Related papers: Analysing the active longitudes of the young solar…
We formulate an improved time series analysis method for the analysis of photometry of active stars. This new Continuous Period Search (CPS) method is applied to 12 years of V band photometry of the young solar analogue HD 116956 (NQ UMa).…
We study a sample of 21 young and active solar-type stars with spectral types ranging from late F to mid K and characterize the behaviour of their activity. We apply the continuous period search (CPS) time series analysis method on 16 to 27…
We investigate the spot activity of the young chromospherically active main sequence star LQ Hya. Our aims are to identify possible active longitudes, estimate the differential rotation and study long and short term changes in the activity.…
We present photometry and spectropolarimetry of the pre-main sequence star HD 106506. A photometric rotational period of ~1.416 +/- 0.133 days has been derived using observations at Mount Kent Observatory (MKO). Spectropolarimetric data…
Stellar spot distribution has consequences on the observable periodic signals in long-time baseline ground-based photometry. We model the statistics of the dominating spots of two young and active Solar-type stars, V889 Her and LQ Hya, in…
Aims: We carried out high-resolution spectroscopy and BV(I)_C photometric monitoring of the two fastest late-type rotators in the nearby Beta Pictoris moving group, HD199143 (F7V) and CD-641208 (K7V). The motivation for this work is to…
The temporal behaviour of solar active longitudes has been examined by using two sunspot catalogues, the Greenwich Photoheliographic Results (GPR) and the Debrecen Photoheliographic Data (DPD). The time-longitude diagrams of the activity…
Context. Studying the spots of late-type stars is crucial for distinguishing between the various proposed dynamo mechanisms believed to be the main cause of starspot activity. For this research it is important to collect observation time…
The new photometric data on pulsating Ap star HD~27463 obtained recently with the Transiting Exoplanet Survey Satellite (\textit{TESS}) are analysed to search for variability. Our analysis shows that HD~27463 exhibits two types of…
A growing body of evidence suggests that multiple dynamo mechanisms can drive magnetic variability on different timescales, not only in the Sun but also in other stars. Many solar activity proxies exhibit a quasi-biennial ($\sim$2 year)…
As recently found, the distribution of sunspots is non-axisymmetric and spot group formation implies the existence of two persistent active longitudes separated by 180 degrees. Here we quantitatively study the non-axisymmetry of sunspot…
The sunspots and other solar activity indicators tend to cluster on the surface of the Sun.These clusters very often occur at certain longitudes that persist in time.It is of general interest to find new and simple ways to characterize the…
We present the results of contemporaneous spectroscopic and photometric monitoring of the young solar-type star HD171488 (Prot~1.337 d) aimed at studying surface inhomogeneities at photospheric/chromospheric levels. Echelle FOCES spectra…
We analyze systematics in the asteroseismological mass determination methods in pulsating PG 1159 stars. We compare the seismic masses resulting from the comparison of the observed mean period spacings with the usually adopted asymptotic…
We detect the second known lambda Bootis star (HD 54272) which exhibits gamma Doradus-type pulsations. The star was formerly misidentified as a RR Lyrae variable. The lambda Bootis stars are a small group (only 2 per cent) of late B to…
Context. The CoRoT short runs give us the opportunity to observe a large variety of late-type stars through their solar-like oscillations. We report observations of the star HD175726 that lasted for 27 days during the first short run of the…
(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…
Stellar activity induces apparent radial velocity (RV) variations in late-type main-sequence stars that may hamper the detection of low-mass planets and the measurement of their mass. We use simultaneous measurements of the active planet…
We present analysis of the starspot properties and chromospheric activity on HD 134319 using high precision photometry by TESS in sectors 14-16 (T1), 21-23 (T2) and high-resolution spectroscopy by OHP/ELODIE and Keck/HIRES during years…
We introduce a method of measuring a lower limit to the amplitude of surface differential rotation from high-precision, evenly sampled photometric time series. It is applied to main-sequence late-type stars whose optical flux modulation is…