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 the study on continuous high-resolution spectroscopic observationsof two long-period single-lined RS Canum Venaticorum (RS CVn) binary stars IMPegasi (IM Peg) and $\sigma$ Geminorum ($\sigma$ Gem), obtained with theHertzsprung SONG telescope during the 2015-2016 season. Chromospheric activityindicators H$_{\alpha}$, Na I D$_{1}$, D$_{2}$ doublet, He I D$_{3}$, andH$_{\beta}$ lines have been analyzed by using the spectral subtractiontechnique. The expected chromospheric emission features in the H$_{\alpha}$, NaI D$_{1}$, D$_{2}$ doublet, and H$_{\beta}$ lines confirm that both of twostars are very active systems. In the spectra, the He I D$_{3}$ line had beenalways detected in absorption feature. Although the behavior of chromosphericactivity indicators is very similar for both stars, the activity level of IMPeg is much stronger than that of $\sigma$ Gem. Moreover, the EW variations ofthe H$_{\alpha}$, He I D$_{3}$, and H$_{\beta}$ line subtractions correlatewell and show different behavior among different orbital cycles, whichindicates the presence and evolution of activity longitudes over the surface oftwo stars. Furthermore, the subtracted H$_{\alpha}$ line profile is usuallyasymmetric. The red-shifted excess absorption features could be interpreted asa strong down-flow of cool absorbing material, while the blue-shifted emissioncomponent is probably caused by up-flow of hot materials through microflareevents.

Magnetic activities on two single-lined RS Canum Venaticorum binaries IM Pegasi and $\sigma$ Geminorum