58 citations · 217 across the 13 of their papers we have counts for
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V889 Her: abrupt changes in the magnetic field or differential rotation?
Teemu Willamo, Thomas Hackman, Jyri J. Lehtinen +2
We have applied Zeeman-Doppler imaging (ZDI) to an extensive spectropolarimetric HARPSpol data set of the magnetically active young solar analogue V889 Her, covering 35 spectra obt…
Zeeman-Doppler imaging of five young solar-type stars
T. Willamo, J. J. Lehtinen, T. Hackman +5
The magnetic activity of the Sun changes with the solar cycle. Similar cycles are found in other stars as well, but their details are not known to a similar degree. Characterising…
Shapes of stellar activity cycles
T. Willamo, T. Hackman, J. J. Lehtinen +4
Magnetic activity cycles are an important phenomenon in both the Sun and other stars. The shape of the solar cycle is commonly characterised by a fast rise and a slower decline, bu…
Topological changes in the magnetic field of LQ Hya during an activity minimum
Jyri J. Lehtinen, Maarit J. Käpylä, Thomas Hackman +6
Previous studies have related surface temperature maps, obtained with the Doppler imaging (DI) technique, of LQ Hya with long-term photometry. We compare surface magnetic field map…
Starspot activity of HD 199178. Doppler images from 1994--2017
Thomas Hackman, Iya Ilyin, Jyri J. Lehtinen +4
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…
Long-term spot monitoring of the young solar analogue V889 Her
T. Willamo, T. Hackman, J. J. Lehtinen +6
Starspots are important manifestations of stellar magnetic activity. By studying their behaviour in young solar analogues, we can unravel the properties of their magnetic cycles. T…