Determination of fundamental properties of giant stars by means of the Geneva photometric system

Astrophysics ◽  
1989 ◽  
Vol 31 (3) ◽  
pp. 735-742
Author(s):  
L. V. Korotina ◽  
A. V. Dragunova ◽  
N. S. Komarov
Keyword(s):  
Photometric System ◽  
Giant Stars ◽  
Fundamental Properties

New calibration of the Vilnius photometric system

2018 ◽  
Vol 14 (A30) ◽  
pp. 486-486
Author(s):  
M. Maskoliunas ◽  
J. Zdanavičius ◽  
V. Čepas ◽  
A. Kazlauskas ◽  
R. P. Boyle ◽  
...  
Keyword(s):  
Photometric Determination ◽  
High Dispersion ◽  
Physical Parameters ◽  
Photometric System ◽  
Homogeneous Sample ◽  
Giant Stars ◽  
Stellar Temperatures ◽  
Absolute Magnitudes ◽  
Gaia Dr2

AbstractThe medium-band Vilnius photometric system with the mean wavelengths at 345 (U), 374 (P), 405 (X), 466 (Y), 516 (Z), 544 (V), and 656 (S) nm for many years was an important tool to determine interstellar reddenings and distances of single stars due to its ability to classify stars of all temperatures in spectral classes and luminosity classes in the presence of different interstellar reddenings. At present, Gaia DR2 presents distances to stars with an unprecedented accuracy at least up to 3 kpc. However, multicolor photometry, which allows the classification of stars as well as the preliminary determination of stellar temperatures, gravities, metallicities and interstellar reddenings, remains an important method for distant stars. Here we present an empirical calibration of the intrinsic color indices of the Vilnius system in terms of physical parameters of stars for dwarf and giant stars of spectral classes F-G-K-M. In any attempted photometric determination of physical parameters of stars it is important to have an extensive and homogeneous sample of spectroscopically determined parameters for stars for which there are also accurate photometric data. As a source catalogue for the Vilnius photometry the latest updated version of the Catalogue of Photoelectric Observations in the Vilnius System was used, which contains compilations from the published photometry for about 11 000 stars. The stars which had both the Gaia DR2 parallaxes and the determinations of stellar parameters from high-dispersion spectra were extracted from this catalogue. The final sample contains more than 1500 stars of spectral classes F-M. The majority of these stars (ca 70%) are not reddened, for others the values of interstellar reddening AV were determined using the regular techniques of photometric classification in the Vilnius system. The absolute magnitudes MV and consequently the luminosity classes were determined using Gaia DR2 parallaxes. We present the analytical expressions for the effective temperature Teff and surface gravity logg and evaluate the errors of solutions for dwarf and giant stars. To test the accuracy of the proposed method, we have compared our results with the stars observed by Gaia and with the stellar parameters available from the large spectroscopic surveys: APOGEE, Gaia-ESO, GALAH, LAMOST, RAVE and SEGUE. The results of comparison contain 5-6 % outliers.The proposed method allows the fast and straightforward evaluation of stellar physical parameters for the stars observed in the Vilnius photometric system. Despite the fact, that the accuracy of determination is significantly lower than in the case of spectroscopic methods, the method described may be useful for distant faint stars, which are still inaccessible for spectroscopic observations.

scholarly journals Long Baseline Interferometry and Binary Stars

1983 ◽  
Vol 62 ◽  
pp. 191-201
Author(s):  
John Davis
Keyword(s):  
Binary Stars ◽  
Binary Systems ◽  
Current Status ◽  
Fundamental Properties ◽  
Long Baseline ◽  
Stellar Interferometer ◽  
Spectroscopic Binary ◽  
Future Plans ◽  
Intensity Interferometer

AbstractThe observations of α Vir with the Narrabri Stellar Intensity Interferometer demonstrated the potential of long baseline interferometry for the determination of fundamental properties of double-lined spectroscopic binary systems. Since the completion of the programme with the Narrabri instrument the Chatterton Astronomy Department has been conducting a study aimed at developing a stellar interferometer with limiting magnitude V ≳ +8 and maximum baseline ≳ 1 km (resolution at 500 nm ≲ 7 × 10−5 seconds of arc). The way in which a long baseline interferometer may be used in the study of binary stars is outlined, the requirements for this work are discussed, and the current status and future plans of the Chatterton Astronomy Department’s programme to develop a new long baseline interferometer are summarised.

On the Measurement of Atmospheric Extinction by Rufener’s Method

1979 ◽  
Vol 3 (5) ◽  
pp. 326-327
Author(s):  
Z. KviZ
Keyword(s):  
Adverse Effect ◽  
Photometric System ◽  
Photoelectric Photometry ◽  
Atmospheric Extinction ◽  
Air Mass

The coefficient of atmospheric extinction may change during the night and in fact it often does. This has an adverse effect on the determination of atmospheric extinction by simple Bouguer plot of magnitude against air mass. This effect was studied by Rufener (1964), who introduced for the purpose of accurate photoelectric photometry in the Geneva photometric system the method of two ‘extinction stars’. His method consists of the measurement of two stars of the same colour — one starting at high air mass 2 - 3, the M-star (for French montante = rising) and the second starting simultaneously in the meridian at low air mass, the D—star (for descending).

scholarly journals Determination of the spectroscopic stellar parameters for 257 field giant stars★

2015 ◽  
Vol 448 (3) ◽  
pp. 2749-2765 ◽  
Author(s):  
S. Alves ◽  
L. Benamati ◽  
N. C. Santos ◽  
V. Zh. Adibekyan ◽  
S. G. Sousa ◽  
...  
Keyword(s):  
Giant Stars

scholarly journals Determination of the fundamental properties of an M31 globular cluster from main-sequence photometry

2012 ◽  
Vol 8 (S289) ◽  
pp. 398-401
Author(s):  
Jun Ma
Keyword(s):  
Globular Cluster ◽  
Main Sequence ◽  
Distance Modulus ◽  
Population Synthesis ◽  
Fundamental Properties ◽  
Stellar Population Synthesis ◽  
Metal Abundance ◽  
Multicolor Photometry ◽  
Good Agreement

AbstractWe determined the age of the M31 globular cluster B379 using isochrones of the Padova stellar evolutionary models. At the same time, the cluster's metal abundance, its distance modulus, and reddening value were also obtained. The results obtained in this paper are consistent with previous determinations, including the age. Brown et al. constrained the age of B379 by comparing its color–magnitude diagram with isochrones of the 2006 VandenBerg models. Therefore, this paper confirms the consistency of the age scale of B379 between the Padova isochrones and the 2006 VandenBerg isochrones. The results of B379 obtained in this paper are: metallicity [M/H] = log(Z/Z⊙) = −0.325 dex, age τ = 11.0 ± 1.5 Gyr, reddening E(B − V) = 0.08 mag, and distance modulus (m − M)0 = 24.44 ± 0.10 mag. Using the metallicity, the reddening value and the distance modulus obtained in this paper, we constrained the age of B379 by comparing its multicolor photometry with theoretical stellar population synthesis models. The age of B379 obtained is 10.6−0.76+0.92 Gyr, which is in very good agreement with the determination from main-sequence photometry.

The determination of carbon and oxygen abundances in very metal-poor globular cluster giant stars

1992 ◽  
Vol 104 ◽  
pp. 1127 ◽  
Author(s):  
R. A. Bell ◽  
M. M. Briley ◽  
John E. Norris
Keyword(s):  
Globular Cluster ◽  
Giant Stars

scholarly journals Fundamental properties of Kepler and CoRoT targets – IV. Masses and radii from frequencies of minimum Δν and their implications

2019 ◽  
Vol 489 (2) ◽  
pp. 1753-1769 ◽  
Author(s):  
M Yıldız ◽  
Z Çelik Orhan ◽  
C Kayhan
Keyword(s):  
Rotational Velocity ◽  
Galactic Disc ◽  
Ionization Zone ◽  
Chemical Enrichment ◽  
Fundamental Properties ◽  
Diagnostic Potential ◽  
The Difference ◽  
The Masses ◽  
Oscillation Frequencies

ABSTRACT Recently, by analysing the oscillation frequencies of 90 stars, Yıldız, Çelik Orhan & Kayhan have shown that the reference frequencies (νmin0, νmin1, and νmin2) derived from glitches due to He ii ionization zone have very strong diagnostic potential for the determination of their effective temperatures. In this study, we continue to analyse the same stars and compute their mass, radius, and age from different scaling relations including relations based on νmin0, νmin1, and νmin2. For most of the stars, the masses computed using νmin0 and νmin1 are very close to each other. For 38 stars, the difference between these masses is less than 0.024 M$\odot$. The radii of these stars from νmin0 and νmin1 are even closer, with differences of less than 0.007 R$\odot$. These stars may be the most well known solar-like oscillating stars and deserve to be studied in detail. The asteroseismic expressions we derive for mass and radius show slight dependence on metallicity. We therefore develop a new method for computing initial metallicity from this surface metallicity by taking into account the effect of microscopic diffusion. The time dependence of initial metallicity shows some very interesting features that may be important for our understanding of chemical enrichment of Galactic Disc. According to our findings, every epoch of the disc has its own lowest and highest values for metallicity. It seems that rotational velocity is inversely proportional to 1/2 power of age as given by the Skumanich relation.

Exact modeling of photonic crystal fibers for determination of fundamental properties

2020 ◽  
Vol 56 ◽  
pp. 102177
Author(s):  
Dmytro Suslov ◽  
Matěj Komanec ◽  
Tomáš Němeček ◽  
Jan Bohata ◽  
Stanislav Zvánovec
Keyword(s):  
Photonic Crystal ◽  
Photonic Crystal Fibers ◽  
Fundamental Properties ◽  
Crystal Fibers

scholarly journals Asteroseismology of red giants to constrain angular momentum transport

2014 ◽  
Vol 9 (S307) ◽  
pp. 165-170
Author(s):  
P. Eggenberger
Keyword(s):  
Angular Momentum ◽  
Rotational Frequency ◽  
Momentum Transport ◽  
Red Giants ◽  
Angular Momentum Transport ◽  
Rotation Rates ◽  
Giant Stars ◽  
Red Giant ◽  
Core Rotation

AbstractAsteroseismic data obtained by theKeplerspacecraft have led to the recent detection and characterization of rotational frequency splittings of mixed modes in red-giant stars. This has opened the way to the determination of the core rotation rates for these stars, which is of prime importance to progress in our understanding of internal angular momentum transport. In this contribution, we discuss which constraints can be brought by these asteroseismic measurements on the modelling of angular momentum transport in stellar radiative zones.

scholarly journals Kharkiv study of near-Earth asteroids

2006 ◽  
Vol 2 (S236) ◽  
pp. 385-390 ◽  
Author(s):  
Yu. N. Krugly ◽  
N. M. Gaftonyuk ◽  
I. N. Belskaya ◽  
V. G. Chiorny ◽  
V. G. Shevchenko ◽  
...  
Keyword(s):  
Surface Properties ◽  
Crimean Astrophysical Observatory ◽  
Photometric System ◽  
Rotation Periods ◽  
Photometric Observations ◽  
National University ◽  
Ccd Observations ◽  
Asteroid Hazard ◽  
Near Earth Asteroids

AbstractThe regular CCD observations of near-Earth asteroids (NEAs) in the Institute of Astronomy of Kharkiv National University were initiated in 1995 within the framework of asteroid hazard problem in collaboration with the DLR, Institute of Planetary Research (Berlin). The main aim of the study is a determination of rotation periods and shapes of NEAs as well as astrometry of newly discovered objects. We also carry out the absolute photometry of NEAs in BVRI bands in order to put constraints on surface properties and to estimate their diameters. The observations are carried out with 0.7-m telescope of the Institute of Astronomy (Kharkiv) and with 1-m telescope of the Crimean Astrophysical Observatory (Simeiz) in the standard Johnson-Cousins photometric system. Some observations were made as an optical support of radar observation of NEAs. We present the results of photometric observations of 21 NEAs obtained in 2004-2006 which include asteroid rotation properties, diameters and shapes.

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