The age distribution of stars in the immediate solar environment

• Applicant: Professor Dr. Jürgen H.M.M. Schmitt
• Subject Area: Astrophysics and Astronomy
• Term: from 2015 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 283666120

• Final Report Year: 2020

Final Report Abstract

The project goal, i.e., the determination of rotation periods of a complete sample of nearby stars, could not be fully reached. It is a little sobering to realize that a fundamental parameter of a star such as its rotation rate cannot be (easily) determined for even those stars that are most amenable to studies. In the end this is of course not surprising. If we were faced with a completely immaculate star without any surface inhomogeneities, we could determine only its v-sin(i) value, and for slow rotators this is next to impossible. Also the Sun, when viewed as a star, does not easily offer the luxury to measure its period through rotational modulation in integral light, one has to select the proper wavelength range and period. In the course of the project work we obtained quite a few new and unexpected results, some of the ”bread and butter” type (such as new binaries with their orbits) and other quite exciting results such as the discovery of short term magnetic cycles on the order of a few months for F-type stars.

Publications

• 2017, A&A, 600 A119: ”Four-month chromospheric and coronal activity cycle in τ Boötis”
  Mittag, M.,Robrade, J., Schmitt, J. H. M. M., Hempelmann, A., Gonzalez-Perez, J. N., Schröder, K. -P.
  (See online at https://doi.org/10.1051/0004-6361/201629156)
• A&A, 2017, 600, A125: ”Further evidence for a sub-year magnetic chromospheric activity cycle and activity phase jumps in the planet host τ Boötis”
  Schmitt, J. H. M. M., Mittag, M.
  (See online at https://doi.org/10.1051/0004-6361/201629429)
• 2018, A&A, 618, A48: ”Revisiting the connection between magnetic activity, rotation period, and convective turnover time for main-sequence stars”
  Mittag, M., Schmitt, J. H. M. M., Schröder, K.-P.
  (See online at https://doi.org/10.1051/0004-6361/201833498)
• 2019, A&A, 621, 136: ”Discovery of short-term activity cycles in F-type stars”
  Mittag, M., Schmitt, J. H. M. M., Hempelmann, A., Schröder, K.-P.
  (See online at https://doi.org/10.1051/0004-6361/201834319)
• 2019, A&A, 628, 107: ”Magnetic activity of the solar-like star HD 140538”
  Mittag, M.,Schmitt, J. H. M. M., Metcalfe, T. S., Hempelmann, A.,Schröder, K.-P.
  (See online at https://doi.org/10.1051/0004-6361/201935654)
• 2020, AN, 341, 497: ”Rotation of solar-like stars in the immediate solar neighborhood”
  Schmitt, J. H. M. M., Mittag, M.
  (See online at https://doi.org/10.1002/asna.202013790)