NuSTAR and SWIFT Observations of the Black Hole Candidate XTE J1908+094 during its 2013 Outburst

Lian Tao, John A. Tomsick, Dominic J. Walton, Felix Fuerst, Jamie Kennea, Jon M. Miller, Steven E. Boggs, Finn Erland Christensen, William W. Craig, Poshak Gandhi, Brian W. Grefenstette, Charles J. Hailey, Fiona A. Harrison, Hans A. Krimm, Katja Pottschmidt, Daniel Stern, Shriharsh P. Tendulkar, William W. Zhang

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The black hole (BH) candidate XTE J1908+094 went into outburst for the first time since 2003 in 2013 October. 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 similar to 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 BH 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.
Original languageEnglish
Article number51
JournalAstrophysical Journal
Number of pages9
Publication statusPublished - 2015


  • Accretion
  • Accretion disks
  • Black hole physics
  • Stars: individual (XTE J1908+094)
  • X-rays: binaries

Cite this

Tao, L., Tomsick, J. A., Walton, D. J., Fuerst, F., Kennea, J., Miller, J. M., Boggs, S. E., Christensen, F. E., Craig, W. W., Gandhi, P., Grefenstette, B. W., Hailey, C. J., Harrison, F. A., Krimm, H. A., Pottschmidt, K., Stern, D., Tendulkar, S. P., & Zhang, W. W. (2015). NuSTAR and SWIFT Observations of the Black Hole Candidate XTE J1908+094 during its 2013 Outburst. Astrophysical Journal, 811, [51].