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Radial differential rotation vs surface differential rotation: investigation based on dynamo models
H. Korhonen, D. Elstner
Differential rotation plays a crucial role in the alpha-omega dynamo, and thus also in creation of magnetic fields in stars with convective outer envelopes. Still, measuring the ra…
First measurement of the magnetic field on FK Com and its relation to the contemporaneous starspot locations
H. Korhonen, S. Hubrig, S. V. Berdyugina +5
In this study we present simultaneous low-resolution longitudinal magnetic field measurements and high-resolution spectroscopic observations of the cool single giant FK Com. The va…
Photospheric and chromospheric activity on EY Dra
H. Korhonen, K. Brogaard, K. Holhjem +4
Magnetic activity in the photosphere and chromosphere of the M dwarf EY Dra is studied and possible correlations between the two are investigated using photometric observations in…
Photometric observations from theoretical flip-flop models
H. Korhonen, D. Elstner
Some active stars show a so-called flip-flop phenomenon in which the main spot activity periodically switches between two active longitudes that are 180 degrees apart. In this pape…
Flip-flop phenomenon: observations and theory
D. Elstner, H. Korhonen
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…
The time delay of the quadruple quasar RX J0911.4+0551
Jens Hjorth, Ingunn Burud, Andreas O. Jaunsen +9
We present optical lightcurves of the gravitationally lensed components A (=A1+A2+A3) and B of the quadruple quasar RX J0911.4+0551 (z = 2.80). The observations were primarily obta…