scholarly journals A determination of the space density and birth rate of hydrogen-line (DA) white dwarfs in the Galactic plane, based on the UVEX survey

2013 ◽  
Vol 434 (4) ◽  
pp. 2727-2741 ◽  
Author(s):  
Kars Verbeek ◽  
Paul J. Groot ◽  
Gijs Nelemans ◽  
Simone Scaringi ◽  
Ralf Napiwotzki ◽  
...  
Keyword(s):  
White Dwarfs ◽  
Birth Rate ◽  
Galactic Plane ◽  
Hydrogen Line ◽  
Space Density

The Space Density of Hot White Dwarfs

1983 ◽  
Vol 5 (2) ◽  
pp. 230-232
Author(s):  
Neill Reid ◽  
D.T. Wickramasinghe ◽  
M.S. Bessell
Keyword(s):  
Star Formation ◽  
Observational Studies ◽  
White Dwarfs ◽  
Luminosity Function ◽  
Birth Rate ◽  
Main Sequence ◽  
Mass Density ◽  
Statistical Significance ◽  
Space Density ◽  
History Of

The space density of degenerate stars is an important parameter in Galactic Structure studies, not only because white dwarfs represent a significant fraction of the local mass density, but also because they act as tracers of the history of star formation (see e.g., Bessell 1978). Combining the present day luminosity function with theoretical cooling tracks allows constraints to be set on the birth rate of main sequence progenitors. However, since white dwarfs are intrinsically low luminosity objects, observational studies are hampered by difficulties in defining complete samples large enough to have statistical significance. This paper discusses preliminary results from one method of tackling this problem.

scholarly journals Periastron Observations of the PSR B1259-63/SS 2883 Binary System

1996 ◽  
Vol 165 ◽  
pp. 263-269
Author(s):  
Simon Johnston
Keyword(s):  
Galactic Plane ◽  
Radio Spectrum ◽  
Wide Frequency Range ◽  
Optical Observations ◽  
Rotation Measure ◽  
Linearly Polarized ◽  
Be Star ◽  
Frequency Survey ◽  
The Magnetic Field

PSR B1259-63 is a 47-millisecond pulsar which was discovered in a high frequency survey of the galactic plane (Johnston et al. 1992a) and was subsequently found to be in a highly eccentric orbit with a main-sequence Be star known as SS 2883 (Johnston et al. 1992b). Radio observations of the pulsar led to a phase connected timing solution which predicted the epoch of periastron to be 1994 January 9 (MJD 49361.2); optical observations of the Be star led to a determination of its mass and of the size of its circumstellar disk (Johnston et al. 1994a): the star is of approximate spectral type B1e, with mass 10 M⊙ and radius 6 R⊙. If this mass is correct and the pulsar has a mass of 1.4 M⊙, then the inclination angle of the plane of the orbit with respect to the sky is 35°. This pulsar has an unusually flat radio spectrum compared to most pulsars, which makes it easily detectable up to 8.4 GHz. The narrow pulse permits dispersion and scattering measurements for studying the ionized plasma in the system. Moreover, the pulses are highly linearly polarized and permit determination of the rotation measure (RM), allowing measurements of the magnetic field along the line of sight. The 3.5-yr orbit of the pulsar around its companion thus provides us with an excellent probe of the stellar wind of the Be star over a wide frequency range.

Spectroscopic Determination of Mass for a Sample of DAO White Dwarfs

White Dwarfs ◽  
2003 ◽  
pp. 143-146
Author(s):  
S. A. Good ◽  
M. A. Barstow ◽  
M. R. Burleigh ◽  
J. B. Holberg ◽  
D. Sing ◽  
...  
Keyword(s):  
White Dwarfs ◽  
Spectroscopic Determination

scholarly journals The Surface Density of Quasars

1978 ◽  
Vol 79 ◽  
pp. 295-303 ◽  
Author(s):  
J.G. Bolton ◽  
Ann Savage
Keyword(s):  
Surface Density ◽  
Luminosity Function ◽  
Statistical Significance ◽  
Comprehensive Investigation ◽  
Space Density ◽  
Close Pairs

A knowledge of the surface density of quasars as a function of magnitude is important for two reasons. Firstly it is necessary in order to assess the possible statistical significance of close pairs of quasars or the association between quasars and bright galaxies. Secondly it is a necessary step in the determination of the space density or luminosity function of QSOs. We have carried out what we believe to be currently the most comprehensive investigation into the surface density of quasars. Three techniques have been used in this investigation. These are

scholarly journals Marseille Observatory Hα Survey of the Southern Galactic Plane and Magellanic Clouds

1998 ◽  
Vol 15 (1) ◽  
pp. 9-13 ◽  
Author(s):  
D. Russeil ◽  
Y. M. Georgelin ◽  
P. Amram ◽  
Y. P. Georgelin ◽  
A. Laval ◽  
...  
Keyword(s):  
Spiral Structure ◽  
Galactic Plane ◽  
Hii Regions ◽  
Magellanic Clouds ◽  
Spectral Information ◽  
Fourth Quadrant ◽  
Diffuse Emission ◽  
Gas Kinematics ◽  
Fabry Perot

AbstractThe ionised gas regions, which are the main tracers of the spiral arms, can be used for the study and determination of the spiral structure of our Galaxy. Towards this goal, the Marseille Observatory elaborated and developed an instrument, using a scanning Fabry–Perot interferometer, particularly suited for the observation of extended objects. A survey of the southern Galactic plane then started at the beginning of 1990. The major instrumental aim is to obtain spectral information, and therefore the ionised gas kinematics, in each pixel of the observed fields. Already 300 fields of 38′×38′ have been observed in Hα with a spatial resolution of 9″×9″, covering almost the entire fourth quadrant of the Galactic plane, and numerous discrete HII regions have been detected, as well as diffuse emission which is widely distributed. Also, the Magellanic Clouds have been studied using the same instrument.

scholarly journals Three Double Degenerate Candidates

1989 ◽  
Vol 114 ◽  
pp. 163-166
Author(s):  
Diana Foss
Keyword(s):  
Radial Velocity ◽  
Lower Limit ◽  
White Dwarfs ◽  
Radial Velocities ◽  
Close Binary ◽  
Space Density ◽  
Velocity Variations

This poster reports the results of a search for variable radial velocities in 29 DA white dwarfs. The survey was sensitive to periods between 1h and 66d, although non-ideal sampling limited the longest practically detectable period to 2d. Three stars were discovered to have radial velocity shifts at above the 3σ level. The discovery of these stars, along with that of Saffer, et al. (1988) can put only a lower limit on the space density of close binary white dwarfs, as this survey was less than 100% efficient in detecting radial velocity variations, and its efficiency depended strongly on period.

scholarly journals 18. Model Atmospheres for Hydrogen-Deficient White Dwarfs

1971 ◽  
Vol 42 ◽  
pp. 125-129
Author(s):  
I. Bues
Keyword(s):  
Effective Temperature ◽  
White Dwarfs ◽  
Atmospheric Parameters ◽  
Metal Abundances ◽  
Different Parts

The determination of atmospheric parameters for non-DA white dwarfs is investigated with the computed helium-rich model atmospheres by Bues (1970). Only poor predictions are possible from UBV colors alone for DB and DC stars. From uvby colors a determination of effective temperature is possible within 1000 K. Profiles of lines in different parts of the spectrum are necessary for better results.A deficiency of metal abundances for the cooler non-DA stars is obtained.

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