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
相关论文
共 37 条
  • [11] KURSTER M, 1994, ASTR SOC P, V64, P104
  • [12] KURSTER M, 1993, ASTROPHYS SPACE SC L, V184, P443
  • [13] KURSTER M, 1996, IN PRESS A A
  • [14] LANDINI M, 1990, ASTRON ASTROPHYS SUP, V82, P229
  • [15] LEMEN JR, 1984, ASTRON ASTROPHYS, V135, P313
  • [16] NEW CALCULATIONS OF FE L-SHELL X-RAY-SPECTRA IN HIGH-TEMPERATURE PLASMAS
    LIEDAHL, DA
    OSTERHELD, AL
    GOLDSTEIN, WH
    [J]. ASTROPHYSICAL JOURNAL, 1995, 438 (02) : L115 - L118
  • [17] A SYSTEMATIC SEARCH FOR LONG-TERM VARIABILITY IN A LARGE SAMPLE OF X-RAY SOURCES
    MACCACARO, T
    GARILLI, B
    MEREGHETTI, S
    [J]. ASTRONOMICAL JOURNAL, 1987, 93 (06) : 1484 - 1501
  • [18] EXTREME-ULTRAVIOLET EXPLORER BRIGHT SOURCE LIST
    MALINA, RF
    MARSHALL, HL
    ANTIA, B
    CHRISTIAN, CA
    DOBSON, CA
    FINLEY, DS
    FRUSCIONE, A
    GIROUARD, FR
    HAWKINS, I
    JELINSKY, P
    LEWIS, JW
    MCDONALD, JS
    MCDONALD, K
    PATTERER, RJ
    SABA, VW
    SIRK, MM
    STROOZAS, BA
    VALLERGA, JV
    VEDDER, PW
    WIERCIGROCH, A
    BOWYER, S
    [J]. ASTRONOMICAL JOURNAL, 1994, 107 (02) : 751 - 764
  • [19] Mewe R., 1985, Astronomy & Astrophysics Supplement Series, V62, P197
  • [20] MEWE R, 1995, ASTRON ASTROPHYS, V296, P477