Abundances in K Giant Stars. I. a Determination of the Abundances in the Hyades K Giants.

1964 ◽  
Vol 9 ◽  
pp. 81 ◽  
Author(s):  
H. L. Heifer ◽  
George Wallerstein
Keyword(s):  
Giant Stars ◽  
K Giants

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

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 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 Abundances of C, N and O in Planetary Nebulae

1989 ◽  
Vol 131 ◽  
pp. 218-218 ◽  
Author(s):  
A. A. Nikitin ◽  
A. F. Kholtygin ◽  
A. A. Sapar ◽  
T. H. Feklistova
Keyword(s):  
Planetary Nebulae ◽  
Abundance Ratio ◽  
Evolutionary Status ◽  
Spectral Features ◽  
Giant Stars ◽  
Red Giant Stars ◽  
Red Giant ◽  
Abundance Determination

The abundances of C, N and O in planetary nebulae must correspond to the evolutionary status of their progenitor red giant stars. The best spectral features for abundance determination of these elements are the recombination lines, which depend weakly on the variations of Te and ne. The abundance ratio of the ions A+ and H+ can be given by [1–3].

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

scholarly journals Detection of planet candidates around K giants. HD 40956, HD 111591, and HD 113996

2018 ◽  
Vol 610 ◽  
pp. A3 ◽  
Author(s):  
G. Jeong ◽  
B.-C. Lee ◽  
I. Han ◽  
M. Omiya ◽  
H. Izumiura ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Astronomy Observatory ◽  
Giant Stars ◽  
Long Period ◽  
Substellar Companions ◽  
Optical Astronomy ◽  
K Giants

Aims. The purpose of this paper is to detect and investigate the nature of long-term radial velocity (RV) variations of K-type giants and to confirm planetary companions around the stars. Methods. We have conducted two planet search programs by precise RV measurement using the 1.8 m telescope at Bohyunsan Optical Astronomy Observatory (BOAO) and the 1.88 m telescope at Okayama Astrophysical Observatory (OAO). The BOAO program searches for planets around 55 early K giants. The OAO program is looking for 190 G–K type giants. Results. In this paper, we report the detection of long-period RV variations of three K giant stars, HD 40956, HD 111591, and HD 113996. We investigated the cause of the observed RV variations and conclude the substellar companions are most likely the cause of the RV variations. The orbital analyses yield P = 578.6 ± 3.3 d, m sin i = 2.7 ± 0.6 MJ, a = 1.4 ± 0.1 AU for HD 40956; P = 1056.4 ± 14.3 d, m sin i = 4.4 ± 0.4 MJ, a = 2.5 ± 0.1 AU for HD 111591; P = 610.2 ± 3.8 d, m sin i = 6.3 ± 1.0 MJ, a = 1.6 ± 0.1 AU for HD 113996.

scholarly journals B (2). Local Structure: Work in High Latitudes

1955 ◽  
Vol 1 ◽  
pp. 31-32
Keyword(s):  
Density Distribution ◽  
Local Structure ◽  
Galactic Plane ◽  
The Sun ◽  
High Latitudes ◽  
Proper Motions ◽  
K Giants

The potential possibilities of research in Kapteyn's Selected Areas at intermediate and high latitudes, where magnitudes and proper motions are already available, could be fully exploited if a more accurate spectral and luminosity classification would become available, especially for the later type stars. The purpose of work on faint stars in these latitudes is manifold. At the highest latitudes the improved data can serve for a new determination of the density distribution and of the force perpendicular to the galactic plane as a function of the distance z to the plane, K(z). The limiting magnitude may be set here at m = 13.0 (photographic). At intermediate latitudes one would hope to find the correlation between the density at some distance above the galactic plane with the density in the plane. Here the limit should be set at 13.5 or 14.0, so that G and K giants can be reached up to distances of 2 to 3 kparsecs from the Sun.

scholarly journals The Gaia-ESO Survey: Spectroscopic-asteroseismic analysis of K2 stars in Gaia-ESO

2020 ◽  
Vol 643 ◽  
pp. A83
Author(s):  
C. C. Worley ◽  
P. Jofré ◽  
B. Rendle ◽  
A. Miglio ◽  
L. Magrini ◽  
...  
Keyword(s):  
Seismic Analysis ◽  
High Resolution Spectroscopy ◽  
Red Giants ◽  
Chemical Abundances ◽  
Giant Stars ◽  
Iterative Analysis ◽  
Special Project ◽  
Red Giant ◽  
Good Agreement

Context. The extensive stellar spectroscopic datasets that are available for studies in Galactic Archeaology thanks to, for example, the Gaia-ESO Survey, now benefit from having a significant number of targets that overlap with asteroseismology projects such as Kepler, K2, and CoRoT. Combining the measurements from spectroscopy and asteroseismology allows us to attain greater accuracy with regard to the stellar parameters needed to characterise the stellar populations of the Milky Way. Aims. The aim of this Gaia-ESO Survey special project is to produce a catalogue of self-consistent stellar parameters by combining measurements from high-resolution spectroscopy and precision asteroseismology. Methods. We carried out an iterative analysis of 90 K2@Gaia-ESO red giants. The spectroscopic values of Teff were used as input in the seismic analysis to obtain log g values. The seismic estimates of log g were then used to re-determine the spectroscopic values of Teff and [Fe/H]. Only one iteration was required to obtain parameters that are in good agreement for both methods and, thus, to obtain the final stellar parameters. A detailed analysis of outliers was carried out to ensure a robust determination of the parameters. The results were then combined with Gaia DR2 data to compare the seismic log g with a parallax-based log g and to investigate instances of variations in the velocity and possible binaries within the dataset. Results. This analysis produced a high-quality catalogue of stellar parameters for 90 red giant stars from K2@Gaia-ESO that were determined through iterations between spectroscopy and asteroseismology. We compared the seismic gravities with those based on Gaia parallaxes to find an offset which is similar to other studies that have used asteroseismology. Our catalogue also includes spectroscopic chemical abundances and radial velocities, as well as indicators for possible binary detections.

scholarly journals A new method for the asteroseismic determination of the evolutionary state of red-giant stars

2016 ◽  
Vol 466 (3) ◽  
pp. 3344-3352 ◽  
Author(s):  
Yvonne Elsworth ◽  
Saskia Hekker ◽  
Sarbani Basu ◽  
Guy R. Davies
Keyword(s):  
New Method ◽  
Giant Stars ◽  
Evolutionary State ◽  
Red Giant Stars ◽  
Red Giant

scholarly journals Precise radial velocities of giant stars

2018 ◽  
Vol 616 ◽  
pp. A33 ◽  
Author(s):  
Stephan Stock ◽  
Sabine Reffert ◽  
Andreas Quirrenbach
Keyword(s):  
Test Sample ◽  
Evolutionary Stage ◽  
Evolutionary Models ◽  
Planetary Evolution ◽  
Giant Stars ◽  
Small Test ◽  
Red Giant ◽  
Stellar Masses ◽  
Host Stars

Context. The determination of accurate stellar parameters of giant stars is essential for our understanding of such stars in general and as exoplanet host stars in particular. Precise stellar masses are vital for determining the lower mass limit of potential substellar companions with the radial velocity method, but also for dynamical modeling of multiplanetary systems and the analysis of planetary evolution. Aims. Our goal is to determine stellar parameters, including mass, radius, age, surface gravity, effective temperature and luminosity, for the sample of giants observed by the Lick planet search. Furthermore, we want to derive the probability of these stars being on the horizontal branch (HB) or red giant branch (RGB), respectively. Methods. We compare spectroscopic, photometric and astrometric observables to grids of stellar evolutionary models using Bayesian inference. Results. We provide tables of stellar parameters, probabilities for the current post-main sequence evolutionary stage, and probability density functions for 372 giants from the Lick planet search. We find that 81% of the stars in our sample are more probably on the HB. In particular, this is the case for 15 of the 16 planet host stars in the sample. We tested the reliability of our methodology by comparing our stellar parameters to literature values and find very good agreement. Furthermore, we created a small test sample of 26 giants with available asteroseismic masses and evolutionary stages and compared these to our estimates. The mean difference of the stellar masses for the 24 stars with the same evolutionary stages by both methods is only ΔM = 〈Mtrk. − MAst.〉 = 0.01 ± 0.20 M⊙. Conclusions. We do not find any evidence for large systematic differences between our results and estimates of stellar parameters based on other methods. In particular we find no significant systematic offset between stellar masses provided by asteroseismology to our Bayesian estimates based on evolutionary models.

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