Velocity Variations in Beta Centauri

1968 ◽  
Vol 1 (3) ◽  
pp. 82-83 ◽  
Author(s):  
R.R. Shobbrook ◽  
J.W. Robertson
Keyword(s):  
Double Star ◽  
Radial Velocities ◽  
Spectral Lines ◽  
Single Star ◽  
Spectroscopic Evidence ◽  
Stellar Interferometer ◽  
Velocity Variations

This programme was undertaken because the preliminary observations of Beta Centauri with the Narrabri stellar interferometer (Hanbury Brown, Davis, Allen, and Rome) show that the correlation received is not consistent with that expected from a single star. The Lick Catalogue of Radial Velocities states that β Cen is a Bl II star. The Narrabri results are consistent with several models; in particular, it may be a double star with components of similar brightness, or it may have a very luminous, extended atmosphere or shell surrounding it. The latter possibility is perhaps unlikely on the spectroscopic evidence, as there are neither emission nor sharp absorption components in the spectral lines.

scholarly journals Astrometric Radial Velocities From Hipparcos

1998 ◽  
Vol 11 (1) ◽  
pp. 564-564
Author(s):  
D. Dravins ◽  
L. Lindegren ◽  
S. Madsen ◽  
J. Holmberg
Keyword(s):  
Radial Velocity ◽  
High Precision ◽  
Radial Velocities ◽  
Radial Motion ◽  
Spectral Lines ◽  
Parallel Program ◽  
Stellar Surface ◽  
Space Astrometry ◽  
Stellar Motion ◽  
Surface Convection

Abstract Space astrometry now permits accurate determinations of stellar radial motion, without using spectroscopy. Although the feasibility of deducing astrometric radial velocities from geometric projection effects was realized already by Schlesinger (1917), only with Hipparcos has it become practical. Such a program has now been carried out for the moving clusters of Ursa Major, Hyades, and Coma Berenices. Realized inaccuracies reach about 300 m/s (Dravins et al. 1997). Discrepancies between astrometric and spectroscopic radial velocities reveal effects (other than stellar motion) that affect wavelength positions of spectral lines. Such are caused by stellar surface convection, and by gravitational redshifts. A parallel program (Gullberg & Dravins 1997) is analyzing high-precision spectroscopic radial velocities for different spectral lines in these stars, using the ELODIE radial-velocity instrument atHaute-Provence.

scholarly journals A Plan for a New Generation 2 m-Class Telescope in Indonesia

1984 ◽  
Vol 80 ◽  
pp. 409-410
Author(s):  
Karel A. Van Der Hucht
Keyword(s):  
Double Star ◽  
Radial Velocities ◽  
Spectroscopic Binaries ◽  
Theoretical Research ◽  
60Th Anniversary ◽  
Additional Tool ◽  
New Generation

AbstractOne of the prime astrophysical interests of the Observatorium Bosscha is, and has always been, double star research: visual double star research with the double-60 cm Zeiss telescope (dedicated in 1928), and theoretical research of evolved massive spectroscopic binaries (since 1972). For one thing, this is the very reason that this IAU Colloquium No. 80, celebrating the 60th anniversary of the Observatorium Bosscha in Lembang, is devoted to binary astrophysics.Up to now, visual, photographic, and photometric tools have been used for binary research at the Observatorium Bosscha. An important, essential additional tool for binary research is spectrographic equipment, in order to measure radial velocities of binary components.

scholarly journals SUSI’s Potential for Double Star Research

1992 ◽  
Vol 135 ◽  
pp. 521-526
Author(s):  
John Davis
Keyword(s):  
Angular Resolution ◽  
Double Star ◽  
Double Stars ◽  
Stellar Interferometer ◽  
New Instrument

AbstractThe Sydney University Stellar Interferometer (SUSI) is currently undergoing commissioning and will soon commence its astronomical program in which observations of double stars will form a major component. With its 640-m long North–South array of input siderostats, the new instrument will have unprecedented angular resolution.

Radial Velocities for the Pulsating Subdwarf B Star PG 1605+072

2002 ◽  
Vol 185 ◽  
pp. 376-377
Author(s):  
V.M. Woolf ◽  
C.S. Jeffery ◽  
D.L. Pollacco
Keyword(s):  
Radial Velocity ◽  
Line Shape ◽  
High Speed ◽  
Radial Velocities ◽  
Peak Amplitude ◽  
Amplitude Ratios ◽  
Time Line ◽  
Photometric Observations ◽  
Velocity Variations ◽  
Over Time

AbstractWe have performed high-speed spectroscopy of the pulsating subdwarf B star PG 1605+072. Its radial velocity variations have frequencies similar to those reported from photometric observations. Peak amplitude ratios are different, probably as a result of power shifting between modes over time. Line-shape variations have also been detected.

scholarly journals Precise Radial Velocities

1992 ◽  
Vol 135 ◽  
pp. 67-72
Author(s):  
Gordon A.H. Walker
Keyword(s):  
Radial Velocity ◽  
Radial Velocities ◽  
Velocity Variations ◽  
Low Amplitude

AbstractCurrent techniques for the detection of long-term, low-amplitude (<50 m s−1), radial velocity variations are briefly reviewed together with some of their most successful programs. In the era of 8- to 10-m telescopes we must strive for a precision of < 1ms−1.

scholarly journals A Two-Dimensional White-Light Amplitude Interferometer

1979 ◽  
Vol 50 ◽  
pp. 31-1-31-13
Author(s):  
James B. Breckinridge
Keyword(s):  
White Light ◽  
Double Star ◽  
Two Dimensional ◽  
Stellar Interferometer ◽  
Speckle Patterns ◽  
New Material

AbstractA review of the applications of a point-symmetric, 180-degree, rotational shearing interferometer is given. Material includes, photographs of the Michelson stellar interferometer fringes from α Lyr, measures of amplitude of phase excursions in the atmosphere, and a measure of the order of interference in speckle patterns. New material includes unpublished double star speckle patterns to illustrate the isoplanatic patch, a measure of the time fluctuations of the earths' atmosphere, and measurements of the properties of a 256 channel linear reticon.

scholarly journals Photometric and Radial Velocity Variations of R CrB Near Maximum Light

1985 ◽  
Vol 87 ◽  
pp. 191-197
Author(s):  
A.V. Raveendran ◽  
B.N. Ashoka ◽  
N. Kameswara Rao
Keyword(s):  
Fourier Analysis ◽  
Radial Velocity ◽  
Radial Velocities ◽  
Light Curves ◽  
Circumstellar Dust ◽  
Maximum Light ◽  
V Band ◽  
L Band ◽  
Velocity Variations ◽  
Visual Light

Abstract:Fourier analysis of the light curves of RCrB in V band near maximum shows that in addition to several significant short periods there is a modulation of the visual light with a period around 1170 day, similar to that of L band flux, noticed by strecker. This indicates that there is some contribution to the visual light variations of the star from the pulsating circumstellar dust. Radial velocities of R CrB obtained at Kavalur during February-May 1985 show variations with a period around 47 days.

scholarly journals Formation Depths of Spectral Lines in Cepheids

1995 ◽  
Vol 155 ◽  
pp. 373-374
Author(s):  
Michael D. Albrow ◽  
P. L. Cottrell
Keyword(s):  
Spectral Line ◽  
Velocity Fields ◽  
Radial Velocities ◽  
Spectral Lines ◽  
Line Formation ◽  
Ionisation Potential ◽  
Velocity Gradients ◽  
Different Levels ◽  
Line Depth

There has been a number of observational programmes that have endeavoured to investigate the atmospheric velocity fields in Cepheids (e.g., Sanford 1956, Wallerstein et al. 1992, Butler 1993). These studies measured the radial velocities of lines of different strength, excitation and ionisation potential as these provide an indication of line formation at different levels in the atmosphere. From these measurements, the presence of velocity gradients can be inferred, but determination of the magnitude of such gradients requires knowledge of the spectral line depth of formation. Through dynamical modelling we are endeavouring to ascertain what is actually being measured in the above observational programmes.

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.

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