Time evolution of high-energy emissions of low-mass stars:I. Age determination using stellar chronology with white dwarfs in wide binaries

TL;DR

This study calibrates the decline of high-energy emissions in low-mass stars over time using white dwarf cosmochronology in wide binaries, enabling more accurate age estimates for stars aged 1-5 Gyr, which is crucial for understanding exoplanetary atmospheres.

Contribution

It introduces a method to determine stellar ages using white dwarf companions in wide binaries, improving age estimates for low-mass stars beyond 1 Gyr.

Findings

Reliable ages for 27 stars between 1 and 5 Gyr were obtained.

White dwarf cosmochronology effectively estimates ages where traditional methods struggle.

The method enhances understanding of high-energy emission evolution in low-mass stars.

Abstract

Stellar ages are extremely difficult to determine and often subject to large uncertainties, especially for field low-mass stars. We plan to carry out a calibration of the decrease in high-energy emissions of low-mass GKM stars with time, and therefore precise age determination is a key ingredient. The overall goal of our research is to study the time evolution of these high-energy emissions as an essential input to studing exoplanetary atmospheres. We propose to determine stellar ages with a methodology based on wide binaries. We are interested in systems composed of a low-mass star and a white dwarf (WD), where the latter serves as a stellar chronometer for the system. We aim at obtaining reliable ages for a sample of late-type stars older than 1 Gyr. We selected a sample of wide binaries composed by a DA type WD and a GKM companion. High signal-to-noise, low-resolution spectroscopic observations were obtained for most of the WD members of the sample. Atmospheric parameters were determined by fitting the spectroscopic data to appropiate WD models. The total ages of the systems were derived by using cooling sequences, an initial-final mass relationship and evolutionary tracks, to account for the progenitor life. The spectroscopic observations have allowed us to determine ages for the binary systems using WDs as cosmochronometers. We obtained reliable ages for 27 stars between 1 and 5 Gyr, which is a range where age determination becomes difficult for field objects.