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Astron. Astrophys. 343, 175-182 (1999)

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Evolved, single, slowly rotating ... but magnetically active

The G8-giant HR 1362 = EK Eridani revisited

K.G. Strassmeier  *  1, K. Stepie 2, G.W. Henry 3 and D.S. Hall 4

1 Institut für Astronomie, Universität Wien, Türkenschanzstrasse 17, A-1180 Wien, Austria (e-mail: strassmeier@astro.univie.ac.at)
2 Warsaw University Observatory, Al. Ujazdowskie 4, PL-00-478 Warszawa, Poland (e-mail: kst@coma.astrouw.edu.pl)
3 Ctr. of Excellence in Information Systems, Tennessee State University, Nashville, TN 37203, USA (e-mail: henry@schwab.tsuniv.edu)
4 Dyer Observatory, Vanderbilt University, Nashville, TN 37235, USA (e-mail: hallxxds@ctrvax.vanderbilt.edu)

Received 27 August 1998 / Accepted 7 December 1998

Abstract

We rediscuss the unusual case of the slowly rotating late-type giant HR 1362, which exhibits a very unusual high level of magnetic activity. New BVRI photometry from two robotic telescopes from 1991 through 1998 together with previously published photometric data gives a very precise photometric period of 306.9[FORMULA]0.4 days. With the aid of high-resolution (R=120,000) optical spectra and the Hipparcos parallax we redetermine the absolute parameters of HR 1362 and find it to be a single G8IV-III star of 14 L[FORMULA] and a mass of 1.85 M[FORMULA] with [FORMULA]=5125 K, [FORMULA]=3.25, and solar abundances. Lithium is not significantly different from solar and we obtain [FORMULA](Li)=1.14 from a detailed spectrum synthesis including both isotopes at 6708 Å. [FORMULA] and macroturbulence are determined from fits of disk-integrated models to the observed line profiles as well as their Fourier transforms and are 1.5[FORMULA]0.5 km s-1 and [FORMULA]5 km s-1, respectively. The minimum radius from [FORMULA] and [FORMULA] is only then in agreement with the spectral classification and the bolometric luminosity from the Hipparcos parallax if the inclination of the stellar rotation axis is nearly [FORMULA]. We concur with the arguments of Stepie (1993) that HR 1362 is an evolved Ap star, and therefore the magnetic field is possibly of galactic origin rather than dynamo generated.

Key words: stars: activity – stars: individual: HR 1362 – stars: late-type – stars: rotation – stars: starspots

* Visiting Astronomer, Kitt Peak National Observatory, operated by the Association of Universities for Research in Astronomy, Inc. under contract with the National Science Foundation and at Canada-France-Hawaii Telescope, operated by the National Research Council of Canada, the Centre National de la Recherche Scientifique de France, and the University of Hawaii

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© European Southern Observatory (ESO) 1999

Online publication: March 1, 1999
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