Broad-band X-ray measurements of the black hole candidate XTE J1908+094
Abstract
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 2*E-8 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 2.5*E22 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.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- November 2002
- DOI:
- 10.1051/0004-6361:20021123
- arXiv:
- arXiv:astro-ph/0205535
- Bibcode:
- 2002A&A...394..553I
- Keywords:
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- accretion;
- accretion disks;
- binaries: close;
- X-rays: individual: XTE J1908+094;
- Astrophysics
- E-Print:
- Accepted for publication in Astronomy &