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 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 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 Precise radial velocities of giant stars

2019 ◽  
Vol 625 ◽  
pp. A22 ◽  
Author(s):  
Katja Reichert ◽  
Sabine Reffert ◽  
Stephan Stock ◽  
Trifon Trifonov ◽  
Andreas Quirrenbach
Keyword(s):  
Radial Velocity ◽  
Statistical Power ◽  
Radial Velocities ◽  
Dynamical Stability ◽  
Published Data ◽  
Data Sets ◽  
Velocity Data ◽  
Velocity Measurements ◽  
Velocity Variations ◽  
Radial Velocity Data

Context. Radial-velocity variations of the K giant star Aldebaran (α Tau) were first reported in the early 1990s. After subsequent analyses, the radial-velocity variability with a period of ∼629 d has recently been interpreted as caused by a planet of several Jovian masses. Aims. We want to further investigate the hypothesis of an extrasolar planet around Aldebaran. Methods. We combine 165 new radial-velocity measurements from Lick Observatory with seven already published data sets comprising 373 radial-velocity measurements. We perform statistical analyses and investigate whether a Keplerian model properly fits the radial velocities. We also perform a dynamical stability analysis for a possible two-planet solution. Furthermore, the possibility of oscillatory convective modes as cause for the observed radial-velocity variability is discussed. Results. As best Keplerian fit to the combined radial-velocity data we obtain an orbit for the hypothetical planet with a smaller period (P = 607 d) and a larger eccentricity (e = 0.33 ± 0.04) than the previously proposed one. However, the residual scatter around that fit is still large, with a standard deviation of 117 ms−1. In 2006/2007, the statistical power of the ∼620 d period showed a temporary but significant decrease. Plotting the growth of power in reverse chronological order reveals that a period around 620 d is clearly present in the newest data but not in the data taken before ∼2006. Furthermore, an apparent phase shift between radial-velocity data and orbital solution is observable at certain times. A two-planet Keplerian fit matches the data considerably better than a single-planet solution, but poses severe dynamical stability issues. Conclusions. The radial-velocity data from Lick Observatory do not further support but in fact weaken the hypothesis of a substellar companion around Aldebaran. Oscillatory convective modes might be a plausible alternative explanation of the observed radial-velocity variations.

scholarly journals HR 7308: A Unique Cepheid+

1980 ◽  
Vol 58 ◽  
pp. 425-428
Author(s):  
John R. Percy ◽  
Nancy Remage Evans
Keyword(s):  
Spectral Type ◽  
Small Amplitude ◽  
Radial Velocities ◽  
Photometric Observations ◽  
Metal Abundance ◽  
Velocity Variations

AbstractWe have obtained photometric observations and radial velocities of the F6I-IIb star HR 7308. The spectral type, the period (1d.49), the relative range and phase of light, colour and velocity variations all suggest that the star is a small-amplitude Cepheid. The metal abundance appears to be normal. However, the light amplitude decreased slowly during 1978 from 0m.3 to 0m.1, and increased during 1979 and 1980 from 0m.05 to 0m.15. Such behaviour is unprecedented in a population I Cepheid.

Application of the Telluric-Line Technique to Study Late-Type Stars for Radial-Velocity Variations

1999 ◽  
Vol 170 ◽  
pp. 48-51
Author(s):  
Robert Greimel ◽  
Stephenson L.S. Yang
Keyword(s):  
Radial Velocity ◽  
Line Profile ◽  
Radial Velocities ◽  
Early Type ◽  
Late Type ◽  
Reduction Procedure ◽  
Temporal Sampling ◽  
Velocity Variations ◽  
Convenient Technique ◽  
Telluric Line

AbstractAlthough the use of telluric lines as wavelength fiducials to measure radial velocities does not achieve as high a precision as other fiducial-imposition techniques, this very convenient technique can be used concurrently with other observing programs to increase the temporal sampling of target stars. We have been carrying out a program to monitor the line-profile variations of early-type non-radial pulsators at the Hα and He I 667.8-nm region. With the rather modest reciprocal dispersion of 1nm/mm and the use of a 4096-element CCD, the telluric lines in the 630-nm region are also available in the observed spectra. We decided to use these telluric lines as wavelength fiducials to monitor bright, latetype stars for radial-velocity variations. As an experiment, we have also decided to reduce the spectra using available simple IRAF tasks to see how high a velocity precision can be achieved with only minor tweaking. The precision certainly would not rival other precise techniques, but the convenience in both the observing and reduction procedure may enable more target stars to be monitored by more observers. Moreover, interesting results can still be obtained with a mere 100 m/s precision. The result for a few late-type stars which also have prior HF velocities will be presented.

Coravel Measurements of IAU and Southern Potential Radial-Velocity Standard Stars. A Zero Point Discussion

1984 ◽  
Vol 88 ◽  
pp. 299-310
Author(s):  
M. Mayor ◽  
E. Maurice
Keyword(s):  
Radial Velocity ◽  
Observational Data ◽  
Zero Point ◽  
Variable Stars ◽  
Radial Velocities ◽  
Variable Velocity ◽  
Velocity Measurements ◽  
Similar Difference ◽  
Systematic Effects ◽  
Velocity Variations

AbstractRadial velocity measurements have been carried out since 1981 with the spectrometer CORAVEL at ESO, La Silla. Almost one thousand measurements of IAU radial velocity standard stars and of potential southern standard stars have been acquired by the different observers (mean precision per measurement 0.2 km/s).Among the measured IAU standard stars, at least four have shown clear radial-velocity variations from 1981 to 1984 (HD 36673, 156014, 44131, 115521).The comparison between CORAVEL mean velocities and IAU values reveals a difference of approximately 0.8 km/s between bright (mv <4.3) and faint IAU (mv >4.3) standards (Vr(IAUB) - Vr(IAUF) = +0.8 km/s). A similar difference also appears when comparing IAU standard velocities and those measured with the Victoria spectrometer, Fletcher et al. (1982).Thus, IAU standard stars not only include radial-velocity variable stars (intrinsic variables and SB) but they also present zero-point systematic effects.In the present paper we correct the radial velocities of the bright IAU standard stars so that they now belong to the same system as the faint ones. After elimination of variable velocity stars and stars showing large differences between IAU values and recent radial-velocity determinations, an homogeneous list of 34 IAU standard stars is obtained. These revised radial velocities are based on IAU values and new determinations obtained with the Victoria spectrometer and with CORAVEL at La Silla. These stars are distributed between the declinations δ = -82° and δ = +28°.This paper uses observational data in advance of the publication by CORAVEL observers of the 7th of the series of papers: “Radial velocities of southern stars obtained with the photoelectric scanner CORAVEL”.

scholarly journals An Extension of the Search for Spectroscopic Binaries in M3

1985 ◽  
Vol 113 ◽  
pp. 99-101
Author(s):  
Carlton P. Pryor ◽  
David W. Latham ◽  
Martha L. Hazen-Liller
Keyword(s):  
Radial Velocity ◽  
Globular Cluster ◽  
Convincing Evidence ◽  
Time Span ◽  
Radial Velocities ◽  
Spectroscopic Binaries ◽  
Spectroscopic Binary ◽  
Velocity Variations ◽  
Cluster Modelling

We have obtained 295 new radial velocities for the 112 giants in the globular cluster M3 previously observed by Gunn and Griffin. Our velocities have a typical accuracy of 0.8 km/s per measurement and have been combined with the Gunn and Griffin data in order to search for radial velocity variations over a time span of ten years. We find no convincing evidence that any of the giants observed are spectroscopic binaries with one notable exception, von Zeipel 164, which we believe is the first spectroscopic binary to be found in a globular cluster. Modelling of the velocity variations that would be expected in our data for a variety of binary populations confirms Gunn and Griffin's conclusion that binaries with separations of less than 10 AU must occur much less frequently among the giants of M3 than among the population I field stars.

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

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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