102 citations · 531 across the 21 of their papers we have counts for
21 papers
Estimating activity cycles with probabilistic methods II. The Mount Wilson Ca H&K data
N. Olspert, J. Lehtinen, M. J. Käpylä +2
Debate over the existence of branches in the stellar activity-rotation diagrams continues. Application of modern time series analysis tools to study the mean cycle periods in chrom…
Estimating activity cycles with probabilistic methods I. Bayesian Generalised Lomb-Scargle Periodogram with Trend
N. Olspert, J. Pelt, M. J. Käpylä +1
Period estimation is one of the central topics in astronomical time series analysis, where data is often unevenly sampled. Especially challenging are studies of stellar magnetic cy…
Method of frequency dependent correlations: investigating the variability of total solar irradiance
Jaan Pelt, Maarit Käpylä, Nigul Olspert
This paper contributes to the field of modeling and hindcasting of the total solar irradiance (TSI) based on different proxy data that extend further back in time than the TSI that…
Multiperiodicity, modulations and flip-flops in variable star light curves III. Carrier fit analysis of LQ Hya photometry for 1982-2014
Nigul Olspert, Maarit J. Käpylä, Jaan Pelt +4
We study LQ Hya photometry for 1982-2014 with the carrier fit (CF) -method and compare our results to earlier photometric analysis and recent Doppler imaging maps. We first utilize…
Magnetically controlled stellar differential rotation near the transition from solar to anti-solar profiles
Bidya Binay Karak, Petri J. Kapyla, Maarit J. Kapyla +3
Late-type stars rotate differentially owing to anisotropic turbulence in their outer convection zones. The rotation is called solar-like (SL) when the equator rotates fastest and a…
Multiperiodicity, modulations and flip-flops in variable star light curves II. Analysis of II Peg photometry during 1979-2010
Marjaana Lindborg, Maarit J. Mantere, Nigul Olspert +5
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 longi…