The discontinuous nature of chromospheric activity evolution

TL;DR

This paper challenges the traditional view that chromospheric activity decays smoothly with age, presenting evidence that it undergoes a rapid transition around 1 Gyr, making it a less reliable age indicator before or after this period.

Contribution

It reveals the discontinuous nature of chromospheric activity evolution, highlighting a sudden transition rather than a gradual decay in solar-type stars.

Findings

Chromospheric activity transitions rapidly after about 1 Gyr.

Short-term variations dominate over any gradual decay trend.

The transition challenges the use of activity as a smooth age indicator.

Abstract

Chromospheric activity has been thought to decay smoothly with time and, hence, to be a viable age indicator. Measurements in solar type stars in open clusters seem to point to a different conclusion: chromospheric activity undergoes a fast transition from Hyades level to that of the Sun after about 1 Gyr of main--sequence lifetime and any decaying trend before or after this transition must be much less significant than the short term variations.