scholarly journals A test for radial mixing using local star samples

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.

scholarly journals Stellar Temperature Scale and Bolometric Corrections

1973 ◽  
Vol 54 ◽  
pp. 231-271 ◽  
Author(s):  
J. R. W. Heintze
Keyword(s):  
Temperature Scale ◽  
Main Sequence ◽  
Main Sequence Stars ◽  
Correction Formula ◽  
Stellar Temperature ◽  
Effective Temperatures ◽  
Future Work ◽  
Intrinsic Colour

In chapter 1 basic methods are reviewed, and applications and suggestions for future work are presented. In chapter 2 a revision is given of the intrinsic-colour relation in the U, B, V system of hot main-sequence stars. Some temperature-colour relations are discussed in chapter 3, where also a correction formula is given for the effects of interstellar reddening on the effective temperatures of hot main-sequence stars. An empirical mass-luminosity relation is given in chapter 4.

scholarly journals Cool Supergiants in the Solar Neighborhood

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.

Chemo-dynamical signatures in simulated Milky Way-like galaxies

2017 ◽  
Vol 12 (S330) ◽  
pp. 263-264
Author(s):  
Alessandro Spagna ◽  
Anna Curir ◽  
Marco Giammaria ◽  
Mario G. Lattanzi ◽  
Giuseppe Murante ◽  
...  
Keyword(s):  
Milky Way ◽  
Galactic Plane ◽  
Dynamical Evolution ◽  
Thin Disk ◽  
Disk Galaxy ◽  
Radial Gradient ◽  
Heating Mechanism ◽  
Disk Evolution ◽  
Inside Out

AbstractWe have investigated the chemo-dynamical evolution of a Milky Way-like disk galaxy, AqC4, produced by a cosmological simulation integrating a sub-resolution ISM model. We evidence a global inside-out and upside-down disk evolution, that is consistent with a scenario where the “thin disk” stars are formed from the accreted gas close to the galactic plane, while the older “thick disk” stars are originated in situ at higher heights. Also, the bar appears the most effective heating mechanism in the inner disk. Finally, no significant metallicity-rotation correlation has been observed, in spite of the presence of a negative [Fe/H] radial gradient.

Angular momentum transport in pre-main-sequence stars of intermediate mass

Solar Physics ◽  
1990 ◽  
Vol 128 (1) ◽  
pp. 287-298 ◽  
Author(s):  
C. Vigneron ◽  
A. Mangeney ◽  
C. Catala ◽  
E. Schatzman
Keyword(s):  
Angular Momentum ◽  
Main Sequence ◽  
Momentum Transport ◽  
Main Sequence Stars ◽  
Intermediate Mass ◽  
Angular Momentum Transport

scholarly journals Angular-Momemtum Transfer by Nonradial Oscillations in Massive Main-Sequence Stars

1993 ◽  
Vol 137 ◽  
pp. 287-289
Author(s):  
Umin Lee ◽  
Hideyuki Saio
Keyword(s):  
Angular Momentum ◽  
Reynolds Stress ◽  
Main Sequence ◽  
Rotation Velocity ◽  
Main Sequence Stars ◽  
Oscillation Analysis ◽  
Oscillation Velocity ◽  
Time Average ◽  
Linear Oscillation ◽  
Nonradial Oscillations

Angular mementum distribution is one of the most important factors for stellar structutre and evolution. Among other mechanisms, angular momentum is transfered by non-axisymmetric oscillations (nonradial oscillations). In this mechanism the angular momentum is carried mainly by the Reynolds stress, which is proportional to the product between radial and azimuthal components of oscillation velocity; i.e., (Φ direction is the direction of rotation velocity). In the linear oscillation analysis, the phase difference between and is with A finite value of δ, which arises from excitation or damping of the oscillation, makes the time average of finite. Positive angular momentum is transfered from the driving zone to the damping zone by a prograde mode (Osaki 1986).

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

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).

scholarly journals Outflow from Protostars and Angular Momentum Transfer

2001 ◽  
Vol 200 ◽  
pp. 401-405
Author(s):  
Kohji Tomisaka
Keyword(s):  
Angular Momentum ◽  
Momentum Transfer ◽  
Main Sequence ◽  
Magnetic Torque ◽  
Main Sequence Stars ◽  
The Core ◽  
Mhd Simulations ◽  
Self Similar Solution ◽  
Self Similar ◽  
Almost All

Dynamical contraction of a slowly-rotating magnetized cloud is studied using 2D magnetohydrodynamical (MHD) simulations. In the isothermal stage (n ≲ nA ∼ 1010cm−3), the cloud evolves similarly to that expected from the Larson-Penston self-similar solution and experiences a run-away collapse. However, after the central density exceeds ∼ nA, an accretion disk is formed around an adiabatic core. Just outside the core, an outflow is ejected by the effect of magnetic torque (magneto-centrifugal wind). Since ∼ 10% of the mass is ejected with almost all the angular momentum, the specific angular momentum of the protostellar core reduces to that observed in pre-main-sequence stars.

scholarly journals Evolution of an Accretion Disk in the Symbiotic Binary CI Cyg

1996 ◽  
Vol 158 ◽  
pp. 335-338
Author(s):  
Joanna Mikołajewska
Keyword(s):  
Boundary Layer ◽  
Accretion Disk ◽  
Main Sequence ◽  
Activity Cycle ◽  
Thin Disk ◽  
Photometric Data ◽  
Disk Accretion ◽  
Main Sequence Stars ◽  
Full Activity ◽  
Classical Boundary

AbstractWe have combined IUE spectra with optical spectroscopic and photometric data collected over a few orbits of the symbiotic binary CI Cyg to follow the evolution of a disk and boundary layer during a full activity cycle. Our results indicate an extended optically thin disk during quiescent periods, which evolves into an optically thick state in an eruption; a classical boundary layer at the inner edge of the disk ionizes a surrounding H II region in quiescence, and this emission fades during the rise to visual maximum in outburst. This evolution of Ṁ rivals that observed in classical CVs and pre-main sequence stars, so symbiotic systems like CI Cyg represent another opportunity to study the physics of disk accretion.

scholarly journals The Scatter of Metallicities of Stars in the Solar Neighbourhood

1996 ◽  
Vol 169 ◽  
pp. 431-432 ◽  
Author(s):  
B. Fuchs ◽  
C. Dettbarn ◽  
R. Wielen
Keyword(s):  
Main Sequence ◽  
Thin Disk ◽  
Thick Disk ◽  
Solar Neighbourhood ◽  
Data Sets ◽  
Main Sequence Stars ◽  
The Third ◽  
Nearby Stars ◽  
Velocity Dispersions

It is well known that the velocity dispersions of the stars in the solar neighbourhood increase with their ages (Wielen 1977). In Fig.1 we show |W| weighted velocity dispersions (cf. Wielen 1977) of the stars in the Third Catalog of Nearby Stars (Gliese and Jahreiß 1994). Open symbols indicate main sequence stars and crosses indicate McCormick stars, a kinematically unbiased subset of the CNS3, respectively, whereas the filled symbols are the Edvardsson et al. (1993) data. Stars older than 14 Gyr are not shown because they are probably thick disk stars (Freeman 1991). We have assumed a maximum age of the old thin disk stars of 12 Gyr as suggested by the Edvardsson et al. data. As can be seen from Fig.1 both data sets fit ideally together. The solid line indicates a σ ∝ τ1/2 law.

scholarly journals The rotational evolution of young low mass stars

2007 ◽  
Vol 3 (S243) ◽  
pp. 231-240 ◽  
Author(s):  
Jérôme Bouvier
Keyword(s):  
Angular Momentum ◽  
Accretion Disk ◽  
Main Sequence ◽  
Young Stars ◽  
Sequence Evolution ◽  
Main Sequence Stars ◽  
Low Mass Stars ◽  
Rotational Evolution ◽  
Low Mass

AbstractStar-disk interaction is thought to drive the angular momentum evolution of young stars. In this review, I present the latest results obtained on the rotational properties of low mass and very low mass pre-main sequence stars. I discuss the evidence for extremely efficient angular momentum removal over the first few Myr of pre-main sequence evolution and describe recent results that support an accretion-driven braking mechanism. Angular momentum evolution models are presented and their implication for accretion disk lifetimes discussed.

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