Revisiting Stellar equatorial rotational velocities with Gaia DR3 line broadening -- the dependence on temperature, mass and age

TL;DR

This study analyzes Gaia DR3 line broadening data for over 100,000 stars to investigate how stellar rotation varies with temperature, mass, and age, confirming the Kraft break and the role of magnetic braking in stellar spin-down.

Contribution

It provides a comprehensive analysis of stellar rotation dependence on temperature, mass, and age using a large Gaia DR3 dataset, highlighting the different rotational evolution in hot and cool stars.

Findings

Kraft break at ~6500 K or ~1.3 M_sun confirmed

Rotation speeds sharply increase above the Kraft break

Magnetic braking causes slow deceleration in cool stars

Abstract

We used more than $10^5$ Gaia DR3 line broadening vbroad measurements to examine stellar rotation as a function of stellar temperature, mass and age. The large sample clearly displays the Kraft break at $\sim 6{,}500$\,K, or mass of $\sim1.3\,M_{\odot}$-while vbroad are small, on the order of $10$-$20$ km/s, for stars cooler than the Kraft break, they sharply rise above the break, reaching up $\sim100$ km/s with temperature of $7{,}000$ K. To follow the stellar rotation as a function of age, we consider vbroad as a function of scaled age-stellar age divided by the relevant Terminal Age Main Sequence (MS), for four narrow mass bins. We find that stellar rotation deceleration is slow during the MS phase and fast afterwards for stars hotter than the break, whereas deceleration rate is relatively high and does not vary much for the cool stars. Our findings are consistent with the theory that stellar rotation slowing is due to magnetic breaking, emanating from magnetic fields that are anchored to the stellar convective envelopes. Therefore, deceleration is high in cool stars, but in hot stars only after they leave the MS and develop convective outer layers