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The extreme-ultraviolet spectrum of the nearby K dwarf epsilon Eridani
被引:31
作者:
Schmitt, JHMM
Drake, JJ
Stern, RA
Haisch, BM
机构:
[1] UNIV CALIF BERKELEY, CTR EUV ASTROPHYS, BERKELEY, CA 94720 USA
[2] LOCKHEED PALO ALTO RES LABS, DEPT 91 30, PALO ALTO, CA 94304 USA
关键词:
stars;
coronae;
individual (epsilon Eridani);
late-type;
ultraviolet;
D O I:
10.1086/176783
中图分类号:
P1 [天文学];
学科分类号:
0704 ;
摘要:
We present and discuss the extreme-ultraviolet spectrum of the nearby K2 dwarf epsilon Eri obtained with the spectrometers onboard the Extreme-Ultraviolet Explorer satellite (EUVE). In the EUVE spectrum of epsilon Eri we detect emission tines attributable to iron in the ionization stages Fe IX to Fe XXI, thus covering a rather large temperature range from less than 10(6) K to 10(7) K. While the lines in the lowest and highest ionization stages are relatively weak, the strongest lines detected are from Fe XV and Fe XVI, from which we infer a peak in the differential emission measure distribution at coronal temperatures of log T-c similar to 6.4; significant emission measure is, however, also present at both higher and lower temperatures. This is in contrast to both lower activity stars whose EUV spectra are dominated by cooler Fe lines in the range 170-180 Angstrom as well as the more active stars whose EUV spectra are dominated by hotter Fe lines in the range 110-135 Angstrom. Finally, a density determination using line ratios of Fe XIII and Fe XIV results in coronal densities for epsilon Eri which are similar to solar active region densities.
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页码:882 / 891
页数:10
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