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Title:
An ASCA observation of one orbital cycle of AR Lacertae
Authors:
White, Nicholas E.; Arnaud, Keith; Day, Charles S. R.; Ebisawa, Ken; Gotthelf, Eric V.; Mukai, Koji; Soong, Yang; Yaqoob, Tahir; Antunes, Alex
Affiliation:
AA(Laboratory for High Energy Astrophysics, Greenbelt, MD, US), AB(Laboratory for High Energy Astrophysics, Greenbelt, MD, US), AC(Laboratory for High Energy Astrophysics, Greenbelt, MD, US), AD(Laboratory for High Energy Astrophysics, Greenbelt, MD, US), AE(Laboratory for High Energy Astrophysics, Greenbelt, MD, US), AF(Laboratory for High Energy Astrophysics, Greenbelt, MD, US), AG(Laboratory for High Energy Astrophysics, Greenbelt, MD, US), AH(Laboratory for High Energy Astrophysics, Greenbelt, MD, US), AI(Institute of Space and Astronautical Science, Sagamihara, Japan)
Publication:
PASJ: Publications of the Astronomical Society of Japan, vol. 46, no. 3, p. L97-L100 (PASJ Homepage)
Publication Date:
06/1994
Category:
Astronomy
Origin:
STI
NASA/STI Keywords:
ABUNDANCE, ECLIPSING BINARY STARS, METALLICITY, STELLAR LUMINOSITY, X RAY BINARIES, X RAY SPECTRA, CHARGE COUPLED DEVICES, LIGHT CURVE, STELLAR MODELS, STELLAR RADIATION
Bibliographic Code:
1994PASJ...46L..97W

Abstract

An Advanced Satellite for Cosmology and Astrophysics (ASCA) observation of one complete 2-day orbit of the eclipsing RS CVn binary AR Lac is reported. The time averaged X-ray spectrum reveals an emission line from Fe K at 6.7 keV, lines at lower energies from the Fe L complex, and K lines of Si, S, and other medium-Z elements. The previously established two-temperature thermal equilibrium emission model was fit to the spectra, but gives a poor fit. An improved fit is obtained if the abundance of O, Mg, Si, S, Ar, Ca, and Fe are 2-4 times less than the solar photospheric value. The underabundance of these elements lends support to the idea that weaker than expected absorption lines in the optical spectra of the secondary stars in RS CVn binaries are caused by these stars being metal poor. The overall orbital lightcurve is similar to that seen previously with a 50% reduction in flux centered on the primary eclipse and energy independent across the 0.4-7 keV band. At energies greater than keV the lightcurve shows continuous low level flaring activity on a timescale of 20-60 min.

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