Precise Radial Velocities

International Astronomical Union Colloquium ◽

10.1017/s025292110000614x ◽

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.

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Search for Long-Period Radial Velocity Variations in Some Be Stars

Symposium - International Astronomical Union ◽

10.1017/s0074180900037736 ◽

1982 ◽

Vol 98 ◽

pp. 155-159

Author(s):

L. Pastori ◽

E. Antonello ◽

M. Fracassini ◽

L.E. Pasinetti

Keyword(s):

Radial Velocity ◽

Radial Velocities ◽

Be Stars ◽

Long Period ◽

Be Star ◽

Velocity Variations ◽

Periodogram Analysis

Some astronomers have suggested long period phenomena in the Be stars: Hubert (1971), Delplace and Hubert (1975), Feinstein (1975), Harmanec et al. (1976), Pustylnik (1976). In particular, Fracassini et al. (1977) have made a periodogram analysis of the radial velocities (RV) of the Be star o And from 1900 to 1976, to connect the shell appearance with eventual long-term RV variations. In the present study all the RV of seven Be stars, found in the literature from the beginning of the century up to now, have been assembled and analysed in the same way as o And, in order to find out long period phenomena (duplicity, variability, shell activity, etc…). A brief review on the studied stars may be found in Harmanec et al. (1980).

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Radial Velocity Variations in Cool Supergiants

International Astronomical Union Colloquium ◽

10.1017/s0252921100098900 ◽

1984 ◽

Vol 88 ◽

pp. 283-288

Author(s):

Hugh C. Harris

Keyword(s):

Radial Velocity ◽

Main Sequence ◽

Short Period ◽

Cool Stars ◽

Synchronous Rotation ◽

Red Supergiants ◽

Velocity Variations ◽

Orbital Periods ◽

Low Amplitude ◽

Good Agreement

AbstractA survey of F, G, and W supergiants has been carried out with the DAO radial velocity spectrometer, an efficient instrument for detecting low-amplitude velocity variations in cool stars. Observations of 78 stars over five seasons show generally good agreement with OORAVEL results for spectroscopie binaries. The majority of supergiants show low-amplitude variability, with amplitudes typically 1 to 2 km s−1. The width of the cross-correlation profile has been measured for 58 supergiants. It reveals 14 stars with unusually broad lines, indicative of rotation velocities of 15 to 35 km s−1. Several have short-period binary companions and may be in synchronous rotation. The other broad-lined stars are apparently single or with long orbital periods; they may be making their first transition from the main sequence to become red supergiants.

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

International Astronomical Union Colloquium ◽

10.1017/s0252921100016547 ◽

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.

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The Long-term Variation in the RV Tauri Star U Mon

International Astronomical Union Colloquium ◽

10.1017/s025292110003774x ◽

1995 ◽

Vol 155 ◽

pp. 409-410 ◽

Cited By ~ 4

Author(s):

Karen R. Pollard ◽

P. L. Cottrell

Keyword(s):

High Resolution ◽

Light Curve ◽

Radial Velocity ◽

Tauri Star ◽

Short Term ◽

Instability Strip ◽

Term Variation ◽

Velocity Variations

The RV Tauri stars are semiregular pulsating variables located in the brightest part of the Cepheid II instability strip. They have a characteristic light curve of alternating deep and shallow minima. A subset of the RV Tauri stars (the RVb subclass) exhibit long-term (500 to 2600 day) light and radial velocity variations. Although it is well established that the short-term variations are due to pulsations, the long-term behaviour is not well understood.BVRI photometry and high-resolution spectra of U Mon (the brightest member of the RVb subclass) were obtained at the Mt John University Observatory (MJUO) between 1990 Aug and 1994 May. The light and colour curves obtained clearly show the long-term variation in U Mon (Fig. 1(a) and (b)). The reddest colours occur slightly later than the long-term minimum in the light curve. The short-term light and colour variations are ‘damped’ at the long-term minimum.

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Photometric and Radial Velocity Variations of R CrB Near Maximum Light

International Astronomical Union Colloquium ◽

10.1017/s0252921100090758 ◽

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.

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Three Double Degenerate Candidates

International Astronomical Union Colloquium ◽

10.1017/s0252921100099516 ◽

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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Precise Radial Velocities of F, G, K Dwarfs

Symposium - International Astronomical Union ◽

10.1017/s007418090003480x ◽

1988 ◽

Vol 132 ◽

pp. 79-81

Author(s):

Bruce Campbell ◽

Gordon A. H. Walker

Keyword(s):

Radial Velocities ◽

Absorption Lines ◽

Spectroscopic Binaries ◽

Brown Dwarf ◽

Dwarf Stars ◽

Low Level ◽

The Past ◽

Velocity Variations

We have monitored changes in the radial velocities of 24 bright F, G and K dwarf stars (known spectroscopic binaries excluded) for the past six years at CFHT by imposing the absorption lines of HF gas in the spectra to act as wavelength fiducials. The average external error in the δ(velocities) which are based on some 16 stellar lines is 13 m/s corresponds to 0.6 micron in the spectrum or 0.04 of a diode spacing per line. Reductions are complete for 16 stars. There is no evidence for brown dwarf companions in the sample. Two previously unknown spectroscopic binaries were found, and seven stars show indications of significant, long-term, low-level velocity variations which could be interpreted as purturbations by companions of a few Jupiter masses with periods greater than 12 years except for γ Cep, which may have a period of 2.7 years, and ε Eri. Observing time has been guaranteed for at least two more years at CFHT.

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