Desiderata in connection by the calibration of the MK-system

1966 ◽  
Vol 24 ◽  
pp. 348-349
Author(s):  
Th. Schmidt-Kaler
Keyword(s):  
Absolute Magnitude ◽  
Review Article ◽  
Stellar Systems ◽  
Astronomical Data ◽  
Intrinsic Colour

This is only an informal remark about some difficulties I am worrying about.I have tried to recalibrate the MK system in terms of intrinsic colour (B–V)0and absolute magnitudeMv. The procedures used have been described in a review article by Voigt (Mitt. Astr. Ges.1963, p. 25–35), and the results for stars of the luminosity classes Ia-O,I and II have been given also in Blaauw's article on the calibration of luminosity criteria in vol. III (Basic Astronomical Data, p. 401) ofStars and Stellar Systems.

scholarly journals The frequency of ring galaxies and the probability of their formation by collisions

1978 ◽  
Vol 79 ◽  
pp. 117-120 ◽  
Author(s):  
V. Dostal ◽  
V. Metlov
Keyword(s):  
Spiral Galaxy ◽  
Relative Velocity ◽  
Unit Volume ◽  
Spiral Galaxies ◽  
Absolute Magnitude ◽  
Stellar Systems ◽  
Clusters Of Galaxies ◽  
Central Collisions ◽  
Ring Galaxies ◽  
Minimum Separation

A survey of ring galaxies which were discovered in 1960 by B. Vorontsov-Velyaminov has been carried out using the Morphological Catalogue of Galaxies. Clusters of galaxies were also included. Such galaxies without spiral arms constitute 0.7% of all galaxies down to 15m.0, and are 100 times less frequent than spiral galaxies. This percentage is the same for clusters, but there are fields where ring galaxies are 3–5 times more frequent than the average. the probability of nearly central chance collisions of galaxies as proposed by some theories has been calculated. It was assumed that a ring galaxy is formed from the encounter of a spiral galaxy with another galaxy if its mass or luminosity is not less than 1% of that of the principal galaxy. the minimum separation of their centres was taken to be less than 2.7 kpc, but the angles between the vectors of the relative velocity and the planes of galaxies were not restricted. the lifetime of the rings once they are formed was assumed to be 109 years and the distribution of the galactic velocities was calculated according to a Maxwellian distribution. the number of galaxies of given absolute magnitude per unit volume was taken from Holmberg (Stars and Stellar Systems, 9, 123). the curvature of the trajectories was taken into account. So conditions were chosen to be most favourable for nearly central collisions.

scholarly journals Absolute Magnitudes and Intrinsic Colours of Non-Supergiant Be Stars

1982 ◽  
Vol 98 ◽  
pp. 33-36
Author(s):  
J. R. Kozok
Keyword(s):  
Absolute Magnitude ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Be Stars ◽  
Large Sample ◽  
Galactic Clusters ◽  
Absolute Magnitudes ◽  
Image Position ◽  
Intrinsic Colour

101 normal Be stars, probable members of 56 galactic clusters and OB-associations, and more than 20 extreme Be stars in the Large Magellanic Cloud were used to derive intrinsic colours of 09-B9 (III-V)e stars. Furthermore, the correlation between the intrinsic colour (U-B)0 and the absolute magnitude of non-supergiant Be stars was confirmed to be and The aim of the present investigation is to enlarge the basis for the determination of intrinsic colours and absolute magnitudes by providing a large sample from the southern sky.

Nuclear Star Clusters in Coma confirmation of an unusually high nucleation fraction

2020 ◽  
Vol 15 (S359) ◽  
pp. 195-200
Author(s):  
Emilio Zanatta ◽  
Ruben Sanchez-Janssen ◽  
Ana L. Chies-Santos
Keyword(s):  
Star Formation ◽  
Globular Clusters ◽  
Star Clusters ◽  
Absolute Magnitude ◽  
Gas Content ◽  
Stellar Systems ◽  
Coma Cluster ◽  
The Core ◽  
Deep Imaging ◽  
Wide Range

AbstractNuclear star clusters (NSCs) are stellar systems similar in size to globular clusters (GCs) but extremely dense, comparable only to some GCs and ultra-compact dwarfs. They are present in galaxies with a wide range of masses, morphologies and gas content. There are several formation scenarios proposed for the formation of such objects, such as the merger of GCs or extreme star formation caused by the inflow of gas. Recent studies show that the presence of an NSC is related to galaxy stellar mass. Moreover, it has been suggested that NSCs are more often found in high density environments. In our work, we use deep imaging of the core regions of the Coma cluster down to an absolute magnitude of –8.2 and found that in this environment the nucleation fraction is higher than in the Virgo and Fornax clusters. We find nucleated galaxies in Coma as faint as –11.2 mag.

scholarly journals The Wolf-Rayet Stars

1975 ◽  
Vol 67 ◽  
pp. 257-274
Author(s):  
Sergej V. Rublev
Keyword(s):  
Physical Properties ◽  
Absolute Magnitude ◽  
Stellar Systems ◽  
Spectral Classification ◽  
The Absolute

This review discusses the spectral classification, the absolute magnitude, the position in stellar systems, the physical properties and the evolution of WR stars.

Spectrophotometric reductions with an IBM 1620

1966 ◽  
Vol 24 ◽  
pp. 116-117
Author(s):  
P.-I. Eriksson
Keyword(s):  
Astronomical Data ◽  
Spectrophotometric Data ◽  
Electronic Computers ◽  
The University ◽  
Near Future

Nowadays more and more of the reductions of astronomical data are made with electronic computers. As we in Uppsala have an IBM 1620 at the University, we have taken it to our help with reductions of spectrophotometric data. Here I will briefly explain how we use it now and how we want to use it in the near future.

Symbiotic Stars at Optical, Infrared and Radio Wavelengths

1979 ◽  
Vol 46 ◽  
pp. 125-149 ◽  
Author(s):  
David A. Allen
Keyword(s):  
Temperature Regime ◽  
Type Star ◽  
Stellar Systems ◽  
Symbiotic Stars ◽  
Lower Excitation ◽  
Definition Of ◽  
Original Type

No paper of this nature should begin without a definition of symbiotic stars. It was Paul Merrill who, borrowing on his botanical background, coined the termsymbioticto describe apparently single stellar systems which combine the TiO absorption of M giants (temperature regime ≲ 3500 K) with He II emission (temperature regime ≳ 100,000 K). He and Milton Humason had in 1932 first drawn attention to three such stars: AX Per, CI Cyg and RW Hya. At the conclusion of the Mount Wilson Ha emission survey nearly a dozen had been identified, and Z And had become their type star. The numbers slowly grew, as much because the definition widened to include lower-excitation specimens as because new examples of the original type were found. In 1970 Wackerling listed 30; this was the last compendium of symbiotic stars published.

Electron-deficient boron-based catalysts for C–H bond functionalisation

2021 ◽  
Author(s):  
Yuanhong Ma ◽  
Shao-Jie Lou ◽  
Zhaomin Hou
Keyword(s):  
Review Article ◽  
Current Status ◽  
Comprehensive Overview

This review article provides a comprehensive overview to recognise the current status of electron-deficient boron-based catalysis in C–H functionalisations.

Sign in / Sign up

Export Citation Format

Share Document