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Issue A&A
Volume 375, Number 2, August IV 2001
Page(s) 492 - 497
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:20010693



A&A 375, 492-497 (2001)
DOI: 10.1051/0004-6361:20010693

The coronal FeXXI $\lambda$1354.094 line in AB Doradus

O. Vilhu1, P. Muhli1, R. Mewe2 and P. Hakala3

1  Observatory, Box 14, 00014 University of Helsinki, Finland
    e-mail: vilhu@astro.helsinki.fi, muhli@astro.helsinki.fi
2  SRON Laboratory for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
    e-mail: R.Mewe@sron.nl
3  Tuorla Observatory, University of Turku, Finland
    e-mail: pahakala@astro.utu.fi

(Received 10 April 2001 / Accepted 10 May 2001)

Abstract
The active late-type star AB Doradus was observed in February 1996 with the Goddard High Resolution Spectrograph of the Hubble Space Telescope using the low resolution G140L grating. The observations covered one half of the star's rotation cycle (P = 0.514 d) with 11.5 min time resolution. The strong coronal FeXXI $\lambda$1354.094 line formed at 107 K was analysed and its emission measure (EM) derived. This EM is much higher than that derived from recent XMM-Newton observations (Güdel et al. 2001), and earlier EXOSAT (Collier Cameron et al. 1988) and ASCA/EUVE (Mewe et al. 1996) data, as well, requiring a variability by a factor of 5. The physical reason for the variability remains unknown, since (outside flares) the observed broad band variability of AB Dor is much smaller.


Key words: stars: coronae -- stars: activity -- stars: individual: AB Dor -- ultraviolet: stars

Offprint request: O. Vilhu, osmi.vilhu@helsinki.fi

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© ESO 2001


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