Volume 394, Number 2, November I 2002
|Page(s)||553 - 560|
|Section||Interstellar and circumstellar matter|
|Published online||15 October 2002|
Broad-band X-ray measurements of the black hole candidate XTE J1908+094
Astronomical Institute, Utrecht University, PO Box 80000, 3508 TA Utrecht, The Netherlands
2 SRON National Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
3 Center for Space Research and Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA
4 Astrophysics Division, Research & Scientific Support Department, ESA, ESTEC SCI-SA, 2200 AG Noordwijk, The Netherlands
Corresponding author: J. J. M. in 't Zand, email@example.com
Accepted: 1 August 2002
XTE J1908+094 is an X-ray transient that went into outburst in February 2002. After two months it reached a 2–250 keV peak flux of 1 to erg cm-2 s-1. Circumstantial evidence points to an accreting galactic black hole as the origin of the X-radiation: pulsations nor thermonuclear flashes were detected that would identify a neutron star and the spectrum was unusually hard for a neutron star at the outburst onset. We report on BeppoSAX and RXTE All Sky Monitor observations of the broad-band spectrum of XTE J1908+094. The spectrum is consistent with a model consisting of a Comptonization component by a ~40 keV plasma, a multicolor accretion disk blackbody component with a temperature just below 1 keV and a broad emission line at about 6 keV. The spectrum is heavily absorbed by cold interstellar matter with an equivalent hydrogen column density of cm-2, which makes it difficult to study the black body component in detail. The black body component exhibits strong evolution about 6 weeks into the outburst. Two weeks later this is followed by a swift decay of the power law component. The broadness of the 6 keV feature may be due to relativistic broadening or Compton scattering of a narrow Fe-K line.
Key words: accretion, accretion disks / binaries: close / X-rays: individual: XTE J1908+094
© ESO, 2002
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