Related papers: Magnetic activities on active solar-type stars
The solar active region NOAA 11719 produced a large two-ribbon flare on 11 April 2013. We have investigated the sudden variations in the photospheric magnetic fields in this active region during the flare employing the magnetograms obtained…
The fraction of low-mass (LM) stars (M <= 1.5 Msun) showing photospheric activity in their light curve is larger on the horizontal branch (HB) than during the previous red giant branch (RGB) phase, while the opposite trend has been observed…
We present results of an asteroseismic study on the $\gamma$ Dor type {\it Kepler} target KIC\,6462033. {\it Kepler} photometry is used to derive the frequency content and principal modes. High-dispersion ground-based spectroscopy is also…
We present an investigation of the magnetic activity and flare characteristics of the sub-giant stars mostly from F and G spectral types and compare the results with the main-sequence (MS) stars. The light curve of 352 stars on the…
The 11-year activity cycle of the Sun is a consequence of a dynamo process occurring beneath its surface. We analyzed photometric data obtained by the CoRoT space mission, showing solar-like oscillations in the star HD49933, for signatures…
Radio observations at low frequencies are sensitive to the magnetic activity of stars and the plasma environment surrounding them. The accurate interpretation of the processes underlying the radio signatures requires a detailed…
Using precise measurements of the helium D3 line, we have searched for statistically significant variations in the strength of chromospheric activity in 13 early F-type stars and two late F-type stars. In two early F-type stars, we find…
Flare flux reflect contribution from active regions rather than the whole hemisphere of a star. Unlike the amplitude of light-curves caused by starspots, the flare detection is independent of inclination. The two valuable properties of…
We have acquired high-resolution echelle spectra of 225 F6-M5 type stars in the southern hemisphere. The stars are targets or candidates to be targets for the Anglo-Australian Planet Search. CaII HK line cores were used to derive activity…
The NASA Kepler mission is providing an unprecedented set of asteroseismic data. In particular, short-cadence lightcurves (~60s samplings), allow us to study solar-like stars covering a wide range of masses, spectral types and evolutionary…
This study explores photometric variability in a sample of hot stars in order to test whether variability arises from rotational modulation due to surface temperature spots. Frequencies determined from the projected rotational velocities…
In many active stars the spots concentrate on two permanent active longitudes which are 180 degrees apart. In some of these stars the dominant part of the spot activity changes the longitude every few years. This so-called flip-flop…
Understanding the relationship between the magnetic field and coronal heating is one of the central problems of solar physics. However, studies of the magnetic properties of impulsively heated loops have been rare. We present results from a…
Understanding magnetic activity on the surface of stars other than the Sun is important for exoplanet analyses to properly characterize an exoplanet's atmosphere and to further characterize stellar activity on a wide range of stars.…
Stellar activity is fundamental to stellar evolution and the formation and habitability of exoplanets. The interaction between convective motions and rotation in cool stars results in a dynamo process that drives magnetic surface activity.…
Our understanding of the impact of magnetic activity on stellar evolution continues to unfold. This impact is seen in sub-subgiant stars, defined to be stars that sit below the subgiant branch and red of the main sequence in a cluster…
Context. Young, solar analogue stars provide key insights into the early stages of stellar evolution, particularly in terms of magnetic activity and rotation. Their rapid rotation, high flaring rate, and enhanced surface activity make them…
According to earlier Doppler images of the magnetically active primary giant component of the RS CVn binary II Peg, the surface of the star was dominated by one single active longitude that was clearly drifting in the rotational frame of…
Context: Chromospheric activity produces both photometric and spectroscopic variations that can be mistaken as planets. Large spots crossing the stellar disc can produce planet-like periodic variations in the light curve of a star. These…
In this publication we present a study of the general physical, chemical properties and radial velocity monitoring of young active stars. We derive temperatures, log g, [Fe/H], v sin i, and R_{spec} values for eight stars. The detailed…