A5087004383- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Astrophysical Phenomena and Observations
- Adaptive optics and wavefront sensing
- Astronomical Observations and Instrumentation
- Advanced Frequency and Time Standards
- Gamma-ray bursts and supernovae
- Tribology and Lubrication Engineering
- High-pressure geophysics and materials
- Space Exploration and Technology
- Rare-earth and actinide compounds
- Geophysics and Gravity Measurements
- Spectroscopy and Laser Applications
- Pulsars and Gravitational Waves Research
- Solar and Space Plasma Dynamics
- Phase Equilibria and Thermodynamics
- Galaxies: Formation, Evolution, Phenomena
- Mechanics and Biomechanics Studies
- Nuclear Physics and Applications
- History and Developments in Astronomy
Mount Wilson Observatory
2018-2024
European Southern Observatory
2016-2024
Georgia State University
2020-2023
Charles University
2015-2020
Czech Academy of Sciences, Astronomical Institute
2015-2020
Masaryk University
2012
Several dozen optical echelle spectra demonstrate that HR 6819 is a hierarchical triple. A classical Be star in wide orbit with an unconstrained period around inner 40 d binary consisting of B3 III and unseen companion circular orbit. The radial-velocity semi-amplitude 61.3 km/s the its minimum (probable) mass 5.0 Msun (6.3 +- 0.7 Msun) imply object >= 4.2 (>= 0.4 Msun), is, black hole (BH). spectroscopic time series stunningly similar to observations LB-1. triple-star architecture...
Rapid rotation is a fundamental characteristic of classical Be stars and crucial property allowing for the formation their circumstellar disks. Past evolution in mass angular momentum transferring binary system offers plausible solution to how attained fast rotation. Although subdwarf remnants donors such systems should exist abundance, only few have been confirmed due tight observational constraints. An indirect method detecting otherwise hidden companions offered by effect on outer parts...
The Gl 486 system consists of a very nearby, relatively bright, weakly active M3.5 V star at just 8 pc with warm transiting rocky planet about 1.3 R_Terra and 3.0 M_Terra that is ideal for both transmission emission spectroscopy testing interior models telluric planets. To prepare future studies, we collected light curves seven new transits observed the CHEOPS space mission radial velocities obtained MAROON-X/Gemini North CARMENES/Calar Alto telescopes, together previously published...
Abstract Rapid rotation and nonradial pulsations enable Be stars to build decretion disks, where the characteristic line emission forms. A major but unconstrained fraction of owe their rapid mass angular momentum transfer in a binary. The faint, stripped companions can be helium-burning subdwarf OB-type (sdOBs), white dwarfs (WDs), or neutron stars. We present optical/near-infrared Center for High Angular Resolution Astronomy (CHARA) interferometry 37 selected spectroscopic indications...
Context. The structure of the inner parts Be star disks (20 stellar radii) is well explained by viscous decretion disk (VDD) model, which able to reproduce observable properties most objects studied so far. outer parts, on ther hand, are not observationally well-explored, as they only at radio wavelengths. A steepening spectral slope somewhere between infrared and wavelengths was reported for several stars that were previously detected in radio, but a convincing physical explanation this...
HR 6819 is the first post-mass transfer binary system composed of a classical Be star and bloated pre-subdwarf stripped directly confirmed by interferometry. While already spun up to near-critical rotation possesses self-ejected viscous Keplerian disk, found in short-lived evolutionary stage, which it retains spectral appearance B-type main-sequence while contracting into faint subdwarf OB-type star. In order understand evolution intermediate-mass interacting binaries, fundamental parameters...
Many classical Be stars acquire their very rapid rotation by mass- and angular-momentum transfer in massive binaries, marking the first phase of evolutionary chain. Later-stage products such as Be+subdwarf- Be+neutron-star binaries (Be X-ray binaries), are also well known, although search for definitive proof Be+white dwarf companions is ongoing. Short-lived intermediate-phase objects, that is, past interaction stage but with a donor star has not yet reached end its evolution or contraction,...
Classical Be stars are possible products of close binary evolution, in which the mass donor becomes a hot, stripped O or B-type subdwarf (sdO/sdB), and gainer spins up grows disk to become star. While several Be+sdO binaries have been identified, dynamical masses other fundamental parameters available only for single system, limiting confrontation with evolution models. In this work, we present direct interferometric detections sdO companions three 28 Cyg, V2119 60 all were previously found...
Two scenarios have been proposed to match the existing observational constraints of object HR 6819. The system could consist a close inner B-type giant plus black hole (BH) binary with an additional Be companion in wide orbit. Alternatively, it be composed stripped B star and Either scenario makes 6819 cornerstone as stellar BH closest Earth, or example important transitional, non-equilibrium phase for stars solid evidence its nature. We aimed distinguish between two Both models predict...
The viscous decretion disk (VDD) model is able to explain most of the currently observable properties circumstellar disks Be stars. However, more stringent tests, focusing on reproducing multitechnique observations individual targets via physical modeling, are needed study predictions VDD under specific circumstances. In case nearby, bright star $\beta$ CMi, these circumstances a very stable low-density and late-type (B8Ve) central star. aim test thoroughly, exploiting full diagnostic...
Abstract Because many classical Be stars may owe their nature to mass and angular-momentum transfer in a close binary, the present masses, temperatures, radii of components are high interest for comparison stellar evolution models. Object κ Dra is 61.5 day single-lined binary with B6 IIIe primary. With CHARA Array instruments MIRC/MIRC-X MYSTIC, we detected secondary at (approximately photospheric) flux ratios 1.49% ± 0.10% 1.63% 0.09% H K band, respectively. From large diverse optical...
Abstract The origin of the bright and hard X-ray emission flux among γ Cas subgroup B-emission line (Be) stars may be caused by gas accretion onto an orbiting white dwarf (WD) companion. Such Be+WD binaries are predicted outcome a second stage mass transfer from helium star donor to rapidly rotating gainer star. stripped become small hot dwarfs that extremely faint compared their Be companions. Here we discuss model predictions about physical orbital properties binaries, show current...
Time series of spectroscopic, speckle-interferometric, and optical long-baseline-interferometric observations confirm that $\nu$ Gem is a hierarchical triple system. It consists an inner binary composed two B-type stars outer classical Be star. Several photospheric spectral lines the components were disentangled, revealing with very different rotational broadening ($\sim$260 $\sim$140 kms$^{-1}$, respectively), while star remain undetected. From combined spectroscopic astrometric orbital...
HD 93521 is a massive, rapidly rotating star that located about 1 kpc above the Galactic disk, and evolutionary age for its estimated mass much less than time-of-flight if it was ejected from disk. Here we present re-assessment of both kinematical timescales 93521. We calculate 39 +/- 3 Myr based upon distance proper motions Gaia EDR3 summary radial velocity measurements. then determine stellar luminosity using rotational model combined with observed spectral energy distribution distance. A...
Abstract The late-type Be star β CMi is remarkably stable compared to other stars that have been studied. This has led a realistic model of the outflowing disk by Klement et al. These results showed likely truncated at finite radius from star, which suggest evidence for an unseen binary companion in orbit. Here we report on analysis Ritter Observatory spectroscopic archive search elusive companion. We detect periodic Doppler shifts wings H α line with period 170 days and amplitude 2.25 km s...
Abstract Ground-based optical long-baseline interferometry has the power to measure orbits of close binary systems at ∼10 μ as precision. This precision makes it possible detect “wobbles” in motion due gravitational pull from additional short-period companions. We started ARrangement for Micro-Arcsecond Differential Astrometry (ARMADA) survey with Michigan Infra-Red Combiner (MIRC)/MIRC-X instrument Center High Angular Resoloution Astronomy (CHARA) array purpose detecting giant planets and...
Some evolved binaries, namely post-asymptotic giant branch are surrounded by stable and massive circumbinary disks similar to protoplanetary found around young stars. Around 10% of these transition disks: they have a large inner cavity in the dust. Previous interferometric measurements modeling ruled out being formed dust sublimation suggested that is due planet traps disk produces observed depletion refractory elements on surface post-AGB star. In this study, we test alternative scenario...
ABSTRACT Classical B emission (Be) stars are fast rotating, near-main-sequence B-type stars. The rotation and the presence of circumstellar discs profoundly modify observables active Be Our goal is to infer stellar disc parameters, as well distance interstellar extinction, using currently most favoured physical models for these objects. We present BeAtlas, a grid $61\, 600$ non-local thermodynamic equilibrium radiative transfer stars, calculated with hdust code. was coupled Monte Carlo...
The CHARA Array is an optical/infrared interferometer that combines the light from six 1-meter telescopes. With baselines ranging 34 to 331 meters, provides sub-milliarcsecond resolution measure stellar diameters, image surfaces, resolve close binary companions, and study circumstellar environments. In this paper, we present recent highlights Array, focusing on implementation of adaptive optics, ongoing development next generation beam combiners, update community access program, a discussion...
A global disk oscillation implemented in the viscous decretion (VDD) model has been used to reproduce most of observed properties well known Be star $\zeta$ Tau. 48 Librae shares several similarities with Tau -- they are both early-type stars, display shell characteristics their spectra, and exhibit cyclic $V/R$ variations but some marked differences as well, such a much denser more extended disk, longer cycle, absence so-called triple-peak features. We aim photometric, polarimetric,...
We observe the brightest member of Praesepe cluster, Epsilon Cancri, to precisely measure characteristics stars in this binary system, en route a new measurement cluster's age. present spectroscopic radial velocity measurements and interferometric observations sky-projected orbit derive masses, which we find be M_1/M_sun = 2.420 +/- 0.008 M_2/M_sun 2.226 0.004. place limits on color-magnitude positions by using luminosity ratios while trying reproduce spectral energy distribution Cancri....
Achernar, the closest and brightest classical Be star, presents rotational flattening, gravity darkening, occasional emission lines due to a gaseous disk, an extended polar wind. It is also member of close binary system with early A-type dwarf companion. We aim determine orbital parameters Achernar estimate physical properties components. monitored relative position B using broad range high angular resolution instruments VLT/VLTI (VISIR, NACO, SPHERE, AMBER, PIONIER, GRAVITY, MATISSE) over...
Abstract Castor is a system of six stars in which the two brighter objects, A and B, revolve around each other every ∼450 yr are both short-period spectroscopic binaries. They attended by more distant C, also binary. Here we report interferometric observations with Center for High Angular Resolution Astronomy (CHARA) array that spatially resolve companions B first time. We complement these new radial velocity measurements spanning 30 yr, Hipparcos intermediate data, existing astrometric...