1. Further Evidence of Modified Spin-down in Sun-like Stars: Pileups in the Temperatureâ€"Period Distribution.
- Author
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David, Trevor J., Angus, Ruth, Curtis, Jason L., van Saders, Jennifer L., Colman, Isabel L., Contardo, Gabriella, Lu, Yuxi, and Zinn, Joel C.
- Subjects
ROSSBY number ,STELLAR rotation ,MAIN sequence (Astronomy) ,DISTRIBUTION of stars ,ANGULAR momentum (Mechanics) - Abstract
We combine stellar surface rotation periods determined from NASA’s Kepler mission with spectroscopic temperatures to demonstrate the existence of pileups at the long-period and short-period edges of the temperatureâ€"period distribution for main-sequence stars with temperatures exceeding âĽ5500 K. The long-period pileup is well described by a curve of constant Rossby number, with a critical value of Ro
crit ≲ Ro⊙ . The long-period pileup was predicted by van Saders et al. as a consequence of weakened magnetic braking, in which wind-driven angular momentum losses cease once stars reach a critical Rossby number. Stars in the long-period pileup are found to have a wide range of ages (âĽ2â€"6 Gyr), meaning that, along the pileup, rotation period is strongly predictive of a star’s surface temperature but weakly predictive of its age. The short-period pileup, which is also well described by a curve of constant Rossby number, is not a prediction of the weakened magnetic braking hypothesis but may instead be related to a phase of slowed surface spin-down due to core-envelope coupling. The same mechanism was proposed by Curtis et al. to explain the overlapping rotation sequences of low-mass members of differently aged open clusters. The relative dearth of stars with intermediate rotation periods between the short- and long-period pileups is also well described by a curve of constant Rossby number, which aligns with the period gap initially discovered by McQuillan et al. in M-type stars. These observations provide further support for the hypothesis that the period gap is due to stellar astrophysics, rather than a nonuniform star formation history in the Kepler field. [ABSTRACT FROM AUTHOR]- Published
- 2022
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