A combined
Fourier-Bessel transformation method 
to derive accurate rotational velocities

Piters, A. J. M.; Groot, P.J.; Paradijs, J.A. van

doi:10.1051/aas:1996219

Cited by 4 publications

(15 citation statements)

References 4 publications

(7 reference statements)

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“…We note that the FT zero position is even less sensitive to nonrotational broadening than the Bessel-Fourier transform proposed by Piters, Groot, & van Paradijs (1996). In fact, according to Fig.…”

Section: Influence Of Nonrotational Broadening Effectsmentioning

confidence: 66%

Accurate stellar rotational velocities using the Fourier transform of the cross correlation maximum

Díaz

González

Levato

et al. 2011

A&A

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Aims. We propose a method for measuring the projected rotational velocity v sin i with high precision even in spectra with blended lines. Though not automatic, our method is designed to be applied systematically to large numbers of objects without excessive computational requirement. Methods. We calculated the cross correlation function (CCF) of the object spectrum against a zero-rotation template and used the Fourier transform (FT) of the CCF central maximum to measure the parameter v sin i taking the limb darkening effect and its wavelength dependence into account. The procedure also improves the definition of the CCF base line, resulting in errors related to the continuum position under 1% even for v sin i = 280 km s −1 . Tests with high-resolution spectra of F-type stars indicate that an accuracy well below 1% can be attained even for spectra where most lines are blended. Results. We have applied the method to measuring v sin i in 251 A-type stars. For stars with v sin i over 30 km s −1 (2-3 times our spectra resolution), our measurement errors are below 2.5% with a typical value of 1%. We compare our results with Royer et al. (2002a) using 155 stars in common, finding systematic differences of about 5% for rapidly rotating stars.

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Section: Influence Of Nonrotational Broadening Effectsmentioning

confidence: 66%

Accurate stellar rotational velocities using the Fourier transform of the cross correlation maximum

Díaz

González

Levato

et al. 2011

A&A

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“…Rather than considering a pure Fourier transform, Piters et al (1996) used the Fourier-Bessel transform (FBT) of the line profile. The idea behind this is that the Fourier transform of a pure rotational profile, which has an ellipsoidal shape in the absence of limb darkening, is proportional to a first-order Bessel function and that the Bessel transform of this Fourier transform has a maximum at v sin i.…”

Section: The Fourier-bessel Methodsmentioning

confidence: 99%

“…The idea behind this is that the Fourier transform of a pure rotational profile, which has an ellipsoidal shape in the absence of limb darkening, is proportional to a first-order Bessel function and that the Bessel transform of this Fourier transform has a maximum at v sin i. The method by Piters et al (1996) is implemented with the aim of indicating this maximum by the user, from a graphical user interface. The code has the option of being applied to a large number of spectra, as was done and illustrated in Groot et al (1996) for a sample of F-type stars.…”

Section: The Fourier-bessel Methodsmentioning

confidence: 99%

On the use of the Fourier transform to determine the projected rotational velocity of line-profile variable B stars

Aerts

Simón‐Díaz

Groot

et al. 2014

A&A

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Context. The Fourier transform method is a popular tool for deriving the rotational velocities of stars from their spectral line profiles. However, its domain of validity does not include line-profile variables with time-dependent profiles. Aims. We investigate the performance of the method for such cases, by interpreting the line-profile variations of spotted B stars and of pulsating B stars, as if their spectral lines were caused by uniform surface rotation along with macroturbulence. Methods. We perform time-series analysis and harmonic least-squares fitting of various line diagnostics and of the outcome of several implementations of the Fourier transform method. Results. We find that the projected rotational velocities derived from the Fourier transform vary appreciably during the pulsation cycle whenever the pulsational and rotational velocity fields have similar magnitudes. The macroturbulent velocities derived while ignoring the pulsations can vary by tens of km s −1 during the pulsation cycle. The temporal behaviour of the deduced rotational and macroturbulent velocities are in antiphase with each other. The rotational velocity is in phase with the second moment of the line profiles. Conclusions. The application of the Fourier method to stars with considerable pulsational line broadening may lead to an appreciable spread in the values of the rotation velocity, and, by implication, of the deduced value of the macroturbulence. These two quantities should therefore not be derived from single snapshot spectra if the aim is to use them as a solid diagnostic evaluating stellar evolution models of slow-to-moderate rotators.

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“…This method was first described by Gray (1973) and reviewed in Gray (1978). It is discussed in detail more recently by Piters et al (1996). Weak metallic lines are the best diagnostic to derive v sin i, since they are (by definition) free of saturation effects and least affected by collisional broadening.…”

Section: Sin I From Metallic Linesmentioning

confidence: 99%

Statistical properties of a sample of periodically variable B-type supergiants

Lefever¹,

Puls

Aerts

2006

A&A

144

245

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Aims. We have studied a sample of 28 periodically variable B-type supergiants selected from the HIPPARCOS mission and 12 comparison stars covering the whole B-type spectral range. Our goal is to test if their variability is compatible with opacity-driven non-radial oscillations. Methods. We have used the NLTE atmosphere code FASTWIND to derive the atmospheric and wind parameters of the complete sample through line profile fitting. We applied the method to selected H, He, and Si line profiles, measured with the high resolution CES spectrograph attached to the ESO CAT telescope in La Silla, Chile. Results. From the location of the stars in the (log T eff , log g) diagram, we suggest that variability of our sample supergiants is indeed due to the gravity modes resulting from the opacity mechanism. We find nine of the comparison stars to be periodically variable as well, and suggest them to be new α Cyg variables. We find marginal evidence of a correlation between the amplitude of the photometric variability and the wind density. We investigate the wind momentum-luminosity relation for the whole range of B spectral type supergiants, and find that the later types (>B5) perfectly follow the relation for A supergiants. Additionally, we provide a new spectral type -T eff calibration for B supergiants. Conclusions. Our results imply the possibility of probing internal structure models of massive stars of spectral type B through seismic tuning of gravity modes.

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A combined Fourier-Bessel transformation method to derive accurate rotational velocities

Cited by 4 publications

References 4 publications

Accurate stellar rotational velocities using the Fourier transform of the cross correlation maximum

Accurate stellar rotational velocities using the Fourier transform of the cross correlation maximum

On the use of the Fourier transform to determine the projected rotational velocity of line-profile variable B stars

Statistical properties of a sample of periodically variable B-type supergiants

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