Related papers: Strong variable linear polarization in the cool ac…
Magnetic fields in cool stars are ubiquitous but can still be challenging to characterize due to their complexity and relatively low strength. The polarization signature amplitudes are proportional to the field strength, and current studies…
Magnetic fields are ubiquitous in active cool stars but they are in general complex and weak. Current Zeeman Doppler imaging (ZDI) studies of cool star magnetic fields chiefly employ circular polarization observations because linear…
The dynamo processes in cool active stars generate complex magnetic fields responsible for prominent surface stellar activity and variability at different time scales. For a small number of cool stars magnetic field topologies were…
The application of high-resolution spectropolarimetry has led to major progress in understanding the magnetism and activity of late-type stars. During the last decade, magnetic fields have been discovered and mapped for many types of active…
We present a temperature and a magnetic-field surface map of the K2 subgiant of the active binary II Peg. Employed are high resolution Stokes IV spectra obtained with the new Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI)…
We report on the first ever detection of circular polarization in molecular lines forming in magnetic regions on the surfaces of active stars. The new observations were obtained with the high-resolution spectropolarimeter ESPaDOnS recently…
We present BVR polarimetric study of the cool active star LO Peg for the first time. LO Peg was found to be highly polarized among the cool active stars. Our observations yield average values of polarization in LO Peg: $P_B =0.387\pm…
Magnetic fields of cool stars can be directly investigated through the study of the Zeeman effect on photospheric spectral lines using several approaches. With spectroscopic measurement in unpolarised light, the total magnetic flux averaged…
Here we report on the first detection of circular polarization in molecular lines formed in cool magnetic regions (starspots) and in chromospheric emission lines formed in hot plages on the surfaces of active stars. Our survey of G-K-M…
The goal of this work is to study the cool, active binary star $\sigma^2$ CrB, focussing on its magnetic field. We used Stokes $IV$ data from the twin spectropolarimeters Narval at the TBL and ESPaDOnS at the CFHT. The least-squares…
A method for the determination of integrated longitudinal stellar fields from low-resolution spectra is the so-called slope method, which is based on the regression of the Stokes V signal against the first derivative of Stokes I. Here we…
Classical Cepheids are essential objects in the study of stellar evolution and cosmology; however, we know little about their magnetic properties. We report the detection of Stokes $V$ features interpreted as Zeeman signatures in four…
We publish 16 Doppler imaging temperature maps for the years 1994-2002 of the active RS CVn star II Peg. The six maps from 1999-2002 are based on previously unpublished observations. Through Doppler imaging we want to study the spot…
We present preliminary results from a programme aimed at acquiring linear spectropolarimetry of magnetic A and B stars. Linear polarization in the spectral lines of these objects is due to the Zeeman effect, and should provide detailed new…
Late-type stars in general possess complicated magnetic surface fields which makes their detection and in particular their modeling and reconstruction challenging. In this work we present a new Zeeman-Doppler imaging code which is…
By studying young magnetically active late-type stars, i.e. analogues to the young Sun, one can draw conclusions on the evolution of the solar dynamo. We determine the topology of the surface magnetic field and study the relation between…
We present a new implementation of the magnetic Doppler imaging technique, which aims at self-consistent temperature and magnetic mapping of the surface structures in cool active stars. Our magnetic imaging procedure is unique in its…
Aims. We study the spot activity of II Peg during the years 2004-2010 to determine long- and short-term changes in the magnetic activity. In a previous study, we detected a persistent active longitude, as well as major changes in the spot…
We report recent ESPaDOnS and HARPSpol spectropolarimetric observations from our ongoing magnetic survey of the brightest twenty-five classical Cepheids. Stokes $V$ magnetic signatures are detected in eight of fifteen targets observed to…
The large-scale magnetic field of solar-type stars reconstructed from their spectropolarimetric observations provide important insight into their underlying dynamo processes.We aim to investigate the temporal variability of the large-scale…