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

Abstract

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+/-0.4 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.

arXiv comment6 pages, 7 figures, accepted for publication in A&A

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• Variable Star Network: World Center for Transient Object Astronomy and Variable Stars
• Secular Evolution in Mira Variable Pulsations
• The evolutionary state of Miras with changing pulsation periods
• Period and chemical evolution of SC stars
• Stellar Evolution in Real Time: Models Consistent with Direct Observation of Thermal Pulse in T Ursae Minoris
• Semi-regular red giants as distance indicators I. The period-luminosity relations of semi-regular variables revisited
• Hydrodynamic modelling of pulsation period decrease in the Mira-type variable T UMi
• Pulsations of intermediate-mass stars on the asymptotic giant branch
• Wavelets with Ridges: A High-Resolution Representation of Cataclysmic Variable Time-Series
• Nonlinear pulsations of stars with initial mass 3 M_\odot on the asymptotic giant branch
• A model of the Mira-type star T UMi