EDP Sciences
Free access
Volume 398, Number 1, January IV 2003
Page(s) 277 - 282
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:20021646

A&A 398, 277-282 (2003)
DOI: 10.1051/0004-6361:20021646

The He-shell flash in action: T Ursae Minoris revisited

K. Szatmáry, L. L. Kiss and Zs. Bebesi

Department of Experimental Physics and Astronomical Observatory, University of Szeged, Szeged, Dóm tér 9., 6720 Hungary
(Received 15 October 2002 / Accepted 7 November 2002)

We present an updated and improved description of the light curve behaviour of T Ursae Minoris, which is a Mira star with the strongest period change (the present rate is an amazing $-3.8\pm0.4$ days/year corresponding to a relative decrease of about 1% per cycle). Ninety years of visual data were collected from all available databases and the resulting, almost uninterrupted light curve was analysed with the O-C diagram, Fourier analysis and various time-frequency methods. The Choi-Williams and Zhao-Atlas-Marks distributions gave the clearest image of frequency and light curve shape variations. A decrease of the intensity average of the light curve was also found, which is in accordance with a period-luminosity relation for Mira stars. We predict the star will finish its period decrease in the meaningfully near future (c.c. 5 to 30 years) and strongly suggest to closely follow the star's variations (photometric, as well as spectroscopic) during this period.

Key words: stars: variables: general -- stars: oscillations -- stars: AGB and post-AGB -- stars: individual: T UMi

Offprint request: K. Szatmáry, k.szatmary@physx.u-szeged.hu

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