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Hardness Ratio in Evolving Low-Mass X-ray Binary Systems

Published online by Cambridge University Press:  04 August 2017

J. Shaham
Affiliation:
Columbia Astrophysics Laboratory and Department of Physics, Columbia University, New York, New York 10027
M. Tavani
Affiliation:
Columbia Astrophysics Laboratory and Department of Physics, Columbia University, New York, New York 10027

Extract

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Spectral observations of low-mass X-ray binaries (LMXBs) show that the soft component usually dominates over the hard one. These results provide additional support to an interpretation based on models of LMXBs in which the neutron star while, on the average, spinning up, is also experiencing a spinning down torque. Under these conditions, a fraction of the luminosity associated with the gravitational release of energy on the surface of the accreting neutron star may manifest itself as luminosity originating in the inner part of the accretion disk. It is probably possible to separate the two contributions; the stellar luminosity can be associated with the hard component of the spectrum and the disk luminosity, related to the exchange of energy due to the torque between the rapidly spinning neutron star and the accretion disk, can be associated with the soft spectral component.

Type
II. Accretion Powered Pulsars
Copyright
Copyright © Reidel 1987