Estimating the Convective Turnover Time

The introduction of the Rossby number (R-0), which incorporates the convective turnover time (tau), in 1984 was a pioneering idea for understanding the correlation between stellar rotation and activity. The convective turnover time, which cannot be measured directly, is often inferred using existing tau-mass or tau-color relations, typically established based on an ensemble of different types of stars by assuming that tau is a function of mass. In this work, we use Gaia Early Data Release 3 to demonstrate that the masses used to establish one of the most cited tau-mass relations are overestimated for G-type dwarfs and significantly underestimated for late M dwarfs, offsets that affect studies using this tau-mass relation to draw conclusions. We discuss the challenges of creating such relations then and now. In the era of Gaia and other large data sets, stars used to establish these relations require characterization in a multidimensional space, rather than via the single-characteristic relations of the past. We propose that new multidimensional relations should be established based on updated theoretical models and all available stellar parameters for different interior structures from a set of carefully vetted single stars, so that the convective turnover time can be estimated more accurately.

Automated summary

This study demonstrates the inaccuracies in mass estimation of a commonly used tau-mass relation based on Gaia Early Data Release 3. The findings highlight the importance of establishing multidimensional relations for more accurate estimation of convective turnover time in the era of large data sets.