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Title:
A study of coronal X-ray emission from short-period Algol binaries
Authors:
Singh, K. P.; Drake, S. A.; White, N. E.
Affiliation:
AA(NASA. Goddard Space Flight Center, Greenbelt, MD, US), AB(NASA. Goddard Space Flight Center, Greenbelt, MD, US), AC(NASA. Goddard Space Flight Center, Greenbelt, MD, US)
Publication:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 445, no. 2, p. 840-854 (ApJ Homepage)
Publication Date:
06/1995
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
ECLIPSING BINARY STARS, EMISSION SPECTRA, SPECTRUM ANALYSIS, STELLAR CORONAS, STELLAR ENVELOPES, X RAY SPECTRA, ABUNDANCE, LIGHT CURVE, MATHEMATICAL MODELS, PROPORTIONAL COUNTERS, ROSAT MISSION, STELLAR LUMINOSITY, STELLAR TEMPERATURE
DOI:
10.1086/175744
Bibliographic Code:
1995ApJ...445..840S

Abstract

A study of X-ray emission from five short-period Algol-type binaries based on observations with Advanced Satellite for Cosmology and Astrophysics (ASCA) and ROSAT is presented. We have observed RZ Cas with both satellites, and beta Per, U Cep, delta Lib, and TW Dra with ROSAT. Significant intensity variations are seen in the X-ray emission from RZ Cas, U Cep, TW Dra, and delta Lib. These variations seem unrelated to the eclipsing behavior of these systems and are probably due to either rotational modulation of compact active regions on the surfaces of the chromospherically active secondary components or to flaring activity in the systems. The spectra of all but one of the systems require the presence of at least two discrete plasma components with different temperatures (0.6 - 0.7 keV, and approximately 2 keV) and the abundances of the medium-Z elements 20% - 50% of the solar photospheric values. The high resolving power and signal-to-noise ratio of the ASCA spectra allow us to individually constrain the coronal abundances of O, Ne, Mg, Si, S, and Fe in RZ Cas. We demonstrate that, if we use the elemental abundances and temperatures obtained from the analysis of their ASCA spectra as (fixed) inputs, to fit the ROSAT PSPC spectra well requires the presence of a third component (kT approximately 0.2 - 0.3 keV) in RZ Cas and beta Per. A continuous emission measure model of the power-law type (EM(T) variesas (T/Tmaxalpha) generally gives a poor fit to the ASCA and ROSAT data on most sources. Circumstellar or circumbinary absorbing matter seems to be present in some of these systems, as indicated by the variable total column density needed to fit their X-ray spectra.

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