Related papers: LO Peg in 1998: Starspot patterns and differential…
The observed amplitude of the rotational photometric modulation of a star with spots should depend on the inclination of its rotational axis relative to our line of sight. Therefore, the distribution of observed rotational amplitudes of a…
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 variation of the magnetic field over the rotational period of…
V889 Herculis is one of the brightest single early-G type stars, a young Sun, that is rotating fast enough (P_rot =1.337 days) for mapping its surface by Doppler Imaging. The 10 FOCES spectra collected between 13-16 Aug 2006 at Calar Alto…
Aims: We aim to measure the starspot rotation periods of active stars in the Kepler field as a function of spectral type and to extend reliable rotation measurements from F-, G-, and K-type to M-type stars. Methods: Using the Lomb-Scargle…
We study the short-term evolution of starspots on the ultrafast-rotating star HD197890 ("Speedy Mic" = BO Mic, K 0-2V, P_rot = 0.380 d) based on two Doppler images taken about 13 stellar rotations apart. Each image is based on spectra…
The CoRoT space telescope observed nearly 160 000 light curves. Among the most outstanding is that of the young, active planet host star CoRoT-2A. In addition to deep planetary transits, the light curve of CoRoT-2A shows strong rotational…
We use high accuracy photometric data obtained with the Kepler satellite to monitor the activity modulations of the Kepler-210 planet host star over a time span of more than four years. Following the phenomenology of the star's light curve…
Starspots and their movements on stellar surfaces enable investigating the mechanisms of stellar magnetic activity. Information on the spot distribution and differential rotation provide important constraints for the behaviour of stellar…
Starspots are cooler and darker than the stellar surface. Therefore, the emitted flux of a star changes when spots are visible on its surface. The presence of spots together with the stellar rotation leads to a periodic modulation on the…
CoRoT-2, the second planet-hosting star discovered by the CoRoT satellite, is a young and active star. A total of 77 transits were observed for this system over a period of 135 days. Small modulations detected in the optical light curve of…
Surface brightness maps for the young K0 dwarf AB Doradus are reconstructed from archival data sets for epochs spanning 1988 to 1994. By using the signal-to-noise enhancement technique of Least-Squares Deconvolution, our results show a…
The Hubble Space Telescope (HST) and the Kepler space mission observed a large number of planetary transits showing anomalies due to starspot eclipses, with more such observations expected in the near future by the K2 mission and the…
The present study reports the discovery of Sun-like stars, namely main-sequence stars with $T_{\rm eff}$, $\log g$ and rotation periods $P_{rot}$ similar to solar values, presenting evidence of surface differential rotation. An…
We have detected modulation of the Ca II H&K reversal structure in four out of five 51 Peg-type stars whose planets have orbital periods between 3 and 4 days. We observe two effects in the K-core: (1) a broad 3-A variation at ~1% level and…
Starspots trace stellar magnetic activity and influence both stellar evolution and exoplanet characterization. While occultation-based spot analyses have been applied to individual systems, comparative studies remain limited. We apply the…
We report the latest view of Kepler solar-type (G-type main-sequence) superflare stars, including recent updates with Apache Point Observatory (APO) 3.5m telescope spectroscopic observations and Gaia-DR2 data. First, we newly conducted…
We measure rotation periods for 12151 stars in the Kepler field, based on the photometric variability caused by stellar activity. Our analysis returns stable rotation periods over at least six out of eight quarters of Kepler data. This…
Dark magnetic spots crossing the stellar disc lead to quasi-periodic brightness variations, which allow us to constrain stellar surface rotation and photometric activity. The current work is the second of this series (Santos et al. 2019;…
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 a new method for tracking the phases of the orbital modulations in very short-period, near-contact, and contact binary systems systems in order to follow starspots. We apply this technique to Kepler light curves for 414 binary…