Spectral Matching for Elemental Abundances of Evolved Stars of Globular Clusters
... Sodium-oxygen anticorrelation of 47 Tuc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 Tuc spectra from SALT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sky location of the stars of the different datasets of 47 Tuc. . . . . . . ...
... Sodium-oxygen anticorrelation of 47 Tuc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 Tuc spectra from SALT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sky location of the stars of the different datasets of 47 Tuc. . . . . . . ...
The Nature of the Stars
... apart as possible—at opposite sides of the Earth’s orbit. The direction from Earth to a nearby star changes as our planet orbits the Sun, and the nearby star appears to move back and forth against the background of more distant stars (Figure 17-2). This motion is called stellar parallax. The paralla ...
... apart as possible—at opposite sides of the Earth’s orbit. The direction from Earth to a nearby star changes as our planet orbits the Sun, and the nearby star appears to move back and forth against the background of more distant stars (Figure 17-2). This motion is called stellar parallax. The paralla ...
The spectroscopic Hertzsprung
... stars that have a luminosity larger than the luminosity of a single star of comparable mass and evolutionary state. Kippenhahn & Weigert (1990) showed that main sequence stars are expected to obey the relation L ∼ M α µβ , where µ is the average mean molecular weight and β > 1. An overluminosity is ...
... stars that have a luminosity larger than the luminosity of a single star of comparable mass and evolutionary state. Kippenhahn & Weigert (1990) showed that main sequence stars are expected to obey the relation L ∼ M α µβ , where µ is the average mean molecular weight and β > 1. An overluminosity is ...
Chemical analysis of 24 dusty (pre-) main
... in abundance analyses and the fairly high projected rotational velocities severely limit the amount of suitable lines. For a few slowly rotating stars (e.g. HD 18256, HD 20010, HD 104327 and HD 139614) we were able to use hundreds of lines in the analysis; the average value for the amount of lines i ...
... in abundance analyses and the fairly high projected rotational velocities severely limit the amount of suitable lines. For a few slowly rotating stars (e.g. HD 18256, HD 20010, HD 104327 and HD 139614) we were able to use hundreds of lines in the analysis; the average value for the amount of lines i ...
Chemical composition of 90 F and G disk dwarfs
... very accurate due to different spectral types and thus different flux distributions of the components, it may be better than the value from the parallax method. Hence, for a few stars with large differences in absolute magnitudes between the photometry and parallax determination, we adopt the photom ...
... very accurate due to different spectral types and thus different flux distributions of the components, it may be better than the value from the parallax method. Hence, for a few stars with large differences in absolute magnitudes between the photometry and parallax determination, we adopt the photom ...
Angular Momentum Evolution of Young Low
... The evolution of rotational distributions from 1 Ma to the old disk population shown in Fig. 1 reveals a number of features: 1. The initial distribution of spin rates at an age of about 2 Ma is quite wide over the whole mass range from 0.2 to 1.0 M⊙, with the bulk of rotational periods ranging from ...
... The evolution of rotational distributions from 1 Ma to the old disk population shown in Fig. 1 reveals a number of features: 1. The initial distribution of spin rates at an age of about 2 Ma is quite wide over the whole mass range from 0.2 to 1.0 M⊙, with the bulk of rotational periods ranging from ...
Conference Abstract Booklet here.
... White dwarfs represent the end point of stellar evolution for the majority of stars. As such, they are excellent astrophysical laboratories. They are structurally simple, with electron degenerate cores surrounded by thin surface layers of helium and/or hydrogen. The g-mode pulsations provide a windo ...
... White dwarfs represent the end point of stellar evolution for the majority of stars. As such, they are excellent astrophysical laboratories. They are structurally simple, with electron degenerate cores surrounded by thin surface layers of helium and/or hydrogen. The g-mode pulsations provide a windo ...
The spectroscopic Hertzsprung-Russell diagram
... Methods. Our spectroscopic Hertzsprung-Russell (sHR) diagram shows the inverse of the flux-mean gravity versus the effective temperature. Observed stars whose spectra have been quantitatively analyzed can be entered in this diagram without the knowledge of the stellar distance or absolute brightness ...
... Methods. Our spectroscopic Hertzsprung-Russell (sHR) diagram shows the inverse of the flux-mean gravity versus the effective temperature. Observed stars whose spectra have been quantitatively analyzed can be entered in this diagram without the knowledge of the stellar distance or absolute brightness ...
... of a quadratic pulsation ephemerides (a secularly decreasing period) and an orbital timing model which fits the O-C data within the photometry uncertainties (Saha & White 1990; Kiss et al. 1995; Wade et al. 1999). Wade et al. (1999) also show convincing evidence that the centre-of-mass velocities fo ...
Hot subdwarf stars-galactic orbits and distribution perpendicular to
... (small) sample had disk orbits but 1 star had an orbit with z-distance maxima ranging from 8 to 20 kpc. Evidence for more stars with halo orbits was given by de Boer et al. (1995). We have investigated 41 stars for their kinematic behaviour. The choice of stars was solely determined by the availabil ...
... (small) sample had disk orbits but 1 star had an orbit with z-distance maxima ranging from 8 to 20 kpc. Evidence for more stars with halo orbits was given by de Boer et al. (1995). We have investigated 41 stars for their kinematic behaviour. The choice of stars was solely determined by the availabil ...
Distance determination for RAVE stars using stellar models
... used to illuminate a host of substructures in the Galactic halo. The strength of photometric distances is that they can be constructed for a wide range of stellar populations. An important recent study was carried out by Ivezić et al. (2008). In this work they took high-precision multi-band optical ...
... used to illuminate a host of substructures in the Galactic halo. The strength of photometric distances is that they can be constructed for a wide range of stellar populations. An important recent study was carried out by Ivezić et al. (2008). In this work they took high-precision multi-band optical ...
Have You Seen Canopus Tonight?
... diameter than the Sun. If correct, this supersized star would fill approximately 90 percent of Mercury’s orbit! (See Figure 3.) Although masses of stars like Canopus are uncertain, Canopus may contain something like ten times more material than the Sun. However, because about 400,000 Suns could fit ...
... diameter than the Sun. If correct, this supersized star would fill approximately 90 percent of Mercury’s orbit! (See Figure 3.) Although masses of stars like Canopus are uncertain, Canopus may contain something like ten times more material than the Sun. However, because about 400,000 Suns could fit ...
1998 - Universitäts-Sternwarte München
... We adopt a purely spectroscopic approach. The analysis is strictly differential with respect to the Sun. The modeling of the spectral lines is based on T. Gehren’s (1975) atmosphere program that makes use of the standard assumptions such as hydrostatic equilibrium, plane-parallel layers and local th ...
... We adopt a purely spectroscopic approach. The analysis is strictly differential with respect to the Sun. The modeling of the spectral lines is based on T. Gehren’s (1975) atmosphere program that makes use of the standard assumptions such as hydrostatic equilibrium, plane-parallel layers and local th ...
Star
A star is a luminous sphere of plasma held together by its own gravity. The nearest star to Earth is the Sun. Other stars are visible from Earth during the night, appearing as a multitude of fixed luminous points in the sky due to their immense distance from Earth. Historically, the most prominent stars were grouped into constellations and asterisms, and the brightest stars gained proper names. Extensive catalogues of stars have been assembled by astronomers, which provide standardized star designations.For at least a portion of its life, a star shines due to thermonuclear fusion of hydrogen into helium in its core, releasing energy that traverses the star's interior and then radiates into outer space. Once the hydrogen in the core of a star is nearly exhausted, almost all naturally occurring elements heavier than helium are created by stellar nucleosynthesis during the star's lifetime and, for some stars, by supernova nucleosynthesis when it explodes. Near the end of its life, a star can also contain degenerate matter. Astronomers can determine the mass, age, metallicity (chemical composition), and many other properties of a star by observing its motion through space, luminosity, and spectrum respectively. The total mass of a star is the principal determinant of its evolution and eventual fate. Other characteristics of a star, including diameter and temperature, change over its life, while the star's environment affects its rotation and movement. A plot of the temperature of many stars against their luminosities, known as a Hertzsprung–Russell diagram (H–R diagram), allows the age and evolutionary state of a star to be determined.A star's life begins with the gravitational collapse of a gaseous nebula of material composed primarily of hydrogen, along with helium and trace amounts of heavier elements. Once the stellar core is sufficiently dense, hydrogen becomes steadily converted into helium through nuclear fusion, releasing energy in the process. The remainder of the star's interior carries energy away from the core through a combination of radiative and convective processes. The star's internal pressure prevents it from collapsing further under its own gravity. Once the hydrogen fuel at the core is exhausted, a star with at least 0.4 times the mass of the Sun expands to become a red giant, in some cases fusing heavier elements at the core or in shells around the core. The star then evolves into a degenerate form, recycling a portion of its matter into the interstellar environment, where it will contribute to the formation of a new generation of stars with a higher proportion of heavy elements. Meanwhile, the core becomes a stellar remnant: a white dwarf, a neutron star, or (if it is sufficiently massive) a black hole.Binary and multi-star systems consist of two or more stars that are gravitationally bound, and generally move around each other in stable orbits. When two such stars have a relatively close orbit, their gravitational interaction can have a significant impact on their evolution. Stars can form part of a much larger gravitationally bound structure, such as a star cluster or a galaxy.