scholarly journals Problems with the Baade Wesselink Method

1989 ◽  
Vol 111 ◽  
pp. 250-250
Author(s):  
E. Böhm-Vitense ◽  
P. Garnavich ◽  
M. Lawler ◽  
J. Mena-Werth ◽  
S. Morgan ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Radial Velocities ◽  
Phase Relations ◽  
Expansion Velocity ◽  
Effective Temperatures ◽  
The Difference

AbstractIt is well known that the Baade-Wesselink method leads to different radii for Cepheids depending on which colors are used to determine the effective temperatures. We try to find the reasons for this discrepancy. We employ yet another version of this method using only maximum and minimum radii, thereby circumventing uncertainties in the phase relations between radial velocities and colors. This has essentially no influence on the derived radii. One major uncertainty is the relation between the photospheric expansion velocity and the measured radial velocity. The main reason for the discrepant results obtained by using different colors appears to be an inconsistency in the difference in the applied temperature-color calibrations. Small changes in the d(log Teff)/d(color) can cause major changes in the derived radii.

scholarly journals Fabry-Pérot Radial Velocities of S274: a Planetary Nebula

1983 ◽  
Vol 103 ◽  
pp. 547-547
Author(s):  
E. Recillas-Cruz ◽  
P. Pismis
Keyword(s):  
Velocity Field ◽  
Radial Velocity ◽  
Planetary Nebula ◽  
Outer Boundary ◽  
Radial Velocities ◽  
Physical Parameters ◽  
Expansion Velocity ◽  
Double Points ◽  
Fabry Perot ◽  
The Mean

The bright nebula S274 (YM29), 8′ across has been classified as a planetary by Abell (1966) although it has been considered a SNR by other authors. We have determined radial velocities at 173 points on this nebula from four Fabry-Pérot interferograms. The velocity field exhibits a great deal of structure. The average expansion velocity is + 31.5 ± 8 km s−1. The mean radial velocity of S274 is not well determined due to the nature of the velocity field, while the overall velocity (173 points) is + 33 ± 21 km s−1. Points at the outer boundary yield an average of 22 ± 14 km s−1 while the average of the double points is 25 km s−1. The age of expansion of the nebula is estimated at 6.8 × 103yr. The physical parameters of this object are consistent with those of a planetary nebula.

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.

The CORAVEL Radial Velocity Data Base

2017 ◽  
Vol 13 (S334) ◽  
pp. 271-272
Author(s):  
Stéphane Udry ◽  
Maxime Marmier ◽  
Michel Mayor ◽  
Johannes Andersen ◽  
Birgitta Nordström
Keyword(s):  
Radial Velocity ◽  
Data Base ◽  
Radial Velocities ◽  
Velocity Data ◽  
Radial Velocity Data

AbstractFrom 1977 to 1999, thousands of accurate radial velocities in both hemispheres were made on a large variety of programmes with the two CORAVEL scanners. The data base of ~350000 individual observations will now be made available to complement the Gaia data.

scholarly journals Local Stellar Kinematics from RAVE data—VII. Metallicity Gradients from Red Clump Stars

2016 ◽  
Vol 33 ◽  
Author(s):  
Ö. Önal Taş ◽  
S. Bilir ◽  
G. M. Seabroke ◽  
S. Karaali ◽  
S. Ak ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Milky Way ◽  
Absolute Magnitude ◽  
Selection Effects ◽  
Stellar Kinematics ◽  
Experiment Data ◽  
Radial Gradient ◽  
Data Release ◽  
The Difference ◽  
Red Clump

AbstractWe investigate the Milky Way Galaxy’s radial and vertical metallicity gradients using a sample of 47 406 red clump stars from the RAdial Velocity Experiment Data Release 4. Distances are calculated by adopting Ks-band absolute magnitude as −1.54±0.04 mag for the sample. The metallicity gradients are calculated with their current orbital positions (Rgc and Z) and with their orbital properties (Rm and zmax): d[Fe/H]/dRgc = −0.047±0.003 dex kpc−1 for |Z| ≤ 0.5 kpc and d[Fe/H]/dRm = −0.025±0.002 dex kpc−1 for zmax ≤ 0.5 kpc. This reaffirms the radial metallicity gradient in the thin disc but highlights that gradients are sensitive to the selection effects caused by the difference between Rgc and Rm. The radial gradient is flat in the distance interval 0.5-1 kpc from the plane and then becomes positive greater than 1 kpc from the plane. The radial metallicity gradients are also eccentricity dependent. We showed that d[Fe/H]/dRm = −0.089±0.010, −0.073±0.007, −0.053±0.004 and −0.044±0.002 dex kpc−1 for ep ≤ 0.05, ep ≤ 0.07, ep ≤ 0.10 and ep ≤ 0.20 sub-samples, respectively, in the distance interval zmax ≤ 0.5 kpc. Similar trend is found for vertical metallicity gradients. Both the radial and vertical metallicity gradients are found to become shallower as the eccentricity of the sample increases. These findings can be used to constrain different formation scenarios of the thick and thin discs.

scholarly journals The Velocity Field of S308. The Ring Nebula Around the WN5 Star HD 50896

1982 ◽  
Vol 99 ◽  
pp. 305-309
Author(s):  
Paris Pişmiş ◽  
Alfonso Quintero
Keyword(s):  
Velocity Field ◽  
Radial Velocities ◽  
Expansion Velocity ◽  
Ring Nebula ◽  
Fabry Perot

Radial velocities are determined by Fabry-Pérot interferometry at 131 points of the ring nebula S308. The velocities have yielded a kinematic distance of 1.5 kpc for the object, and an expansion velocity of 45–60 km s−1. The ring nebula has a diameter of 13 pc and the age is estimated to be about 1.5 to 2×105 years.

scholarly journals Recent studies of the spectrum of V1016 Cygni

1982 ◽  
Vol 70 ◽  
pp. 161-164
Author(s):  
G. Muratorio ◽  
M. Friedjung
Keyword(s):  
Radial Velocity ◽  
Ionization Potential ◽  
Radial Velocities ◽  
Emission Lines ◽  
Computer Programme ◽  
Half Maximum ◽  
The Mean ◽  
Effective Ionization

Two coudé spectra of V1016 Cyg taken on June 24 and 27, 1979 were reduced, using a computer programme developed in Marseille. Radial velocities and full widths at half maximum were measured for the emission lines, and are summarized in the following table were VR is the mean radial velocity in km s-1, DV the velocity corresponding to the mean FWHM and Xi the effective ionization potential for the ion.

scholarly journals The Radial Velocity Projection Factor in the Pulsating Helium Star V652 Her

2000 ◽  
Vol 176 ◽  
pp. 441-442
Author(s):  
P. Montañés Rodriguez ◽  
C. S. Jeffery ◽  
R. Aznar Cuadrado ◽  
D. Pollacco
Keyword(s):  
Radial Velocity ◽  
Expansion Velocity ◽  
Complete Spectrum ◽  
Helium Star ◽  
Velocity Projection

AbstractThe behavior of the velocity projection factor was studied for three individual Lines, He ɪ 4438 Å, Si ɪɪɪ 4553 Å, and N ɪɪ 4442 Å, and for the complete spectrum in the radially pulsating helium rich star V652 Her. It is shown that the projection factor is itself a function of expansion velocity.

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 The empirical period-radius relation for pulsating stars: a synthesis based on photometric and radial velocity measurements

1986 ◽  
Vol 118 ◽  
pp. 273-274
Author(s):  
G. Burki
Keyword(s):  
Radial Velocity ◽  
Stellar Evolution ◽  
Variable Stars ◽  
Radial Velocities ◽  
Velocity Measurements ◽  
Pulsating Stars ◽  
Powerful Test ◽  
The Mean

The relation existing between the radius and the period for the pulsating stars of a given class constitutes a powerful test for the theory of stellar evolution and for the identification of the pulsation modes. In recent years, several authors have determined the mean radius of a lot of pulsating stars of various classes by applying the Baade-Wesselink method. Fig. 1 presents the resulting general logP - logR diagram grouping these determinations. The sources for the radii are given by Burki and Meylan (1986). The variable stars in known binaries have been excluded since the presence of a companion biases the radius calculation (Burki, 1984). The determinations marked by arrows are based on the radial velocities by CORAVEL (1m telescope at the Haute-Provence Observatory, France) or/and on the photometry in the Geneva system (40cm and 70cm telescopes at La Silla Observatory, Chile).

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.

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