The beta Pictoris association low-mass members: membership assessment, rotation period distribution, and dependence on multiplicity

TL;DR

This study assesses the rotation periods of low-mass members of the 25-Myr beta Pictoris association, analyzing the influence of multiplicity on rotation and its potential as an age indicator, revealing distinct patterns based on binary separation.

Contribution

It provides the most extensive list of low-mass beta Pictoris members, measures their rotation periods, and analyzes how multiplicity affects stellar rotation evolution.

Findings

Wide orbit multiple systems have similar rotation periods to single stars.

Close orbit multiple systems have significantly shorter rotation periods.

Rotation period evolution models fit F-G stars but not slow K and M stars.

Abstract

Low-mass members of young stellar associations exhibit a wide spread of rotation periods. Such a spread originates from distributions of masses and initial rotation periods. However, multiplicity can also play a significant role. We investigate the role played by physical companions in shortening the primordial disc lifetime. We have compiled the most extensive list of low-mass members of the young 25-Myr beta Pictoris association. We have measured the rotation periods of about all members and used updated UVWXYZ components to assess their membership. We built the rotation period distribution distinguishing between bona fide members and candidate members and according to their multiplicity status. We found that single stars and components of multiple systems in wide orbits (>80 AU) have rotation periods that exhibit a well defined sequence arising from mass distribution. All components of multiple systems in close orbits (<80 AU) have rotation periods significantly shorter than their equal-mass single counterparts. A comparison with the younger 13 Myr h Per cluster and with the older 40-Myr open clusters/stellar associations NGC2547, IC2391, Argus, and IC2602 and the 130-Myr Pleiades shows that whereas the evolution of F-G stars is well reproduced by angular momentum evolution models, this is not the case for the slow K and early-M stars. Finally, we found that the amplitude of their light curves is correlated neither with rotation nor with mass. Once single stars and wide components of multiple systems are separated from close components of multiple systems, the rotation period distributions exhibit a well defined dependence on mass that allows to make a meaningful comparison with similar distributions of either younger or older associations/clusters. Such cleaned distributions allow to use the stellar rotation period as age indicator, meaningfully for F and G type stars.