scholarly journals Galactic Research With Schmidt-Telescopes

1984 ◽  
Vol 78 ◽  
pp. 247-256
Author(s):  
Wilhelm Becker
Keyword(s):  
Density Gradient ◽  
Main Sequence ◽  
Galactic Centre ◽  
Density Gradients ◽  
Main Sequence Stars ◽  
Space Density ◽  
Observational Material ◽  
General Synthesis

The use of Schmidt Telescopes for the determination of space density gradients is discussed. Space densities can be determined by a three colour photometry for main sequence stars with M< 8. 0 and later type giants of population I and for metal poor stars in higher galactic latitudes with M< 7. 0. A general synthesis of the present available results is not yet possible. But the determination of a density gradient for later type giants along a galactic radius, the distribution of metal poor stars in a galactic meridian and around the galactic centre seems to be possible with the existing observational material.

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 The light elements in a helio- and asteroseismic perspective

2009 ◽  
Vol 5 (S268) ◽  
pp. 387-394
Author(s):  
Sylvie Vauclair
Keyword(s):  
Main Sequence ◽  
Light Element ◽  
Heavy Elements ◽  
Light Elements ◽  
Main Sequence Stars ◽  
General Introduction ◽  
Helium Content ◽  
Element Abundances ◽  
The Past

AbstractAsteroseismology is a powerful tool to derive stellar parameters, including the helium content and internal helium gradients, and the macroscopic motions which can lead to lithium, beryllium, and boron abundance variations. Precise determinations of these parameters need deep analyses for each individual stars. After a general introduction on helio and asteroseismology, I first discuss the solar case, the results which have been obtained in the past two decades, and the crisis induced by the new determination of the abundances of heavy elements. Then I discuss asteroseismology in relation with light element abundances, especially for the case of main sequence stars.

scholarly journals The Arches cluster revisited

2019 ◽  
Vol 623 ◽  
pp. A84 ◽  
Author(s):  
J. S. Clark ◽  
M. E. Lohr ◽  
L. R. Patrick ◽  
F. Najarro
Keyword(s):  
Main Sequence ◽  
Mass Function ◽  
Initial Mass Function ◽  
Galactic Centre ◽  
Complete Dataset ◽  
Subsequent Determination ◽  
The Galaxy ◽  
First Time ◽  
Massive Clusters

The Arches is one of the youngest, densest and most massive clusters in the Galaxy. As such it provides a unique insight into the lifecycle of the most massive stars known and the formation and survival of such stellar aggregates in the extreme conditions of the Galactic Centre. In a previous study we presented an initial stellar census for the Arches and in this work we expand upon this, providing new and revised classifications for ∼30% of the 105 spectroscopically identified cluster members as well as distinguishing potential massive runaways. The results of this survey emphasise the homogeneity and co-evality of the Arches and confirm the absence of H-free Wolf-Rayets of WC sub-type and predicted luminosities. The increased depth of our complete dataset also provides significantly better constraints on the main sequence population; with the identification of O9.5 V stars for the first time we now spectroscopically sample stars with initial masses ranging from ∼16 M⊙ to ≥120 M⊙. Indeed, following from our expanded stellar census we might expect ≳50 stars within the Arches to have been born with masses ≳60 M⊙, while all 105 spectroscopically confirmed cluster members are massive enough to leave relativistic remnants upon their demise. Moreover the well defined observational properties of the main sequence cohort will be critical to the construction of an extinction law appropriate for the Galactic Centre and consequently the quantitative analysis of the Arches population and subsequent determination of the cluster initial mass function.

scholarly journals Empirical Determination of the Gravity-Darkening Exponent for the Secondary Components Filling the Roche Lobe in Semi-Detached Close Binary Systems

1988 ◽  
Vol 108 ◽  
pp. 217-218
Author(s):  
Masatoshi Kitamura ◽  
Yasuhisa Nakamura
Keyword(s):  
Binary Systems ◽  
Main Sequence ◽  
Close Binary System ◽  
Roche Lobe ◽  
Close Binary ◽  
Close Binaries ◽  
Main Sequence Stars ◽  
Local Gravity ◽  
Subsurface Layers

The ordinary semi-detached close binary system consists of a main-sequence primary and subgiant (or giant) secondary component where the latter fills the Roche lobe. From a quantitative analysis of the observed ellipticity effect, Kitamura and Nakamura (1986) have deduced empirical values of the exponent of gravity-darkening for distorted main-sequence stars in detached systems and found that the empirical values of the exponent for these stars with early-type spectra are close to the unity, indicating that the subsurface layers of early-main sequence stars in close binaries are actually in radiative equilibrium. The exponent of gravity-darkening can be defined by H ∝ gα with H as the bolonetric surface brightness and g as the local gravity on the stellar surface.

scholarly journals PHOTOMETRIC DETERMINATION OF THE MASS ACCRETION RATES OF PRE-MAIN-SEQUENCE STARS. II. NGC 346 IN THE SMALL MAGELLANIC CLOUD

2011 ◽  
Vol 740 (1) ◽  
pp. 11 ◽  
Author(s):  
Guido De Marchi ◽  
Nino Panagia ◽  
Martino Romaniello ◽  
Elena Sabbi ◽  
Marco Sirianni ◽  
...  
Keyword(s):  
Main Sequence ◽  
Photometric Determination ◽  
Magellanic Cloud ◽  
Small Magellanic Cloud ◽  
Main Sequence Stars ◽  
Accretion Rates

scholarly journals Determination of kinematic distances of pre-main-sequence stars in star-forming regions

2009 ◽  
Vol 5 (S266) ◽  
pp. 395-398
Author(s):  
Phillip A. B. Galli ◽  
Ramachrisna Teixeira ◽  
Christine Ducourant ◽  
Claude Bertout
Keyword(s):  
Main Sequence ◽  
Young Stars ◽  
Formation Mechanisms ◽  
Main Sequence Stars ◽  
Star Forming ◽  
Know How ◽  
Star Forming Regions ◽  
Moving Groups ◽  
Kinematic Properties

AbstractMany studies of star-forming regions have been carried out since the discovery of compact Hii regions in the late 1960s. The kinematic properties of young stars in the nearest regions with ongoing and recent star formation provide essential tests of their formation mechanisms. The detection of coeval moving groups allows determination of individual distances through the convergent-point method. As a result, the main physical properties of these stars and their early evolutionary stages can be determined if we know how distant they are.

scholarly journals Hypervelocity Stars. III. The Space Density and Ejection History of Main‐Sequence Stars from the Galactic Center

2007 ◽  
Vol 671 (2) ◽  
pp. 1708-1716 ◽  
Author(s):  
Warren R. Brown ◽  
Margaret J. Geller ◽  
Scott J. Kenyon ◽  
Michael J. Kurtz ◽  
Benjamin C. Bromley
Keyword(s):  
Main Sequence ◽  
Galactic Center ◽  
Main Sequence Stars ◽  
Space Density ◽  
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