Related papers: Large Starspot Groups on HAT-P-11 in Activity Cycl…

We observed the Saturn-mass and Jupiter-sized exoplanet HAT-P-19b to refine its transit parameters and ephemeris as well as to shed first light on its transmission spectrum. We monitored the host star over one year to quantify its flux…

Observations of nine transits of WASP-107 during the {\it K2} mission reveal three separate occasions when the planet crossed in front of a starspot. The data confirm the stellar rotation period to be 17 days --- approximately three times…

We report the discovery of three new transiting extrasolar planets orbiting moderately bright (V=11.1 to 12.4) F stars. The planets have periods of P = 2.6940 d to 4.4572 d, masses of 0.60 M_J to 0.80 M_J, and radii of 1.57 R_J to 1.73 R_J.…

The signatures of planets hosted by M dwarfs are more readily detected with transit photometry and radial velocity methods than those of planets around larger stars. Recently, transit photometry was used to discover seven planets orbiting…

Transmission spectroscopy characterizes the wavelength dependence of transit depth, revealing atmospheric absorption features in planetary terminator regions. In this context, different optical transmission spectra of HAT-P-12b reported in…

In 2016, Kepler/K2 detected a system of two sub-Neptunes transiting the star HD 224018, one of them showing a mono-transit event. In 2017, we began a spectroscopic follow-up with HARPS-N to measure the dynamical masses of the planets using…

I briefly review the current state of the modelling of photospheric activity based on the high-precision optical light curves obtained with MOST, CoRoT, and Kepler. These models can be used to search for active longitudes where activity is…

Comet 12P/Pons-Brooks is a periodic comet with an orbital period of approximately 71 years. Because of the period duration, aphelion of 35.3 au, and highly inclined orbit (74.2 deg), it is classified as a Halley-type comet. In this work, we…

We announce the detection of recurring sets of recurring starspot occultation events in the short-cadence K2 lightcurve of Qatar-2, a K dwarf star transited every 1.34 d by a hot Jupiter. In total we detect 34 individual starspot…

Studying the properties of young planetary systems can shed light on how the dynamics and structure of planets evolve during their most formative years. Recent K2 observations of nearby young clusters (10-800 Myr) have enabled the discovery…

The outflows from comets in orbit around G-type main-sequence stars can be detected when they produce transient OH absorption lines in the spectrum near 3100 Angstroms of the host star. There is only about a 3 X 10^{-8} probability of…

Accurate and extensive photoelectric photometry has been obtained of V994 Her which was discovered as an eclipsing binary by Hipparcos satellite. A marked pulsation activity is evident in the light-curve, with periods 0.152100488,…

We present 10 new transit light curves of the transiting hot Jupiter HAT-P-13b, obtained during two observational seasons by three different telescopes. When combined with 12 previously published light curves, we have a sample consisting of…

HD144941 is an evolved early-type metal-poor low-mass star with a hydrogen-poor surface. It is frequently associated with other intermediate helium-rich subdwarfs and extreme helium stars. Previous photometric studies have failed to detect…

We describe a "super-Earth"-size ($2.30\pm0.15R_{\oplus}$) planet transiting an early K-type dwarf star in the Campaign 4 field observed by the K2 mission. The host star, EPIC 210363145, was identified as a member of the approximately…

KELT-11b is an inflated sub-Saturn with a hot atmosphere and that orbits a bright evolved subgiant star, making it a prime choice for atmospheric characterization, but that transits its host star for more than seven hours. We observed this…

We report the discovery and characterization of 7 transiting exoplanets from the HATNet survey. The planets, which are hot Jupiters and Saturns transiting bright sun-like stars, include: HAT-P-58b (with mass Mp = 0.37 MJ, radius Rp = 1.33…

Through our HARPS radial velocity survey for planets around solar twin stars, we have identified a promising Jupiter twin candidate around the star HIP11915. We characterize this Keplerian signal and investigate its potential origins in…

We report the discovery by the ground-based HATNet survey of the transiting exoplanet HAT-P-68b, which has a mass of 0.724 $\pm$ 0.043 $M_{Jup}$, and radius of 1.072 $\pm$ 0.012 $R_{Jup}$. The planet is in a circular P = 2.2984-day orbit…

Rapidly rotating giant stars are relatively rare and may represent important stages of stellar evolution, resulting from stellar coalescence of close binary systems or accretion of sub-stellar companions by their hosting stars. In the…