Related papers: Photometric observations from theoretical flip-flo…

Kepler-30 is a unique target to study stellar activity and rotation in a young solar-like star accompanied by a compact planetary system. We use about 4 years of high-precision photometry collected by the Kepler mission to investigate the…

Data from three solar observatories, Learmonth, Holloman, and San Vito, are used to study the variations in the average number of sunspots per sunspot group. It is found that the different types of sunspot groups and the number of sunspots…

The lower part of the classical instability strip and the surrounding main sequence are populated by a large variety of pulsating variable stars. In the past years a great effort was made by the stellar group of Brera Observatory to collect…

The beaming effect (aka Doppler boosting) induces a variation in the observed flux of a luminous object, following its observed radial velocity variation. We describe a photometric signal induced by the beaming effect during eclipse of…

We analyze the light curve of 1740 flare stars to study the relationship between the magnetic feature characteristics and the identified flare activity. Coverage and stability of magnetic features are inspired by rotational modulation of…

Light curves of young stars exhibit photometric variability over hours to decades and across a wide range of amplitudes. On time scales beyond a few rotation periods, these light curves are typically stochastic. The variability arises from…

We analyse light curves covering four years of 39 fast-rotating ($P_\mathrm{rot}< 1d$) late-type active stars from the Kepler database. Using time-frequency analysis (Short-Term Fourier-Transform), we find hints for activity cycles of…

The paper presents the results of the analysis of the geometric characteristics of sunspots for the period of 19-24 cycles of activity. The shape of sunspots was studied on the basis of the method of normalization of images of sunspots to…

Over the past century, the Sun's activity -- which exhibits significant variations -- went through a phase known as the Modern Maximum. Notably, the strongest sunspot cycle on record during this period, and indeed since direct sunspot…

Massive star winds are important contributors to the energy, momentum and chemical enrichment of the interstellar medium. Strong, organized and predominantly dipolar magnetic fields have been firmly detected in a small subset of massive…

New constraints on stellar models are provided by large surveys of massive stars, interferometric observations and asteroseismology. After a review of the main results so far obtained, we present new results from rotating models and discuss…

This chapter provides an overview of the magnetic activity of the Sun and stars, discussing its underlying physical origin, manifestations, and fundamental role in exoplanet studies. It begins with a summary of the Sun's magnetic activity…

Sunspots are cool areas caused by strong surface magnetic fields inhibiting convection. Moreover, strong magnetic fields can alter the average atmospheric structure, degrading our ability to measure stellar masses and ages. Stars more…

Synthetic observations are playing an increasingly important role across astrophysics, both for interpreting real observations and also for making meaningful predictions from models. In this review, we provide an overview of methods and…

Parameters of a special kind of \alpha-effect known in dynamo theory as the Babcock-Leighton mechanism are estimated using the data of sunspot catalogs. The estimates evidence the presence of the Babcock-Leighton \alpha-effect on the Sun.…

Observations of magnetic activity cycles in other stars provide a broader context for our understanding of the 11-year sunspot cycle. The discovery of short activity cycles in a few stars, and the recognition of analogous variability in the…

We study the tidal response of rotating solar mass stars, as well as more massive rotating stars, of different ages in the context of tidal captures leading to either giant exoplanets on close in orbits, or the formation of binary systems…

We present a method which provides some information on the possible binary nature on an appararently single star. The method compares the instantaneously measured HIPPARCOS proper motion with the long-term averaged, ground-based proper…

Context. Kepler-17 is a G2V sun-like star accompanied by a transiting planet with a mass of ~2.5 Jupiter masses and an orbital period of 1.486 d, recently discovered by the Kepler space telescope. This star is highly interesting as a young…

Until a few years ago, the amplitude variation in the photometric data had been limitedly explored mainly because of time resolution and photometric sensitivity limitations. This investigation is now possible thanks to the Kepler and CoRoT…