scholarly journals Golay Stellar Boxes in the Strömgren Four-Color System

1979 ◽  
Vol 47 ◽  
pp. 207-209
Author(s):  
A. G. Davis Philip ◽  
D. Egret
Keyword(s):  
Computer Program ◽  
Data Center ◽  
B Stars ◽  
Color System

Hauck and Mermilliod (1978) have compiled a new catalogue of approximately 20,000 observations in the Strömgren four-color system. Using the facilities of the Stellar Data Center in Strasbourg, Egret and I have revised the computer program that dereddens the indices to take into account recent revisions made by Crawford (1978) in the routines for handling B stars. Then, following the method of Golay (1978), we have constructed stellar boxes in the four-color system.

scholarly journals The Strömgren Four-Color System and the Log Teff, Log G Diagram

1978 ◽  
Vol 80 ◽  
pp. 443-446
Author(s):  
Lawrence J. Relyea ◽  
A.G. Davis Philip
Keyword(s):  
Spectral Range ◽  
Hot Stars ◽  
Stellar Spectrum ◽  
Temperature Index ◽  
B Stars ◽  
Color System ◽  
Early Type Stars ◽  
Set Up ◽  
F Stars ◽  
The Many

Strömgren (1966) set up the four-color system of photometry as a means of studying early-type stars in the spectral range 0 through F. In this spectral range one of the important measures that can be made of a stellar spectrum is the magnitude of the Balmer jump. For stars of a given (b-y) color the discontinuity is very large for stars of high luminosity and small for low luminosity stars. For very hot stars (0 and B stars) this luminosity effect becomes too small to be used as a luminosity indicator, but because of this insensitivity to luminosity changes the magnitude of the Balmer discontinuity becomes a temperature indicator (see Philip and Newell 1974 and Davis and Shobbrook 1977). Photoelectric measures of the strength of the Hßline can be used in a similar, but reverse, manner. For the B and O stars the index is a measure of luminosity; for late A and F stars the index is a good temperature index. In the spectral range A0-A3 both the Balmer jump and the Beta index are functions of temperature and luminosity. For a bibliography of the many uses of Strömgren four-color and Hßphotometry see the paper prepared by Philip and Perry (1977).

scholarly journals A B-Star High Luminosity Indicator

1978 ◽  
Vol 80 ◽  
pp. 421
Author(s):  
I. Furenlid ◽  
W.L. Sanders
Keyword(s):  
Spectral Type ◽  
Spiral Structure ◽  
The Other ◽  
Be Stars ◽  
High Luminosity ◽  
B Stars ◽  
Dimensional Classification ◽  
Color System ◽  
Color Indices ◽  
Wide Slit

In an effort to sort out BIa supergiants among B-stars for use in delineating spiral structure, a photometric discriminate has been sought in the following way. Wide slit 16Å/mm (flux) spectra were obtained of a sample of B stars over a suitable spectral and luminosity range. These spectra were digitized on the PDS Microdensitometer. Numerical filters of various widths were then slid along the spectra and numerous color-indices were formed and tested. An index ℓO= u + v − 1.9 (ℓ) plotted against cO, where ℓ is a 200Å halfwidth passband centered near 3840 Å and the other magnitudes are on the Strömgren 4-color system, succeeds in separating the Ia supergiants up to B1. For stars of spectral type B1 and earlier, confusion sets in and the separation is uncertain (although a fair percentage of success is also had for types B1 and B0). This luminosity discriminate is now in use for a large spiral structure program in which all known Be stars (and perhaps eventually all B stars) are being surveyed for Ia supergiants. Spectra for 2-dimensional classification are obtained for the Ia candidates.

scholarly journals Basic Tools for Modeling Stellar and Planetary Atmospheres

2011 ◽  
Vol 7 (S282) ◽  
pp. 221-228 ◽  
Author(s):  
Ivan Hubeny
Keyword(s):  
Computer Program ◽  
Accretion Disks ◽  
Brown Dwarfs ◽  
Planetary Atmospheres ◽  
Stellar Atmospheres ◽  
Giant Planets ◽  
B Stars ◽  
Computing Model ◽  
Spectrum Synthesis ◽  
Computer Codes

AbstractMost popular computer codes for calculating model stellar and planetary atmospheres are briefly reviewed. A particular emphasis is devoted to our universal computer program Tlusty (model stellar atmospheres and accretion disks), CoolTlusty (a variant of Tlusty for computing model atmospheres of substellar-mass objects such as giant planets and brown dwarfs), and Synspec (an associated spectrum synthesis code). We show the highlights of actual applications of these codes which include extensive grids of fully line-blanketed non-LTE model atmospheres of O and B stars, and grids of model atmospheres of extrasolar giant planets and L and T dwarfs.

Photo-electric Hβ and uvby photometry

1966 ◽  
Vol 24 ◽  
pp. 170-180
Author(s):  
D. L. Crawford
Keyword(s):  
Narrow Band ◽  
Line Strength ◽  
Interference Filter ◽  
B Stars ◽  
Relative Line ◽  
The Mean ◽  
F Stars ◽  
Two Parameters ◽  
Filter Photometry ◽  
The Continuum

Early in the 1950's Strömgren (1, 2, 3, 4, 5) introduced medium to narrow-band interference filter photometry at the McDonald Observatory. He used six interference filters to obtain two parameters of astrophysical interest. These parameters he calledlandc, for line and continuum hydrogen absorption. The first measured empirically the absorption line strength of Hβby means of a filter of half width 35Å centered on Hβand compared to the mean of two filters situated in the continuum near Hβ. The second index measured empirically the Balmer discontinuity by means of a filter situated below the Balmer discontinuity and two above it. He showed that these two indices could accurately predict the spectral type and luminosity of both B stars and A and F stars. He later derived (6) an indexmfrom the same filters. This index was a measure of the relative line blanketing near 4100Å compared to two filters above 4500Å. These three indices confirmed earlier work by many people, including Lindblad and Becker. References to this earlier work and to the systems discussed today can be found in Strömgren's article inBasic Astronomical Data(7).

Calibration problems in hydrogen luminosities

1966 ◽  
Vol 24 ◽  
pp. 322-330
Author(s):  
A. Beer
Keyword(s):  
Galactic Structure ◽  
B Stars ◽  
Insight Into

The investigations which I should like to summarize in this paper concern recent photo-electric luminosity determinations of O and B stars. Their final aim has been the derivation of new stellar distances, and some insight into certain patterns of galactic structure.

A Search for β Cephei Stars in the Southern Hemisphere - Results

1979 ◽  
Vol 46 ◽  
pp. 474-503 ◽  
Author(s):  
M. Jerzykiewicz ◽  
C. Sterken
Keyword(s):  
Southern Hemisphere ◽  
B Stars ◽  
Search Program

In 1975 we started a photometric search program of examining for variability- the bright early B stars located south of -20° declination. The main purpose we had in mind was to look for hitherto undiscovered 6 Cephei variables. Therefore, we limited our program to objects spectroscopically similar to the B Cephei stars.

A general computer program for the extended plate overlap algorithm

1978 ◽  
Vol 48 ◽  
pp. 287-293 ◽  
Author(s):  
Chr. de Vegt ◽  
E. Ebner ◽  
K. von der Heide
Keyword(s):  
Computer Program ◽  
Simultaneous Determination ◽  
General Computer Program ◽  
General Computer

In contrast to the adjustment of single plates a block adjustment is a simultaneous determination of all unknowns associated with many overlapping plates (star positions and plate constants etc. ) by one large adjustment. This plate overlap technique was introduced by Eichhorn and reviewed by Googe et. al. The author now has developed a set of computer programmes which allows the adjustment of any set of contemporaneous overlapping plates. There is in principle no limit for the number of plates, the number of stars, the number of individual plate constants for each plate, and for the overlapping factor.

Structures and crystallization of vacuum-deposited amorphous Se and Sb films

1990 ◽  
Vol 48 (4) ◽  
pp. 140-141
Author(s):  
Makoto Shiojiri ◽  
Toshiyuki Isshiki ◽  
Tetsuya Fudaba ◽  
Yoshihiro Hirota
Keyword(s):  
Monte Carlo ◽  
Electron Microscope ◽  
Monte Carlo Method ◽  
Computer Program ◽  
Radial Distribution ◽  
Film Formation ◽  
Amorphous State ◽  
Two Dimensional ◽  
Amorphous Films ◽  
Binding Condition

In hexagonal Se crystal each atom is covalently bound to two others to form an endless spiral chain, and in Sb crystal each atom to three others to form an extended puckered sheet. Such chains and sheets may be regarded as one- and two- dimensional molecules, respectively. In this paper we investigate the structures in amorphous state of these elements and the crystallization.HRTEM and ED images of vacuum-deposited amorphous Se and Sb films were taken with a JEM-200CX electron microscope (Cs=1.2 mm). The structure models of amorphous films were constructed on a computer by Monte Carlo method. Generated atoms were subsequently deposited on a space of 2 nm×2 nm as they fulfiled the binding condition, to form a film 5 nm thick (Fig. 1a-1c). An improvement on a previous computer program has been made as to realize the actual film formation. Radial distribution fuction (RDF) curves, ED intensities and HRTEM images for the constructed structure models were calculated, and compared with the observed ones.

Sign in / Sign up

Export Citation Format

Share Document