Context. Lithium abundance A(Li) and surface rotation are good diagnostic tools to probe the internal mixing and angular momentum transfer in stars. Aims. We explore the relation between surface rotation, A(Li), and age ...

We construct a finite analogue of classical Siegel's Space. This is made by generalizing Poincare half plane construction for a quadratic field extension E superset of F, considering in this case an involutive ring A, ...

Context. Solar-analogue stars provide an excellent resource to study the Sun’s evolution, i.e. the changes with time in stellar structure, activity, or rotation for solar-like stars. The unparalleled photometric data from ...

We construct a finite analogue of classical Siegel’s Space. This is made by generalizing Poincar´e half plane construction for a quadratic field extension E ⊃ F, considering in this case an involutive ring A, extension ...

Context. The detection of chromospheric activity cycles in solar-Analogue and twin stars can be used to place the solar cycle in a wider context. However, relatively few of these stars with activity cycles have been detected. ...

Context. Blue stragglers are easy to identify in globular clusters, but are much harder to identify in the field. Here we present the serendipitous discovery of one field blue straggler, HIP 10725, that closely matches the ...

We computed chromospheric models of the Sun as a star and of nine solar analogues. The atmospheric models were constructed to obtain the best possible match with the Ca II K and Hβ lines, including the asymmetry of the ...

Long-term stellar activity variations can affect the detectability of long-period and Earth-analogue extrasolar planets. We have, for 54 stars, analysed the long-term trend of five activity indicators: logR HK, the ...

The source of energetic photons that heated and reionized the early Universe emains uncertain. Early galaxies had low metallicity and recent population synthesis calculations suggest that the number and luminosity of ...

We perform, for the first time, a detailed long-term activity study of the binary system ζ Ret. We use all available HARPS spectra obtained between the years 2003 and 2016. We build a time series of the Mount Wilson S index ...