English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We present a catalogue of homogeneous determined chromospheric emission (CE),stellar atmospheric parameters and ages for 1,674 FGK main sequence (MS),subgiant, and giant stars. The analysis of CE level and variability is alsoperformed. We measured CE in the CaII lines using more than 180,000high-resolution spectra from the HARPS spectrograph, as compiled in the AMBREproject, obtained between 2003 and 2019. We converted the fluxes to bolometricand photospheric corrected chromospheric emission ratio, $R'_\text{HK}$.Stellar atmospheric parameters $T_\text{eff}$, $\log g$, and [Fe/H] wereretrieved from the literature or determined using an homogeneous method.$M_\star$, $R_\star$, and ages were determined from isochrone fitting. Weanalysed the CE distribution for the different luminosity classes and spectraltypes and confirmed the existence of the very inactive stars (VIS) and veryactive stars (VAS) populations at $\log R'_\text{HK}< -5.1$ and $> -4.2$ dex,respectively. We found indications that the VIS population is composed mainlyof subgiant and giant stars and that $\log R'_\text{HK}= -5.1$ dex marks atransition in stellar evolution. There appears to be at least three regimes ofvariability, for inactive, active and very active stars, with the inactive andactive regimes separated by a diagonal Vaughan-Preston gap. We show that starswith low activity levels do not necessarily have low variability. In the caseof K dwarfs which show high CE variability, inactive and active stars havesimilar levels of activity variability. This means that activity levels aloneare not enough to infer about the activity variability of a star. We alsoexplained the shape of the VP gap observed in the distribution of CE by usingthe CE variability-level diagram. In the CE variability-level diagram, the Sunis located in the high variability region of the inactive MS stars zone.(Abridged)

Stellar chromospheric activity of 1,674 FGK stars from the AMBRE-HARPS sample I. A catalogue of homogeneous chromospheric activity