Volume 473, Number 2, October II 2007
|Page(s)||561 - 568|
|Section||Stellar structure and evolution|
|Published online||06 August 2007|
XMM-Newton and INTEGRAL observations of the black hole candidate XTE J1817-330*
Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany e-mail: email@example.com
Accepted: 23 July 2007
Aims.The galactic black hole candidate XTE J1817-330 was discovered in outburst by RXTE in January 2006. We present here the results of an XMM-Newton target of opportunity observation, performed on 13 March 2006 (44 days after the maximum), and an INTEGRAL observation performed on 15–18 February 2006 (18 days after the maximum).
Methods.The EPIC-pn camera on-board XMM-Newton was used in the fast read-out burst mode to avoid photon pile-up, while the RGS was used in spectroscopy high count rate mode. We fit both the XMM-Newton and the INTEGRAL spectra with a two-component model consisting of a thermal accretion disk (represented by diskbb or diskpn models) and a comptonizing hot corona (represented by a power-law or the compTT model).
Results.The soft X-ray spectrum is dominated by an accretion disk component, with a maximum temperature decreasing from 0.96±0.04 keV at the time of the INTEGRAL observation to 0.70±0.01 keV on 13 March. The optical monitors on board INTEGRAL and XMM-Newton showed the source with magnitudes V:11.3–11.4, U:15.0–15.1 and UVW1:14.7–14.8. The soft X-ray spectrum, together with the optical and UV data, show a low hydrogen column density towards the source, and several absorption lines, most likely of interstellar origin, are detected in the RGS spectrum: OIKα, OIKβ, OII, OIII and OVII, which trace both cold and hot components of the interstellar medium. The soft X-ray spectrum indicates the presence of a black hole, with an estimate for the upper limit of the mass of 6.0 .
Key words: stars: binaries / X-rays: individual: XTE J1817-330 / stars: binaries: close
Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA; and with INTEGRAL, an ESA project with instruments and science data center funded by ESA member states (especially the PI countries: Denmark, France, Germany, Italy, Switzerland, Spain), Czech Republic and Poland, and with the participation of Russia and the USA.
© ESO, 2007
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