Rotational velocities of A-type stars

Royer, F.; Gerbaldi, M.; Faraggiana, R.; Gómez, A. E.

doi:10.1051/0004-6361:20011422

Cited by 104 publications

(89 citation statements)

References 39 publications

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“…Figure 1 shows the LSD profile of Sirius A and its Fourier transform. Our value of projected rotational velocity of Sirius appeared to be equal to 16.26 km s −1 , in good agreement with the Royer et al (2002) result obtained from 20 high-resolution spectra of this star: v sin i = 16.22 ± 0.04 km s −1 .…”

Section: Determination Of Projected Rotational Velocitiessupporting

confidence: 91%

Rotational Velocities of the Components of 23 Binaries

Glazunova

Yushchenko

Tsymbal

et al. 2008

The Astronomical Journal

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By using high dispersion spectra obtained by the 1.8 m telescope of Bohyunsan Optical Astronomy Observatory (South Korea), multiline least-square deconvolution of line profiles, and Fourier analysis techniques, we obtained the rotational velocities of the components of 23 binary systems. The rotational velocities for nine primary, eight secondary, and one tertiary components of these systems were determined for the first time. The rotational velocities for primary components of seven systems appeared to be significantly different than the corresponding synchronous values (more than twice as fast for five systems, and less than half as fast for two systems). Our velocities for AU Mon, RY Gem, and RZ Eri are significantly lower than the previously published values obtained by using one or very few lines. We show that these discrepancies can be explained by strong blending of the lines in the spectra of the primaries with strong lines of the secondaries, by influence of gaseous streams, and maybe by nonsolar chemical compositions.

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Section: Determination Of Projected Rotational Velocitiessupporting

confidence: 91%

Rotational Velocities of the Components of 23 Binaries

Glazunova

Yushchenko

Tsymbal

et al. 2008

The Astronomical Journal

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“…The sample of stars used in the present work is primarily determined by the objects studied in Royer et al (2002aRoyer et al ( ,b, 2007, hereafter Papers I, II, and III). Because we attempt to study the rotational characteristics only of A-type stars in the MS evolutionary phase, the basis of our sample is the selection of dwarf stars with luminosity class from V to IV made in Paper III.…”

Section: Rotational Velocity Datamentioning

confidence: 99%

Rotational velocities of A-type stars

Zorec

Royer

2012

A&A

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239

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Context. In previous works of this series, we have shown that late B-and early A-type stars have genuine bimodal distributions of rotational velocities and that late A-type stars lack slow rotators. The distributions of the surface angular velocity ratio Ω/Ω crit (Ω crit is the critical angular velocity) have peculiar shapes according to spectral type groups, which can be caused by evolutionary properties. Aims. We aim to review the properties of these rotational velocity distributions in some detail as a function of stellar mass and age. Methods. We have gathered v sin i for a sample of 2014 B6-to F2-type stars. We have determined the masses and ages for these objects with stellar evolution models. The (T eff , log L/L )-parameters were determined from the uvby-β photometry and the HIPPARCOS parallaxes.Results. The velocity distributions show two regimes that depend on the stellar mass. Stars less massive than 2.5 M have a unimodal equatorial velocity distribution and show a monotonical acceleration with age on the main sequence (MS). Stars more massive have a bimodal equatorial velocity distribution. Contrarily to theoretical predictions, the equatorial velocities of stars from about 1.7 M to 3.2 M undergo a strong acceleration in the first third of the MS evolutionary phase, while in the last third of the MS they evolve roughly as if there were no angular momentum redistribution in the external stellar layers. The studied stars might start in the ZAMS not necessarily as rigid rotators, but with a total angular momentum lower than the critical one of rigid rotators. The stars seem to evolve as differential rotators all the way of their MS life span and the variation of the observed rotational velocities proceeds with characteristic time scales δt ≈ 0.2 t MS , where t MS is the time spent by a star in the MS.

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“…Therefore we assume that v sin i is obtained from an independent measurement, as e.g. in Royer et al (2002); Gray (2005); Chen et al (2011). The third assumption ensures that Eq.…”

Section: Templatementioning

confidence: 99%

“…If the observed spectrum is also noiseless and different only by the radial velocity of its source, the correlation will depend only on the object-template velocity difference and on the wavelength binning, becoming a strict equality if the velocities are equal. Royer (1999) prepared his data with the logarithmic sampling Eq. (A.1), but this is not required in principle.…”

Section: Pearson Correlationmentioning

confidence: 99%

A multi-method approach to radial-velocity measurement for single-object spectra

David

Blomme

Frémat

et al. 2014

A&A

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Context. The derivation of radial velocities from large numbers of spectra that typically result from survey work, requires automation. However, except for the classical cases of slowly rotating late-type spectra, existing methods of measuring Doppler shifts require fine-tuning to avoid a loss of accuracy due to the idiosyncrasies of individual spectra. The radial velocity spectrometer (RVS) on the Gaia mission, which will start operating very soon, prompted a new attempt at creating a measurement pipeline to handle a wide variety of spectral types. Aims. The present paper describes the theoretical background on which this software is based. However, apart from the assumption that only synthetic templates are used, we do not rely on any of the characteristics of this instrument, so our results should be relevant for most telescope-detector combinations. Methods. We propose an approach based on the simultaneous use of several alternative measurement methods, each having its own merits and drawbacks, and conveying the spectral information in a different way, leading to different values for the measurement. A comparison or a combination of the various results either leads to a "best estimate" or indicates to the user that the observed spectrum is problematic and should be analysed manually. Results. We selected three methods and analysed the relationships and differences between them from a unified point of view; with each method an appropriate estimator for the individual random error is chosen. We also develop a procedure for tackling the problem of template mismatch in a systematic way. Furthermore, we propose several tests for studying and comparing the performance of the various methods as a function of the atmospheric parameters of the observed objects. Finally, we describe a procedure for obtaining a knowledge-based combination of the various Doppler-shift measurements.

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Rotational velocities of A-type stars

Cited by 104 publications

References 39 publications

Rotational Velocities of the Components of 23 Binaries

Rotational Velocities of the Components of 23 Binaries

Rotational velocities of A-type stars

A multi-method approach to radial-velocity measurement for single-object spectra

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