Related papers: $\zeta^{1} + \zeta^{2}$ Reticuli binary system: A …
After decades of effort, the solar activity cycle is exceptionally well characterized but it remains poorly understood. Pioneering work at the Mount Wilson Observatory demonstrated that other sun-like stars also show regular activity…
RZ Cas is a short-period Algol-type system showing episodes of mass transfer and Delta Sct-like oscillations of its mass-gaining primary component. We analyse high-resolution spectra of RZ Cas that we obtained during a spectroscopic…
A comprehensive multi-wavelength campaign has been carried out to probe stellar activity and variability in the young Sun-like star $\iota$-Horologii. We present the results from long-term spectropolarimetric monitoring of the system by…
A number of planet-host stars have been observed to rotate with a period equal to an integer multiple of the orbital period of their close planet. We expand this list by analyzing Kepler data of HAT-P-11 and finding a period ratio of 6:1.…
Multiband CCD photometric observations of SZ Her were obtained between 2008 February and May. The light curve was completely covered and indicated a significant temperature difference between both components. The light-curve synthesis…
We present five decades of chromospheric activity measurements in 59 Sun-like stars as time series. These include and extend the 35 yr of stellar chromospheric activity observations by the Mount Wilson Survey (1966--2001), and continued…
In a search of proper motion catalogs for common proper motion stars in the field of the Kepler spacecraft I identified 93 likely binary systems. A comparison of their rotation periods is a test of the gyrochronology concept. To find their…
(Abridged) Most stellar activity cycles similar to that found in the Sun have been detected by using the chromospheric Ca II H&K lines as stellar activity proxies. However, it is unclear if such activity cycles could be identified using…
We present a catalog of binary companions to $\delta$ Scuti stars, detected through phase modulations of their pulsations in TESS data. Pulsation timing has provided orbits for hundreds of pulsating stars in binaries from space-based…
M stars are ideal targets to search for Earth-like planets. However, they usually have high levels of magnetic activity, which could affect their habitability and make difficult the detection of exoplanets orbiting around them.…
A number of binary systems present evidence of enhanced activity around periastron passage, suggesting a connection between tidal interactions and these periastron effects. The aim of this investigation is to study the time-dependent…
The Sun has a steady 11-year cycle in magnetic activity most well-known by the rising and falling in the occurrence of dark sunspots on the solar disk in visible bandpasses. The 11-year cycle is also manifest in the variations of emission…
This paper describes a multiwavelengh optical study of chromospheres in two X-ray/EUV selected active binary stars with strong H_alpha emission, V789 Mon (2RE J0725-002) and GZ Leo (2RE J1101+223). The goal of the study is to determine…
We have used two robotic telescopes to obtain time-series high-resolution spectroscopy and V I and/or by photometry for a sample of 60 active stars. Orbital solutions are presented for 26 SB2 and 19 SB1 systems with unprecedented phase…
We report the discovery of a new planetary system around the K giant $\eta$ Cet (HIP 5364, HD 6805) based on 118 high-precision optical radial velocities taken at Lick Observatory since July 2000. Since October 2011 an additional nine…
(Abridged) We perform a detailed study of the main optical activity indicators (Ca II H & K, Balmer lines, Na I D$_{\rm 1}$ D$_{\rm 2}$, and He I D$_{\rm 3}$) measured for the Sun using the data provided by the HARPS-N solar-telescope feed…
In a recent study, Lee et al. presented new photometric follow-up timing observations of the semi-detached binary system SZ Herculis and proposed the existence of two hierarchical cirumbinary companions. Based on the light-travel time…
Spectroscopic analyses of young late-type stars suffer from systematic inaccuracies, typically under-estimating metallicities but over-estimating abundances of certain elements including oxygen and barium. Effects are stronger in younger…
The temporal analysis of stellar activity evolution is usually dominated by a complex trade-off between model complexity and interpretability, often by neglecting the non-stationary nature of the process. Recent studies appear to indicate…
Oscillating stars in binary systems are among the most interesting stellar laboratories, as these can provide information on the stellar parameters and stellar internal structures. Here we present a red giant with solar-like oscillations in…