Effect of metallicity on the detectability of rotational periods in solar-like stars

V Witzke,S K Solanki,A I Shapiro,T Reinhold,N A Krivova

doi:10.1051/0004-6361/201936608

V Witzke, S K Solanki + Show 3 more

Open Access

https://doi.org/10.1051/0004-6361/201936608

Copy DOI

Abstract

The accurate determination of stellar rotation periods is important for estimating stellar ages and for understanding stellar activity and evolution. While rotation periods can be determined for about thirty thousand stars in the Kepler field, there are over one hundred thousand stars, especially with low photometric variability and irregular pattern of variations, for which rotational periods are unknown. Here we investigate the effect of metallicity on the detectability of rotation periods. This is done by synthesising light curves of hypothetical stars that are identical to our Sun with the exception of the metallicity. These light curves are then used as an input to the period determination algorithms. We find that the success rate for recovering the rotation signal has a minimum close to the solar metallicity value. This can be explained by the compensation effect of facular and spot contributions. In addition, selecting solar-like stars with near-solar effective temperature and photometric variability, and with metallicity between M/H = −0.35 and M/H = 0.35 from the Kepler sample, we analyse the fraction of stars for which rotational periods have been detected as a function of metallicity. In agreement with our theoretical estimate we find a local minimum for the detection fraction close to the solar metallicity. We further report rotation periods of 87 solar-like Kepler stars for the first time.

Highlights

The rotation period of a star is a fundamental stellar parameter that is closely linked to the stellar age, and determines its magnetic activity. Skumanich (1972) was the first to demonstrate that the equatorial rotational velocity and magnetic activity decrease with stellar age t as 1/ t
We find that the success rate for recovering the rotation signal has a minimum close to the solar metallicity value
In agreement with our theoretical estimate we find a local minimum for the detection fraction close to the solar metallicity

Summary

Introduction

The rotation period of a star is a fundamental stellar parameter that is closely linked to the stellar age, and determines its magnetic activity. Skumanich (1972) was the first to demonstrate that the equatorial rotational velocity and magnetic activity (the latter expressed via the emission i√n the Ca ii H and K line cores) decrease with stellar age t as 1/ t. With the advent of large photometric surveys, for example the Kepler mission, stellar photometric light curves have been measured for an extensive number of mainsequence stars This has allowed the determination of rotational periods for about thirty thousand stars (McQuillan et al 2013a,b; Reinhold et al 2013; Walkowicz & Basri 2013; Nielsen et al 2013; McQuillan et al 2014; do Nascimento et al 2014; García et al 2014; Reinhold & Gizon 2015; Ceillier et al 2016; Buzasi et al 2016). We analyse a sample of Kepler stars with near-solar values of effective temperature, photometric variability, and rotation periods, and compare the effect of metallicity on the detectability of rotational periods in observations and the theoretical model

Modelling

Analysis of Kepler observations

Findings

Conclusions