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Estimating stellar atmospheric parameters, absolute magnitudes and elemental abundances from the LAMOST spectra with Kernel-based principal component analysis
Huang, Y.; Chen, B. -Q.; Wang, C. +16 more
Accurate determination of stellar atmospheric parameters and elemental abundances is crucial for Galactic archaeology via large-scale spectroscopic surveys. In this paper, we estimate stellar atmospheric parameters - effective temperature Teff, surface gravity log g and metallicity [Fe/H], absolute magnitudes MV and MKs<…
An investigation of the rotational properties of magnetic chemically peculiar stars
Paunzen, Ernst; Hümmerich, Stefan; Bernhard, Klaus +1 more
The magnetic chemically peculiar (mCP) stars of the upper main sequence exhibit strong, globally organized magnetic fields that are inclined to the rotational axis and facilitate the development of surface abundance inhomogeneities resulting in photometric and spectroscopic variability. Therefore, mCP stars are perfectly suited for a direct measur…
Kinematics of OB-associations in Gaia epoch
Dambis, A. K.; Mel'nik, A. M.
We use stellar proper motions from the Tycho-Gaia Astrometric Solution (TGAS) catalogue to study the kinematics of OB-associations. The TGAS proper motions of OB-associations generally agree well with the Hipparcos proper motions. The parameters of the Galactic rotation curve obtained with TGAS and Hipparcos proper motions agree within the errors.…
Gaia's view of the λ Boo star puzzle
Murphy, Simon J.; Paunzen, Ernst
The evolutionary status of the chemically peculiar class of λ Boo stars has been intensely debated. It is now agreed that the λ Boo phenomenon affects A stars of all ages, from star formation to the terminal age main sequence, but the cause of the chemical peculiarity is still a puzzle. We revisit the debate of their ages and temperatures in order…
Verifying reddening and extinction for Gaia DR1 TGAS main sequence stars
Gontcharov, George A.; Mosenkov, Aleksandr V.
We compare eight sources of reddening and extinction estimates for approximately 60 000 Gaia DR1 Tycho-Gaia Astrometric Solution (TGAS) main sequence stars younger than 3 Gyr with a relative error of the Gaia parallax less than 0.1. For the majority of the stars, the best 2D dust emission-based reddening maps show considerable differences between …
Ultracool dwarf benchmarks with Gaia primaries
Gromadzki, M.; Caballero, J. A.; Montes, D. +14 more
We explore the potential of Gaia for the field of benchmark ultracool/brown dwarf companions, and present the results of an initial search for metal-rich/metal-poor systems. A simulated population of resolved ultracool dwarf companions to Gaia primary stars is generated and assessed. Of the order of ∼24 000 companions should be identifiable outsid…
On the ancient field blue straggler HR 5455
Fuhrmann, Klaus; Chini, Rolf
We report the discovery of HR 5455 as an ancient field blue straggler that upon Roche lobe overflow from its evolved companion, now a white dwarf, has been rejuvenated to a MBS = 1.32 ± 0.05 M⊙ bright F6V source with a purported age of τ ≃ 1.7 Gyr. The unequivocal evidence for HR 5455 being instead a τ ≃ 12 Gyr old Population…
A three-dimensional orbit for the binary star Alpha Andromedae
Branham, Richard L., Jr.
Stars that are both spectroscopic and optical binaries present a means to determine simultaneously the masses of the components and the distance of the system independent of trigonometric parallax. Alpha Andromedae (Alpheratz) represents such a system and, moreover, the primary is the brightest of the mercury-manganese stars. An orbit, based on 42…