Calibrating Stellar Gyrochronology Using Improved Rotation Period Measurements

Stellar rotation provides a promising, yet flawed means for age-dating stars. Recent surveys of rotation in open clusters revealed that spin-down stalls for an extended period of time, the duration of which increases toward lower stellar masses. This research program will improve rotation-based age-dating techniques for low-mass stars (40-130% of the Sun's mass) by calibrating 'gyrochronology' with a modern, expanded database of rotation period measurements for benchmark star clusters. The PI is the founder of the Columbia University Bridge to the Ph.D. in STEM Program. For twelve years, the Bridge program has increased the number of underrepresented scholars entering STEM Ph.D. programs and to equip them to succeed in these programs. A Bridge scholar will play a leading role in this research program, with careful mentoring from the senior researchers on the team.

The project will determine when stars converge on the slow sequence by examining nearby and young open clusters and moving groups observed by TESS (50-500 Myr). Next, Kepler, K2, and PTF data for older clusters (>1 Gyr) will be analyzed to constrain the stalling timescale and the subsequent rate of spin-down. This will inform a new empirical model that will describe all the observed phases of spin-down in stars of different masses. Finally, the impact of metallicity on rotational evolution will be tested using sets of coeval but chemically different clusters. For example, rotation period distributions will be produced for NGC 6866 using Kepler data, and Coma Ber using TESS data. These sequences will be compared to those for Praesepe and the Hyades, which are approximately coeval (all ~700 Myr) but are 0.2 dex richer in metallicity than the target clusters. Determining this sensitivity to metallicity is critical for inferring accurate rotation-based ages for field stars.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.