CF Tucanae: Another case of a coronal MAD syndrome?

被引:42
作者
Schmitt, JHMM
Stern, RA
Drake, JJ
Kurster, M
机构
[1] UNIV CALIF BERKELEY, CTR EUV ASTROPHYS, BERKELEY, CA 94720 USA
[2] LOCKHEED PALO ALTO RES LABS, SOLAR & ASTROPHYS LAB, PALO ALTO, CA 94304 USA
关键词
binaries; close; stars; coronae; individual (CF Tucanae); ultraviolet;
D O I
10.1086/177378
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We present and discuss an extreme-ultraviolet spectrum of the RS CVn binary CF Tuc obtained with the short-wavelength (SW) spectrometer on board the Extreme-Ultraviolet Explorer (EUVE) satellite. In addition to a continuum, only two spectral lines attributed to Fe XXII and Fe XXIII are detected. We show that the EUVE data can be reconciled with a solar abundance plasma only if most of CF Tuc's emission measure is located at temperatures of approximate to 10(8) K; alternatively, the plasma must be iron depleted with most of the emission measure located at the peak. temperature of the observed line contribution functions. A comparison with previously obtained ROSAT PSPC spectra argues strongly in favor of the latter situation. As a consequence, we are forced to the conclusion that the iron abundance in the corona of CF Tuc is reduced with respect to solar values by factors between 5 and 10. The reasons for the occurrence of this metal abundance deficiency syndrome (MADS) are unclear at present; however, for the specific case of C-F Tuc, the extremely low coronal iron abundance might possibly result from an anomalously low photospheric iron abundance.
引用
收藏
页码:898 / 909
页数:12
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