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Title: Detection of pulsating soft X-ray excess in the Magellanic Cloud pulsars with ASCA
Authors: Paul, Biswajit
Yokogawa, J.
Nishiuchi, M.
Endo, T.
Dotani, T.
Nagase, F.
Issue Date: Jan-2001
Publisher: Elsevier B.V.
Citation: Advances in Space Research, 2001, Vol. 28, p399-403
Abstract: The binary X-ray pulsars which are away from the galactic plane and therefore experience less interstellar absorption, show the presence of a soft component in the spectrum which is often described as a black-body and/or thermal bremsstrahlung emission. A thermal component for the soft excess provides a satisfactory model in the Galactic sources like Her X-1 and 4U 1626-67. But for the pulsars in the Magellanic Clouds for which the distance is of the order of 60 kpc and the luminosity is close to the Eddington limit, a soft component dominating in the lower energy part of the spectrum requires emission region which is a few orders of magnitude larger than the size of a neutron star. Using ASCA observations, we show that a pulsating nature of the soft component in several bright pulsars is difficult to explain if a thermal origin is assumed for the low energy part of the spectrum. We investigate whether a two component power-law with different absorptions or an inversely broken power-law can instead explain the pulsations at low energy. A soft power-law component may also be a common feature of the binary X-ray pulsars, which is difficult to observe because most of the sources are in the galactic plane and experience large interstellar absorption.
Description: Restricted Access
ISSN: 0273-1177
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Copyright: 2001 Elsevier B.V.
Appears in Collections:Research Papers (A&A)

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