT and Swift
• Properties of Faint X-ray Activity of XTE J1908+094 in 2019
• The Spin and Orientation of the Black Hole in XTE J1908$+$094