Cool Supergiants in the Solar Neighborhood

Symposium - International Astronomical Union ◽

10.1017/s0074180900045435 ◽

1991 ◽

Vol 143 ◽

pp. 341-348

Author(s):

M. Jura

Keyword(s):

Surface Density ◽

Main Sequence ◽

Milky Way ◽

Galactic Center ◽

Solar Neighborhood ◽

Main Sequence Stars ◽

Considerable Uncertainty ◽

Red Supergiants ◽

Highly Evolved

We have identified 21 mass-losing red supergiants (20 M-type, 1 G-type, L > 105 L⊙) within 2.5 kpc of the Sun. These supergiants are highly evolved descendants of main sequence stars with initial masses larger than about 20 M⊙. The surface density projected onto the plane of the Milky Way is between about 1 and 2 kpc–2. Although with considerable uncertainty, we estimate that the mass return by the M supergiants is somewhere between 1 and 3 10-5 M⊙ kpc–2 yr–1. In the hemisphere facing the galactic center there is much less mass loss from M supergiants than from W-R stars, but in the anticenter direction, the M supergiants return more mass than do the W-R stars. The duration of the M supergiant phase appears to be between 2 and 4 105 years. During this phase a star of initially at least 20 M⊙ returns perhaps 3 to 10 M⊙ into the interstellar medium.

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A test for radial mixing using local star samples

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314011296 ◽

2012 ◽

Vol 10 (H16) ◽

pp. 357-357

Author(s):

Jincheng Yu ◽

Jerry Sellwood ◽

Carlton Pryor ◽

Li Chen ◽

Jinliang Hou

Keyword(s):

Angular Momentum ◽

Main Sequence ◽

Milky Way ◽

Galactic Center ◽

Thin Disk ◽

Main Sequence Stars ◽

Radial Gradient ◽

Stellar Temperature ◽

Effective Temperatures ◽

Constant Gradient

AbstractWe use samples of local main-sequence stars to show that the radial gradient of [Fe/H] in the thin disk of the Milky Way decreases with mean effective stellar temperature. We use the angular momentum of each star about the Galactic center to eliminate the effects of epicyclic motion, which would otherwise blur the estimated gradients. We use the effective temperatures as a proxy for mean age, and conclude that the decreasing gradient is consistent with the predictions of radial mixing due to transient spiral patterns. We find some evidence that the trend of decreasing gradient with increasing mean age breaks to a constant gradient for samples of stars whose main-sequence life-times exceed the likely age of the thin disk.

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Stellar 5 min Oscillations

International Astronomical Union Colloquium ◽

10.1017/s0252921100095828 ◽

1983 ◽

Vol 66 ◽

pp. 469-486

Author(s):

Jørgen Christensen-Dalsgaard ◽

Søren Frandsen

Keyword(s):

Spectral Type ◽

Main Sequence ◽

Total Flux ◽

The Sun ◽

Major Fraction ◽

Main Sequence Stars ◽

Red Supergiants

AbstractEstimates are given for the amplitudes of stochastically excited oscillations in Main Sequence stars and cool giants; these were obtained using the equipartition between convective and pulsational energy which was originally proposed by Goldreich and Keeley. The amplitudes of both velocity and luminosity perturbation generally increase with increasing mass along the Main Sequence as long as convection transports a major fraction of the total flux, and the amplitudes also increase with the age of the model. The 1.5 Mʘ ZAMS model, of spectral type F0, has velocity amplitudes ten times larger than those found in the Sun. For very luminous red supergiants luminosity amplitudes of up to about 0ṃ.1 are predicted, in rough agreement with observations presented by Maeder.

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A comparison of the density gradients of main sequence stars obtained by two different methods in different galactic latitudes

Symposium - International Astronomical Union ◽

10.1017/s0074180900000620 ◽

1970 ◽

Vol 38 ◽

pp. 232-235

Author(s):

W. Becker ◽

R. Fenkart

Keyword(s):

Main Sequence ◽

Milky Way ◽

Absolute Magnitude ◽

Galactic Centre ◽

Density Gradients ◽

The Sun ◽

Main Sequence Stars

The Basel Observatory program of the determination of disc- and halo-density gradients for different intervals of absolute magnitude comprises in addition to Milky Way fields several directions, all pointing to Selected Areas near a plane perpendicular to the galactic equator and passing through the sun and the galactic centre. It was started with SA 51 (Becker, 1965) and continued with Sa 57, 54 and 141 (Fenkart, 1967, 1968, 1969).

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A preliminary color-magnitude diagram for late-type stars in the solar neighborhood

Symposium - International Astronomical Union ◽

10.1017/s0074180900177502 ◽

1959 ◽

Vol 10 ◽

pp. 39-40

Author(s):

O. C. Wilson

Keyword(s):

Main Sequence ◽

Star Clusters ◽

Solar Neighborhood ◽

Late Type ◽

Main Sequence Stars ◽

Individual Values ◽

Magnitude Diagram ◽

Trigonometric Parallaxes ◽

Nearby Stars ◽

The Mean

Modern photoelectric techniques yield magnitudes and colors of stars with accuracies of the order of a few thousandths and a few hundredths of a magnitude respectively. Hence for star clusters it is possible to derive highly accurate color-magnitude arrays since all of the members of a cluster may be considered to be at the same distance from the observer. It is much more difficult to do this for the nearby stars where all of the objects concerned are at different, and often poorly determined, distances. If one depends upon trigonometric parallaxes, the bulk of the reliable individual values will refer to main sequence stars, and while the mean luminosities of brighter stars are given reasonably well by this method, the scatter introduced into a color-magnitude array by using individual trigonometrically determined luminosities could obscure important features. Somewhat similar objections could be raised against the use of the usual spectroscopic parallaxes which also should be quite good for the main sequence but undoubtedly exhibit appreciable scatter for some, at least, of the brighter stars.

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Extended stellar systems in the solar neighborhood

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834950 ◽

2019 ◽

Vol 622 ◽

pp. L13 ◽

Cited By ~ 29

Author(s):

Stefan Meingast ◽

João Alves ◽

Verena Fürnkranz

Keyword(s):

Wavelet Decomposition ◽

Stellar Population ◽

Main Sequence ◽

Milky Way ◽

Velocity Dispersion ◽

Galactic Disk ◽

Mass Function ◽

Solar Neighborhood ◽

Giant Stars ◽

Stellar Streams

We report the discovery of a large, dynamically cold, coeval stellar stream that is currently traversing the immediate solar neighborhood at a distance of only 100 pc. The structure was identified in a wavelet decomposition of the 3D velocity space of all stars within 300 pc of the Sun. Its members form a highly elongated structure with a length of at least 400 pc, while its vertical extent measures only about 50 pc. Stars in the stream are not isotropically distributed but instead form two parallel lanes with individual local overdensities, that may correspond to a remnant core of a tidally disrupted cluster or OB association. Its members follow a very well-defined main sequence in the observational Hertzsprung–Russel diagram and also show a remarkably low 3D velocity dispersion of only 1.3 km s−1. These findings strongly suggest a common origin as a single coeval stellar population. An extrapolation of the present-day mass function indicates a total mass of at least 2000 M⊙, making it larger than most currently known clusters or associations in the solar neighborhood. We estimated the age of the stream to be around 1 Gyr based on a comparison with a set of isochrones and giant stars in our member selection and find a mean metallicity of [Fe/H] = −0.04. This structure may very well represent the Galactic disk counterpart to the prominent stellar streams observed in the Milky Way halo. As such, it constitutes a new valuable probe to constrain the Galaxy’s mass distribution.

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Mass-Losing Peculiar Red Giants: The Comparison Between Theory and Observations

International Astronomical Union Colloquium ◽

10.1017/s0252921100063211 ◽

1989 ◽

Vol 106 ◽

pp. 339-347

Author(s):

M. Jura

Keyword(s):

Mass Loss ◽

Loss Rate ◽

Main Sequence ◽

Mass Loss Rate ◽

Solar Neighborhood ◽

Asymptotic Giant Branch ◽

Red Giants ◽

Main Sequence Stars ◽

Dwarf Stars ◽

White Dwarf Stars

AbstractThe mass loss from evolved red giants is considered. It seems that red giants on the Asymptotic Giant Branch (AGB) are losing between 3 and 6 10-4 MΘ kpc-2 yr-1 in the solar neighborhood. If all the main sequence stars between 1 and 5 MΘ ultimately evolve into white dwarfs with masses of 0.7 MΘ the predicted mass loss rate in the solar neighborhood from these stars is 8 10-4 MΘ kpc-2 yr-1. Although there are still uncertainties, it appears that there is no strong disagreement between theory and observation. However, it could also be that we have not yet identified much of the source of the mass-loss from pre-white dwarf stars.

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HALO7D I. The Line-of-sight Velocities of Distant Main-sequence Stars in the Milky Way Halo

The Astrophysical Journal ◽

10.3847/1538-4357/ab16cb ◽

2019 ◽

Vol 876 (2) ◽

pp. 124 ◽

Cited By ~ 1

Author(s):

Emily C. Cunningham ◽

Alis J. Deason ◽

Constance M. Rockosi ◽

Puragra Guhathakurta ◽

Zachary G. Jennings ◽

...

Keyword(s):

Main Sequence ◽

Milky Way ◽

Line Of Sight ◽

Main Sequence Stars ◽

Milky Way Halo

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From birth associations to field stars: mapping the small-scale orbit distribution in the Galactic disc

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1358 ◽

2020 ◽

Vol 495 (4) ◽

pp. 4098-4112 ◽

Cited By ~ 2

Author(s):

Johanna Coronado ◽

Hans-Walter Rix ◽

Wilma H Trick ◽

Kareem El-Badry ◽

Jan Rybizki ◽

...

Keyword(s):

Main Sequence ◽

Milky Way ◽

Space Distribution ◽

Small Scale ◽

Galactic Disc ◽

Main Sequence Stars ◽

Orbital Phase ◽

Angle Space ◽

Order Of Magnitude ◽

Gaia Dr2

ABSTRACT Stars born at the same time in the same place should have formed from gas of the same element composition. But most stars subsequently disperse from their birth siblings, in orbit and orbital phase, becoming ‘field stars’. Here, we explore and provide direct observational evidence for this process in the Milky Way disc, by quantifying the probability that orbit-similarity among stars implies indistinguishable metallicity. We define the orbit similarity among stars through their distance in action-angle space, Δ(J, θ), and their abundance similarity simply by Δ[Fe/H]. Analysing a sample of main-sequence stars from Gaia DR2 and LAMOST, we find an excess of pairs with the same metallicity (Δ[Fe/H] < 0.1) that extends to remarkably large separations in Δ(J, θ) that correspond to nearly 1 kpc distances. We assess the significance of this effect through a mock sample, drawn from a smooth and phase-mixed orbit distribution. Through grouping such star pairs into associations with a friend-of-friends algorithm linked by Δ(J,θ), we find 100s of mono-abundance groups with ≥3 (to ≳20) members; these groups – some clusters, some spread across the sky – are over an order-of-magnitude more abundant than expected for a smooth phase-space distribution, suggesting that we are witnessing the ‘dissolution’ of stellar birth associations into the field.

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