Related papers: The Variability of Halpha Equivalent Widths in Be …
Multi-epoch photometry from AllWISE provides the opportunity to investigate variability at 3.4 and 4.6 microns for most known brown dwarfs. WISE observed the same patch of sky repeatedly and within a day's time, roughly 12 observations were…
The comparison of different atomic transition frequencies over time can be used to determine the present value of the temporal derivative of the fine structure constant alpha in a model-independent way without assumptions on constancy or…
Activities in M dwarfs show spectroscopic variability over various time scales ranging from a few seconds to several hours. The time scales of such variability can be related to internal dynamics of M dwarfs like magnetic activity,…
A new method for examining the possible space-time variation of the fine structure constant ($\alpha$) is proposed. The technique uses a relatively simple measurement with an optical resonator to compare atom-stabilized optical frequency…
Astronomical data are typically irregular in time, e.g. the space (HIPPARCOS/TYCHO, KEPLER, GAIA, WISE etc.) and ground-based CCD (NSVS, ASAS, CRTS, SuperWASP etc.) and photographic (Harvard, Sonneberg, Odessa etc.) photometrical surveys.…
Galactic field Be stars were studied by taking into account the effects induced by the fast rotation on their fundamental parameters. Fractional ages $\tau/\tau\_{\rm MS}$ ($\tau\_{\rm MS}$ = time spent in the MS) against stellar mass…
Current state of the variable stars studies, including halo and globular-cluster variables is briefly discussed, as well as the halo kinematics and modern problems of the Universal distance scale. I propose new approach to the projection…
Measurements of the total amount of stars locked up in galaxies as a function of host halo mass contain key clues about the efficiency of processes that regulate star formation. We derive the total stellar mass fraction f_star as a function…
We present multiple epochs of near-IR spectroscopy for a sample of 25 young stars, including T Tauri, Herbig Ae/Be, and FU Ori objects. Using the FSPEC instrument on the Bok 90-inch telescope, we obtained K-band spectra of the BrGamma…
By measuring the fundamental constants in astrophysical objects one can test basic physical principles as space-time invariance of physical laws along with probing the applicability limits of the standard model of particle physics. The…
We have studied a sample of 28 periodically variable B-type supergiants selected from the HIPPARCOS mission and 12 comparison stars covering the whole B-type spectral range. Our goal is to test if their variability is compatible with…
We report on optical high-dispersion spectroscopic monitoring observations of the Be/X-ray binary A0535+26/V725 Tau, carried out from November 2005 to March 2009. The main aim of these monitoring observations is to study spectral…
The present work is devoted to the study of faint Be stars observed by CoRoT in the fourth long run (LRA02). The astrophysical parameters were determined from the spectra observed with the VLT/FLAMES instruments at ESO. Spectra were fitted…
The Be stars display variable optical emission lines originating in the circumstellar disc. Here we analyse high resolution spectroscopic observations of Be stars and the distance between the peaks of H-alpha, H-beta, and H-gamma emission…
Sun-like stars are a new probe of variations in the fine-structure constant, $\alpha$, via the solar twins approach: velocity separations of close pairs of absorption lines are compared between stars with very similar stellar parameters,…
We present a spectroscopic study of 150 Classical Be stars in 39 open clusters using medium resolution spectra in the wavelength range 3800 - 9000 \AA. One-third of the sample (48 stars in 18 clusters) has been studied for the first time.…
We present the performances of a radial velocity measurement method that we developed for A-F type stars. These perfomances are evaluated through an extensive set of simulations, together with actual radial velocity observations of such…
We recently discovered a large number of highly active Be stars in the open cluster NGC 3766, making it an excellent location to study the formation mechanism of Be star disks. To explore whether similar disk appearances and/or…
A method is developed for fitting theoretically predicted astronomical spectra to an observed spectrum. Using a hierarchical Bayesian principle, the method takes both systematic and statistical measurement errors into account, which has not…
Within the scope of a Key Programme determining fundamental parameters of stars observed by HIPPARCOS, spectra of 525 B8 to F2-type stars brighter than V=8 have been collected at ESO. Fourier transforms of several line profiles in the range…