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M dwarfs are the most abundant stars in the Galaxy and exhibit diverse magnetic behaviours. Understanding their large-scale magnetic fields is essential to study stellar dynamos and assess the impact of magnetic activity on planetary…
Analyzing the available photometry from the Kepler satellite and other databases, we performed detailed light curve modeling of 10 eclipsing binary systems that were found to exhibit a periodic modulation of their orbital periods. All of…
We investigate the planetary transit detectability in the presence of stellar rotational activity from light curves for young M-dwarfs and estimate improvements of the detection at near-infrared (NIR) wavelengths. Making maps of the transit…
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…
A number of planet-host stars have been observed to rotate with a period equal to an integer multiple of the orbital period of their close planet. We expand this list by analyzing Kepler data of HAT-P-11 and finding a period ratio of 6:1.…
The Kepler Observatory offers unprecedented photometric precision (<1 mmag) and cadence for monitoring the central stars of planetary nebulae, allowing the detection of tiny periodic light curve variations, a possible signature of binarity.…
We conducted high dispersion spectroscopic observations of 50 superflare stars with Subaru/HDS. These 50 stars were selected from the solar-type superflare stars that we had discovered from the Kepler data. More than half (34 stars) of…
Even with the diminished precision possible with only two reaction wheels, the Kepler spacecraft can obtain mmag level, time-resolved photometry of tens of thousands of sources. The presence of such a rich, large data set could be…
We analyze light curves of 284,834 unique K2 targets using a Gaussian process model with a quasi-periodic kernel function. By crossmatching K2 stars to observations from Gaia Data Release 2, we have identified 69,627 likely main-sequence…
M dwarfs are prime targets in the hunt for habitable worlds around other stars. This is due to their abundance as well as their small radii and low masses and temperatures, which facilitate the detection of temperate, rocky planets in orbit…
We present rotation periods for 71 single dwarf members of the open cluster NGC6811 determined using photometry from NASA's Kepler Mission. The results are the first from The Kepler Cluster Study which combine Kepler's photometry with…
We present stellar rotation periods for late K- and early M-dwarf members of the 4 Gyr old open cluster M67 as calibrators for gyrochronology and tests of stellar spin-down models. Using Gaia EDR3 astrometry for cluster membership and…
Few observational constraints exist for the tidal synchronization rate of late-type stars, despite its fundamental role in binary evolution. We visually inspected the light curves of 2278 eclipsing binaries (EBs) from the Kepler Eclipsing…
We present period measurements of a large sample of field stars in the solar neighbourhood, observed by CoRoT in two different directions of the Galaxy. The presence of a period was detected using the Scargle Lomb Normalized Periodogram…
We observed stars with variable radial velocities to determine their spectroscopic orbits. Velocities of 132 targets taken over a time span reaching 30 years are presented. They were measured with the correlation radial velocity…
We investigate the variability properties of main sequence stars in the first month of Kepler data, using a new astrophysically robust systematics correction, and find that 60% of stars are more variable then the active Sun. We define low…
In the course of conducting a deep (14.5 ~< r ~< 23), 20 night survey for transiting planets in the rich ~550 Myr old open cluster M37 we have measured the rotation periods of 575 stars which lie near the cluster main sequence, with masses…
The CARMENES exoplanet survey of M dwarfs has obtained more than 18 000 spectra of 329 nearby M dwarfs over the past five years as part of its guaranteed time observations (GTO) program. We determine planet occurrence rates with the 71…
Magnetic chemically peculiar (mCP) stars allow the investigation of such diverse phenomena as atomic diffusion, magnetic fields and stellar rotation. The aim of the present investigation is to enhance our knowledge of the rotational…
A photometric monitoring campaign of brown dwarfs in the ChaI star forming region in the i and R band revealed significant periodic variations of the three M6.5-M7 type brown dwarf candidates ChaHa2, 3 and 6 (Joergens et al. 2002). These…