Stellar age dependence of the nonextensive magnetic braking index: a test for the open cluster $\alpha$Per

TL;DR

This study examines how the magnetic braking index $q$ evolves with stellar age across multiple open clusters, finding it remains nearly constant, suggesting a time-independent mechanism for stellar rotational decay.

Contribution

It introduces a generalized spin-down law to analyze the age dependence of the magnetic braking index $q$ using data from nine open clusters, providing new insights into stellar rotational evolution.

Findings

The $q$-index remains nearly constant around 1.36-1.38 over time.

The rotational decay mechanism appears independent of stellar age.

Results support a time-invariant magnetic braking process.

Abstract

Using a generalized function of the stellar spin-down law, we investigate the age dependence of the magnetic braking index ($q$). Our survey includes 9 open clusters aged lower than 1 Gyr and ranged in mass from 0.7 to 1.1$M_{\odot}$. Our aim is to verify the time behavior of the nonextensive braking index $q$ which brings the cumulative distribution of the rotational velocities of the stars of the youngest cluster ($\alpha{\rm Per}$) taken at the future age of an older cluster. As a result, the $q$-index is calculated over time $t-t_{\alpha{\rm Per}}$, where $t$ is the age of older open cluster used to estimate the future cumulative distribution of the rotational velocity of the $\alpha{\rm Per}$ cluster with present-day age $t_{\alpha{\rm Per}}$. We find that the values of $q$ are slightly constant around 1.36 and 1.38 according to the mass bin. In conclusion, the results seem to indicate that the mechanism that controls the rotational decay of stars in open clusters does not depend on the increment of time.