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Astron. Astrophys. 361, 321-326 (2000)

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Profiles of thermal line emission from advection dominated accretion flows

X. Cao 1,2, Y.D. Xu 3 and J.H. You 3

1 Chinese Academy of Sciences, Shanghai Astronomical Observatory, 80 Nandan Road, Shanghai, 200030, P.R. China
2 Beijing Astrophysical Center (BAC), P.R. China
3 Shanghai Jiaotong University, Department of Applied Physics, Shanghai, 200030, P.R. China

Received 26 January 2000 / Accepted 11 July 2000


Recently, Narayan & Raymond (1999) proposed that the thermal emission lines from the hot plasma in advection dominated accretion flows (ADAFs) are potentially observable with the next generation of X-ray observatories, with which the physical properties of some X-ray sources can be probed. In ADAFs, the temperature of the ion is so high that the thermal broadening of the line is important. We calculate the profiles of thermal line emission from ADAFs, in which both the thermal and Doppler broadening have been considered. It is found that the double-peaked profiles are present for high inclination angles between the axis of disk and the line of sight. The double-peaked profiles are smeared in low inclination cases, and completely disappear when the inclination angle is less than [FORMULA], where the thermal and turbulent broadening dominated on the line profiles. We also note that the thermal line profile is affected by the location of the transition radius of ADAF. The self-similar height-integrated disk structure and the emissivity with power-law dependence of radius are adopted in our calculations. The results obtained in this work can be used as a diagnosis on the future X-ray observations of the thermal lines. Some important physical quantities of ADAFs could be inferred from future thermal line observations.

Key words: accretion, accretion disks – line: profiles – X-rays: general

Send offprint requests to: Xinwu Cao (cxw@center.shao.ac.cn)

© European Southern Observatory (ESO) 2000

Online publication: September 5, 2000