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To Understand the UV-optical Excess of RX J1856.5-3754

Y. L. Yue·X. H. Cui·R. X. Xu
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Abstract

The enigma source, RX J1856.5-3754, is one of the so-called dim thermal neutron stars. Two puzzles of RXJ1856.5-3754 exist: (1) the observational X-ray spectrum is completely featureless; (2) the UV-optical intensity is about seven times larger than that given by the continuation of the blackbody model yielded by the X-ray data. Both the puzzles would not exist anymore if RX J1856.5-3754 is a low mass bare strange quark star, which is in a propeller phase with a low accretion rate. A boundary layer of RX J1856.5-3754 is suggested and modelled, from which the UV-optical emission is radiated. Free-free absorption dominates the opacity of the boundary layer, which results in the opacity to be high in UV-optical but low in X-ray bands. The star's magnetic field, spin period, as well as the accretion rate are constrained by observations.

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Y. L. Yue, X. H. Cui, R. X. Xu. 2005-10-02. To Understand the UV-optical Excess of RX J1856.5-3754. https://arxiv.org/abs/astro-ph/0510020

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