Da-Bin Lin, Wei-Min Gu, Tong Liu, Ju-Fu Lu
In accretion systems, outflows may have significant influence on the
luminosity fluctuations. In this paper, following the Lyubarskii's general
scheme, we revisit the power spectral density of luminosity fluctuations by
taking into account the role of outflows. Our analysis is based on the
assumption that the coupling between the local outflow and inflow is weak on
the accretion rate fluctuations. We find that, for the inflow mass accretion
rate $\dot M \propto r^{s}$, the power spectrum of flicker noise component will
present a power-law distribution $p(f) \propto f^{-(1+4s/3)}$ for
advection-dominated flows. We also obtain descriptions of $p(f)$ for both
standard thin discs and neutrino-cooled discs, which show that the power-law
index of a neutrino-cooled disc is generally larger than that of a
photon-cooled disc. Furthermore, the obtained relationship between $p(f)$ and
$s$ indicates the possibility of evaluating the strength of outflows by the
power spectrum in X-ray binaries and gamma-ray bursts. In addition, we discuss
the possible influence of the outflow-inflow coupling on our results.
View original:
http://arxiv.org/abs/1112.0355
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