Related papers: Possible chromospheric activity cycles in AD Leo
In a recent paper, we presented circularly polarized radio bursts detected by the radio telescope FAST from the flare star AD Leo on December 2-3, 2021, which were attributed to the electron cyclotron maser instability. In that context we…
HD 189733 is an exoplanetary system consisting of a transiting hot Jupiter and an active K2V-type main sequence star. We aim to use VLT/UVES high resolution echelle spectra to study a stellar flare. We have performed simultaneous analyses…
The young active flare star AU~Mic is the planet host star with the highest flare rate from TESS data. Therefore, it represents an ideal target for dedicated ground-based monitoring campaigns with the aim to characterize its numerous flares…
M dwarfs are prime targets for exoplanet searches due to their low masses and radii, which enable the detection of small planets in their habitable zones (HZs). However, the magnetic activity of M dwarfs can introduce signals in radial…
Direct comparison of high-resolution X-ray spectra of the active dMe star AD Leo, observed three times with Chandra, shows variability of key density-sensitive lines, possibly due to flaring activity. In particular, a significant…
We investigate the contribution of very weak flares to the coronal luminosity of low-mass active stars. We analyze EUVE/DS events data from FK Aqr, V1054 Oph, and AD Leo and conclude that in all these cases the coronal emission is dominated…
We present spectroscopic observations of two halo M subdwarfs which have H alpha emission lines. We show that in both cases close companions are the most likely cause of the chromospheric activity in these old, metal-poor stars. We argue…
We present optical spectroscopy of 710 solar neighborhood stars collected over twenty years to catalog chromospheric activity and search for stellar activity cycles. The California Legacy Survey stars are amenable to exoplanet detection…
Stellar flares affect all atmospheric layers from the photosphere over chromosphere and transition region up into the corona. Simultaneous observations in different spectral bands allow to obtain a comprehensive picture of the environmental…
The dynamo theory has always been one of the biggest mysteries in stellar physics. One key reason for its uncertainty is poor knowledge of the dynamo process on stars except the Sun. The most important observation feature of solar dynamo is…
Stellar flares are energetic events occurring in stellar atmospheres. They have been observed on various stars using photometric light curves and spectra. On some cool stars, flares tend to release substantially more energy compared to…
Obtaining observational evidence of the turbulent component of solar dynamo operating in the convective zone is a challenging problem because the dynamo action is hidden below the photosphere. Here we present results of a statistical study…
We present results from a model for magnetic flux generation and transport in cool stars and a qualitative comparison of models with observations. The method combines an alpha-omega dynamo at the base of the convection zone, buoyant rise of…
Stellar activity cycles reveal continuous relaxation and induction of magnetic fields. The activity cycle is typically traced through the observation of cyclic variations in total brightness or Ca H&K emission flux of stars, as well as…
Context: A variety of formation models for dwarf spheroidal (dSph) galaxies have been proposed in the literature, but generally they have not been quantitatively compared with observations. Aims: We search for chemodynamical patterns in our…
We conducted the time-resolved simultaneous optical spectroscopic and photometric observations of mid M dwarf flare stars YZ CMi, EV Lac, and AD Leo. Spectroscopic observations were obtained using Apache Point Observatory 3.5m and Small \&…
Flares are known to play an important role for the evolution of the atmospheres of young planets. In order to understand the evolution of planets, it is thus important to study the flare-activity of young stars. This is particularly the…
We have reanalyzed the long-term optical light curve (LC) of the symbiotic star Z Andromedae, covering 112--yr of mostly visual observations. Two strictly periodic and one quasi-periodic cycles can be identified in this LC. A P1=7550 d…
We study the Mount Wilson indices we obtained indirectly from IUE high and low resolution spectra of the RS CVn-type systems II Peg (K2IV), UX Ari (K0IV+G5V) and V711 Tau (K1IV+G5V), extensively observed by IUE from 1978 to 1996. We analyze…
By using the LAMOST time-domain survey data, we study stellar activities based on the $\rm{H_{\alpha}}$ lines for about 2000 stars in four $K$2 plates. Two indices, $R_{\rm{H\alpha}}^{'}$ and $R_{\rm{H\alpha}}^{+}$, are computed from LAMOST…