Related papers: Multiwavelength optical observations of two chromo…
CONTEXT: Accurate mass, radius, and abundance determinations from binaries provide important information on stellar evolution, fundamental to central fields in modern astrophysics and cosmology. AIMS: Within the long-term Copenhagen Binary…
We report the results of our radial-velocity monitoring of spectroscopic binary systems in a sample of X-ray sources from the ROSAT All Sky Survey south of the Taurus-Auriga star-forming region. The original sample of approximately 120…
We apply the variational autoencoder (VAE) to the LAMOST-K2 low-resolution spectra to detect the magnetic activity of the stars in the K2 field. After the training on the spectra of the selected inactive stars, the VAE model can efficiently…
The unparalleled photometric data obtained by NASA's Kepler Space Telescope has led to an improved understanding of stellar structure and evolution - in particular for solar-like oscillators in this context. Binary stars are fascinating…
We analyze two binary systems containing giant stars, V723 Mon ("the Unicorn") and 2M04123153+6738486 ("the Giraffe"). Both giants orbit more massive but less luminous companions, previously proposed to be mass-gap black holes. Spectral…
Firstly, we review the stellar chromospheric activity in the optical wavelength. Secondly, we introduce our ongoing project of multi-wavelength high--resolution optical observations aimed at studying the chromospheric activity of different…
We report the results of a pilot study that searched for dual active galactic nuclei (AGN) in local ($z<$0.25) galaxies hosting double-peaked narrow emission lines in their optical spectra. We present high-resolution $L-$band (1.5 GHz or 18…
We present results from a high-angular-resolution survey of 78 very low mass (VLM) binary systems with 6.0 <= V-K colour <= 7.5 and proper motion >= 0.15 arcsec/yr. 21 VLM binaries were detected, 13 of them new discoveries. The new binary…
We have examined the relationship between rotation and activity in 14 late-type (M6-M7) M dwarfs, using high resolution spectra taken at the W.M. Keck Observatory and flux-calibrated spectra from the Sloan Digital Sky Survey. Most were…
The A-type star HR 6412 = V2368 Oph was used by several investigators as a photometric comparison star for the known eclipsing binary U Oph but was found to be variable by three independent groups, including us. By analysing series of new…
Chromospherically Active Binaries (CAB) catalogue have been revised and updated. With 203 new identifications, the number of CAB stars is increased to 409. Catalogue is available in electronic format where each system has various number of…
We investigate the relationship between age and chromospheric activity for 139 M dwarf stars in wide binary systems with white dwarf companions. The age of each system is determined from the cooling age of its white dwarf component. The…
We derive single-epoch radial velocities for a sample of 56 B-type stars members of the subgroups Upper Scorpius, Upper Centaurus Lupus and Lower Centaurus Crux of the nearby Sco-Cen OB association. The radial velocity measurements were…
M-type stars are crucial for stellar activity studies since they cover two types of magnetic dynamos and particularly intriguing for habitability studies due to their abundance and long lifespans during the main-sequence stage. In this…
The masses of compact objects in X-ray binaries are best constrained through dynamical measurements, relying on radial velocity curves of the companion star. In anticipation of upcoming high X-ray spectral resolution telescopes, we explore…
Since early 2015 a new radial velocity monitoring campaign is going on at the University Observatory Jena. The aim of this project is to obtain current radial velocity measurements of selected single-lined spectroscopic binary systems, to…
Eclipsing binaries provide a unique opportunity to determine fundamental stellar properties. In the era of wide-field cameras and all-sky imaging surveys, thousands of eclipsing binaries have been reported through light curve…
This work is part of an ongoing project which aims to detect terrestrial planets in our neighbouring star system $\alpha$ Centauri using the Doppler method. Owing to the small angular separation between the two components of the $\alpha$…
Light curves of microlensing events involving stellar binaries and planetary systems can provide information about the orbital elements of the system due to orbital modulations of the caustic structure. Accurately measuring the orbit in…
We present a first and detailed study of the bright and active K0IV-III star HD 123351. The star is found to be a single-lined spectroscopic binary with a period of 147.8919+-0.0003 days and a large eccentricity of e=0.8086+-0.0001. The rms…