Cool stars like the Sun harbor convection zones capable of producing substantial surface
magnetic fields leading to stellar magnetic activity. The influence of stellar parameters like …

Aims. We investigate the magnetic field at the surface of 48 red giants selected as promising
for detection of Stokes V Zeeman signatures in their spectral lines. In our sample, 24 stars …

We aim to perform a statistical study of stellar flares observed by Kepler. We want to study
the flare amplitude, duration, energy, and occurrence rates, and how they are related to the …

Context. Betelgeuse is an M supergiant with a complex and extended atmosphere, which
also harbors spots and giant granules at its surface. A possible magnetic field could …

We present a flare catalog of the Kepler mission using the long-cadence data of Data
Release 25. This catalog comprises 3420 flare stars and 162,262 flare events. A comparison …

Active galactic nuclei with misaligned jets have been recently established as a class of high-
energy gamma-ray sources. M87, a nearby representative of this class, shows fast TeV …

Aims. We observe the nearby, weakly-active single giant, Pollux, in order to directly study
and infer the nature of its magnetic field. Methods. We used the new generation …

Aims. We observe the slowly-rotating, active, single giant, EK Eri, to study and infer the
nature of its magnetic field directly. Methods. We used the spectropolarimeter NARVAL at …

Aims. We study the fast rotating M 5 giant EK Boo by means of spectropolarimetry to obtain
direct and simultaneous measurements of both the magnetic field and activity indicators, in …

Aims. We have studied the active giant V390 Aur using spectropolarimetry to obtain direct
and simultaneous measurements of the magnetic field and the activity indicators to obtain a …