Issue |
A&A
Volume 417, Number 2, April II 2004
|
|
---|---|---|
Page(s) | 381 - 389 | |
Section | Astrophysical processes | |
DOI | https://doi.org/10.1051/0004-6361:20031765 | |
Published online | 19 March 2004 |
Evolution of X-ray spectra in down-Comptonization. A comparison of the extended Kompaneets equation with Monte Carlo simulation and the Ross-McCray equation
1
Institute for Space and Astrophysics, Department of Physics, Shanghai Jiao Tong University, Shanghai 200030, PR China
2
Laboratory for High Energy Astrophysics, NASA/GSFC Code 661, Greenbelt, Maryland 20771, USA
Corresponding author: D.-B. Liu, dbliu@sjtu.edu.cn
Received:
13
May
2003
Accepted:
18
November
2003
The original Kompaneets equation fails to describe down-Comptonization, which is the most
important radiative transfer process in hard X-ray and γ-ray astronomy, compared
with up-Comptonization. In this paper, we improve our previous derivation of the extended
Kompaneets equation and present it more clearly. The new equation can be used to describe
a more general Comptonization process, including up- and down-Comptonization, suitable for
any case, ,
and
. The condition of the original Kompaneets equation
is no longer necessary. Using the extended equation,
we give some typical solutions in X-ray astronomy, and compare them with those of the
prevailing Monte Carlo simulations and the Ross-McCray equation. The excellent consistency
between the extended Kompaneets equation and Monte Carlo simulation or Ross-McCray equation
confirms the correctness of our extended Kompaneets equation. The numerical solution of
the extended Kompaneets equation is less expensive in terms of computational time than
the Monte Carlo simulation. Another advantage of the equation method is the simplicity
and the clarity in physics. The potential applications in X-ray and
γ-ray astronomy are also emphasized.
Key words: scattering / radiative transfer / methods: analytical / X-rays, γ-rays: ISM
© ESO, 2004
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