Astronomy and Astrophysics
Aims: The goal of this study is to identify the most promising cool main-sequence stellar candidates for anti-solar differential rotation in the Kepler sample.
Methods: First, we introduce a new theoretical formula to estimate fluid Rossby numbers, Rof, of main-sequence solar-type stars. We derived it from observational quantities such as Teff and Prot, and took the influence of the internal structure into account. Then, we applied it on a subset of the most recent catalog of Kepler rotation periods, after removing subgiants and selecting targets with solar metallicity. Next, we considered the highest computed Rof and inspected each target individually to select the most reliable anti-solar candidate. Finally, we extended our study to stars with metallicities different from that of the Sun. To this end, we developed a formulation for Rof dependent on the metallicity index [Fe/H] by using 1D stellar grids, and we also considered this compositional aspect for the selection of the targets.
Results: We obtain a list of the most promising stars that are likely to show anti-solar differential rotation. We identify two samples: one at solar metallicity, including 14 targets, and another for other metallicities, including 8 targets. We find that the targets with the highest Rof are likely to be early-G or late-F stars at about log10g = 4.37 dex.
Conclusions: We conclude that cool main-sequence stellar candidates for anti-solar differential rotation exist in the Kepler sample. The most promising candidate is KIC 10907436, and two other particularly interesting candidates are the solar analog KIC 7189915 and the seismic target KIC 12117868. Future characterization of these 22 stars is expected to help us understand how dynamics can impact magnetic and rotational evolution of old solar-type stars at high Rossby number. Full Table B.1 is only available at the CDS via anonymous ftp to cdsarc.cds.unistra.fr (ftp://188.8.131.52) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/667/A50
The principal objectives of this project are: 1) to study the structure and dynamics of the solar interior, 2) to extend this study to other stars, 3) to search for extrasolar planets using photometric methods (primarily by transits of their host stars) and their characterization (using radial velocity information) and 4) the study of the planetary