Asymmetry of metallic spectral lines in Cepheids

AbstractA program of high resolution spectroscopic observations of Cepheids has been carried out at Mt John University Observatory for several years. Radial velocities and asymmetries have been measured for selected metallic lines using the method of Wallerstein et al (1992).The line profiles show the largest asymmetry at phases of maximum inward velocity. The asymmetry at phases of maximum outward velocity is smaller and sometimes in the same direction as for the inward velocity maxima. Enhanced asymmetry is also noticed at phases where the bump appears on the radial velocity curve.To date our models are unable to predict such behaviour. It is important that a satisfactory explaination for these observations be found so that the accuracy of Baade-Wesselink radius solutions for such stars can be assessed.

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New Spectroscopic Observations of Dwarf Nova BZ Ursae Majoris with Extremely Unusual Emission Lines Profiles

International Astronomical Union Colloquium ◽

10.1017/s0252921100153138 ◽

2004 ◽

Vol 194 ◽

pp. 269-269 ◽

Cited By ~ 1

Author(s):

V. V. Neustroev ◽

S. V. Zharikov ◽

A. Medvedev ◽

A. Shearer

Keyword(s):

Radial Velocity ◽

Emission Line ◽

Velocity Curve ◽

Emission Lines ◽

Radial Velocity Curve ◽

Dwarf Nova ◽

Preliminary Results ◽

Spectroscopic Observations ◽

Medium Resolution ◽

Hα Emission

We present preliminary results of new spectroscopic observations of dwarf nova BZ UMa in quiescence. Fifty medium resolution spectra allow us to reproduce the radial velocity curve from the Hα emission line. We confirm that BZ UMa shows extremely unusual emission lines profiles, Unlike the classical single or the double-peaked profiles usually observed in spectra of dwarf novae, emission lines of BZ UMa consist of at least five peaks.

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A spectroscopic study of southern binary Cepheids

International Astronomical Union Colloquium ◽

10.1017/s0252921100011039 ◽

2004 ◽

Vol 193 ◽

pp. 403-406

Author(s):

O.K.L. Petterson ◽

Michael D. Albrow ◽

P.L. Cottrell ◽

A. Fokin

Keyword(s):

High Resolution ◽

Spectroscopic Study ◽

Variable Stars ◽

Radial Velocities ◽

Spectral Lines ◽

Hydrodynamical Models ◽

Spectroscopic Observations ◽

Line Level ◽

Good Agreement

AbstractHigh-resolution spectroscopic observations have been made of a number of southern binary Cepheids to determine their dynamical masses. The stars are part of a long-term programme to observe southern variable stars for which a valuable long-term database has been obtained. The most recent radial velocities have a precision of ~300ms−1, allowing the detection of velocity differences of ~l kms−1 with confidence. Masses were determined for three systems: the 9-day Cepheid S Mus (6.0±0.4M⊙), the double-mode Cepheid Y Car (4.5±1.8M⊙) and the 5-day Cepheid V350Sgr (6.0±0.9M⊙). For five Cepheids (YZCar, AX Cir, V636 Sco, W Sgr and T Mon) new or improved orbital solutions were found. Line level effects have been observed in several species of lines. Most Cepheids were observed to show the same progression of line level effects. Using non-linear radiative hydrodynamical models, we have compared the results of these models with our observations. These have shown that AX Cir and YZ Car have the following properties: L = 2050 L⊙, M = 4.8 M), Teff = 5900 K and L = 9350 L∩, M = 7.7M∩, Teff = 5590 K. Our models show no strong Shockwaves being produced. Good agreement was found between the observed and modelled spectral lines Fe I 5576Å, Si II 6347Å, Ba II 5853Å and Ca II 8542Å.

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Discrepant Measurements of the Radial Velocities of SS Cygni: Solution to the Problem

International Astronomical Union Colloquium ◽

10.1017/s0252921100104713 ◽

1987 ◽

Vol 93 ◽

pp. 113-118

Author(s):

E.L. Robinson

Keyword(s):

Radial Velocity ◽

Accretion Disk ◽

White Dwarf ◽

Center Of Mass ◽

Velocity Curve ◽

Radial Velocities ◽

Radial Velocity Curve ◽

Dwarf Nova

AbstractWe show that the discrepancies among the various measurements of the radial velocity curve of the K5 V star in the dwarf nova SS Cyg have been caused by (1) poor choices of lines for measuring its velocity and (2) large distortions in its velocity caused by heating from the white dwarf and its accretion disk. The correct K velocity of the center of mass of the K5 V star is 158 ± 3 km s−1.

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A Study of Ultraviolet Spectra of Delta Sagittae

Symposium - International Astronomical Union ◽

10.1017/s0074180900122272 ◽

1992 ◽

Vol 151 ◽

pp. 273-275

Author(s):

A. Akalin ◽

S. Engin

Keyword(s):

High Resolution ◽

Radial Velocity ◽

Orbital Motion ◽

Velocity Curve ◽

Velocity Variation ◽

High Resolution Spectrum ◽

Radial Velocity Curve ◽

Radial Velocity Variation ◽

Component Matching ◽

Absorption Features

High resolution spectrum of the VV Cephei type star δ Sge (M2 II + A0 V) observed with the IUE satellite between 1979–1985 have been analysed. The radial velocity curves of non blended absorption features have been formed. Observed radial velocities are compared with the theoretical radial velocity curve due to orbital motion. We found that observed radial velocity variation is the resultant of radial velocity of hotter component and wind velocity around this star. The wind is perturbed by hotter component. Matching the UV continuum fluxes obtained from IUE high resolution spectra to fluxes of Kurucz model atmospheres yields Te=11000±500 °K. Thus the spectral type of hot component was found as A0.

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Dependence of the absorption-line profiles and radial-velocity curve of the optical star in an X-ray binary on the orbital inclination and component-mass ratio

Astronomy Reports ◽

10.1134/1.2085250 ◽

2005 ◽

Vol 49 (10) ◽

pp. 801-813 ◽

Cited By ~ 7

Author(s):

M. K. Abubekerov ◽

É. A. Antokhina ◽

A. M. Cherepashchuk

Keyword(s):

Radial Velocity ◽

Absorption Line ◽

Velocity Curve ◽

Line Profiles ◽

Mass Ratio ◽

Radial Velocity Curve ◽

Orbital Inclination ◽

X Ray ◽

Optical Star

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Astrometric Radial Velocities From Hipparcos

Highlights of Astronomy ◽

10.1017/s153929960002219x ◽

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.

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Wolf-Rayet binaries: old friends and new acquaintances

Symposium - International Astronomical Union ◽

10.1017/s0074180900204890 ◽

1999 ◽

Vol 193 ◽

pp. 26-37 ◽

Cited By ~ 2

Author(s):

Virpi S. Niemela ◽

Roberto Gamen ◽

Nidia I. Morrell ◽

Sixto Giménez Benítez

Keyword(s):

Radial Velocity ◽

Binary Systems ◽

Magellanic Cloud ◽

Elliptic Orbit ◽

Spectral Lines ◽

Small Magellanic Cloud ◽

Orbital Elements ◽

Spectroscopic Observations ◽

Short Period ◽

Old Friends

Observations of WR stars in binary systems are discussed, emphasizing constraints on our knowledge of the binary frequency of WR stars, and of WR stars as a distinctive class of objects. Radial velocity orbits of newly discovered binaries, e.g., WR 29, a short period WN7+OB binary in our Galaxy, and SMC/AB 7, a massive WN+O7 binary in the Small Magellanic Cloud, are presented. New spectroscopic observations of binary systems with previously known orbits are also reported, showing in the case of WR 21 evidence of change of the orbital elements as derived from different spectral lines. An elliptic orbit for CV Ser is also illustrated.

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The Radial Velocity Curve of V652 Her (BD+13°3224)

International Astronomical Union Colloquium ◽

10.1017/s0252921100090679 ◽

1985 ◽

Vol 87 ◽

pp. 109-115

Author(s):

P.W. Hill ◽

C.S. Jeffery

Keyword(s):

Radial Velocity ◽

Time Resolution ◽

High Frequency ◽

Velocity Curve ◽

Velocity Data ◽

Effective Surface ◽

Radial Velocity Curve ◽

Minimum Radius ◽

Helium Star ◽

Radial Velocity Data

AbstractNew radial velocity data for the pulsating extreme helium star V652 Her (BD+13°3224) have been obtained with a time resolution of 100 s. High frequency structure in the radial velocity curve is detected, and a comparison with previous data suggests that the detailed shape of the velocity curve is variable. The data imply that the effective surface gravity must increase by a factor of 4 at minimum radius.

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