The extreme ultraviolet and X-ray Sun in Time: High-energy evolutionary tracks of a solar-like star

¹ Department of AstrophysicsUniversity of Vienna, Türkenschanzstrasse 17, 1180 Vienna, Austria
e-mail: lin.tu@univie.ac.at; colin.johnstone@univie.ac.at; manuel.guedel@univie.ac.at
² Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, 8042 Graz, Austria
e-mail: helmut.lammer@oeaw.ac.at

Received: 20 March 2015
Accepted: 17 April 2015

Abstract

Aims. We aim to describe the pre-main-sequence and main-sequence evolution of X-ray and extreme-ultaviolet radiation of a solar-mass star based on its rotational evolution starting with a realistic range of initial rotation rates.

Methods. We derive evolutionary tracks of X-ray radiation based on a rotational evolution model for solar-mass stars and the rotation-activity relation. We compare these tracks to X-ray luminosity distributions of stars in clusters with different ages.

Results. We find agreement between the evolutionary tracks derived from rotation and the X-ray luminosity distributions from observations. Depending on the initial rotation rate, a star might remain at the X-ray saturation level for very different time periods, from ≈10 Myr to ≈300 Myr for slow and fast rotators, respectively.

Conclusions. Rotational evolution with a spread of initial conditions leads to a particularly wide distribution of possible X-ray luminosities in the age range of 20–500 Myr, before rotational convergence and therefore X-ray luminosity convergence sets in. This age range is crucial for the evolution of young planetary atmospheres and may thus lead to very different planetary evolution histories.