The rotational evolution of low-mass stars

• Applicant: Professor Dr. Klaus G. Strassmeier
• Subject Area: Astrophysics and Astronomy
• Term: from 2008 to 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 76203815

An important aspect in the evolutionary scenario of cool stars is their rotation. Theoretical models already developed make definite and testable predictions of how rotation changes with mass and age. However, a number of physical effects have been added into the models without really knowing if they are necessary, or can be tested observationally. This relates, among other things, to differential rotation vs. solid body models, disk-(or planet)-locking, and magnetic saturation. By measuring stellar rotation very precisely, without aliasing and other non-uniquenesses like, e.g., v sin i that have infected prior data, as a function of stellar mass/color and as a function of stellar age, these observations will simply remove wiggle-room for the models, and specify the rotational evolution of stars empirically. The observations therefore will have a usefulness beyond the testing of any theoretical models. In fact, our survey might lead to a re-evaluation of what is (un-)necessary in the models.We therefore propose to determine, from precise time-series CCD photometry, a large number (≥1,000) of rotation periods for low-mass (mid F, G, K, and early M-type) stars in 12 nearby open clusters with ages between 50 Myr and 1.5 Gyr. At the end of this survey, called the STELLA Open Cluster survey, we will know unambiguously, the main-sequence rotational evolution of FGKM stars as a function of age. The details of the observationally determined dependencies can then be used to understand the global dependencies. The theoretical models would then be stripped down to the bare essentials, and then rebuilt to comply with observations, removing superfluous effects and identifying new dependencies.

• DFG Programme: Research Grants