A new version of the moment method, optimized for mode identification in
multiperiodic stars

Briquet, Maryline; Aerts, C.

doi:10.1051/0004-6361:20021683

Cited by 84 publications

(126 citation statements)

References 13 publications

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“…Depending on the degree and azimuthal order m, modes leave characteristic patterns in the spectroscopic data, which can be used for mode identification if we are able to decipher them. In order to achieve this, we use the pixel-bypixel method to detect the pulsation frequencies from the variation in the line profiles and use the Fourier-parameter fit (FPF) method (Zima 2006) to identify the modes, as well as the line profiles' moments (Briquet & Aerts 2003). We have investigated our spectroscopic data using both methods, but the broad lines imply the pixel-by-pixel method to be best suited.…”

Section: Study Of Line Profile Variationsmentioning

confidence: 99%

Gravito-inertial and pressure modes detected in the B3 IV CoRoT target HD 43317

Pápics

Briquet

Baglin

et al. 2012

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Context. OB stars are important building blocks of the Universe, but we have only a limited sample of them well understood enough from an asteroseismological point of view to provide feedback on the current evolutionary models. Our study adds one special case to this sample, with more observational constraints than for most of these stars. Aims. Our goal is to analyse and interpret the pulsational behaviour of the B3 IV star HD 43317 using the CoRoT light curve along with the ground-based spectroscopy gathered by the HARPS instrument. This way we continue our efforts to map the β Cep and SPB instability strips. Methods. We used different techniques to reveal the abundances and fundamental stellar parameters from the newly-obtained highresolution spectra. We used various time-series analysis tools to explore the nature of variations present in the light curve. We calculated the moments and used the pixel-by-pixel method to look for line profile variations in the high-resolution spectra. Results. We find that HD 43317 is a single fast rotator (v rot ≈ 50% v crit ) and hybrid SPB/β Cep-type pulsator with Solar metal abundances. We interpret the variations in photometry and spectroscopy as a result of rotational modulation connected to surface inhomogeneities, combined with the presence of both g and p mode pulsations. We detect a series of ten consecutive frequencies with an almost constant period spacing of 6339 s as well as a second shorter sequence consisting of seven frequencies with a spacing of 6380 s. The dominant frequencies fall in the regime of gravito-inertial modes.

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Section: Study Of Line Profile Variationsmentioning

confidence: 99%

Gravito-inertial and pressure modes detected in the B3 IV CoRoT target HD 43317

Pápics

Briquet

Baglin

et al. 2012

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115

146

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“…In both cases, we make use of the famias software package (Zima 2008) for the extraction of the individual frequencies and for the mode identification. The analysis is based on the moment (Aerts et al 1992;Briquet & Aerts 2003) and pixel-by-pixel (Zima 2008) methods.…”

Section: Asteroseismic Targets: the Cases Of 20 Cvn And Hd 189631mentioning

confidence: 99%

Denoising spectroscopic data by means of the improved least-squares deconvolution method

Tkachenko

Reeth

Tsymbal

et al. 2013

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Context. The MOST, CoRoT, and Kepler space missions have led to the discovery of a large number of intriguing, and in some cases unique, objects among which are pulsating stars, stars hosting exoplanets, binaries, etc. Although the space missions have delivered photometric data of unprecedented quality, these data are lacking any spectral information and we are still in need of ground-based spectroscopic and/or multicolour photometric follow-up observations for a solid interpretation. Aims. The faintness of most of the observed stars and the required high signal-to-noise ratio (S/N) of spectroscopic data both imply the need to use large telescopes, access to which is limited. In this paper, we look for an alternative, and aim for the development of a technique that allows the denoising of the originally low S/N (typically, below 80) spectroscopic data, making observations of faint targets with small telescopes possible and effective. Methods. We present a generalization of the original least-squares deconvolution (LSD) method by implementing a multicomponent average profile and a line strengths correction algorithm. We tested the method on simulated and real spectra of single and binary stars, among which are two intrinsically variable objects. Results. The method was successfully tested on the high-resolution spectra of Vega and a Kepler star, KIC 04749989. Application to the two pulsating stars, 20 Cvn and HD 189631, showed that the technique is also applicable to intrinsically variable stars: the results of frequency analysis and mode identification from the LSD model spectra for both objects are in good agreement with the findings from literature. Depending on the S/N of the original data and spectral characteristics of a star, the gain in S/N in the LSD model spectrum typically ranges from 5 to 15 times. Conclusions. The technique introduced in this paper allows an effective denoising of the originally low S/N spectroscopic data. The high S/N spectra obtained this way can be used to determine fundamental parameters and chemical composition of the stars. The restored LSD model spectra contain all the information on line profile variations present in the original spectra of pulsating stars, for example. The method is applicable to both high-(>30 000) and low-(<30 000) resolution spectra, although the information that can be extracted from the latter is limited by the resolving power itself.

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“…represented as velocity moments) or as variations in intensity as a function of position in the line profiles. Accordingly, there are two methods available for analysing the pulsational characteristics of line profiles: the moment method (Briquet & Aerts 2003, and references therein) and Fourier parameter fit method (FPF, Zima 2006). Both methods assume a Gaussian intrinsic line profile.…”

Section: Search For the Oscillations In The Various Line Diagnosticsmentioning

confidence: 99%

Interpreting the line-profile variations of subdwarf B pulsators: the case of PG 1336-018 (NY Virginis)

Vučković¹,

Østensen²,

Aerts

et al. 2009

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Aims. We analyze the high-resolution time-resolved VLT/uves spectra of PG 1336−018, a rapidly pulsating subdwarf B (sdB) primary in a close orbit with an M5 companion, with the aim to detect the pulsational signal of the primary in line-profile variations. Methods. After removing the dominant radial-velocity component inherent to the orbital motion and taking only out-of-eclipse data we computed cross-correlation functions (CCFs) for each individual spectrum and assumed these to approximate the average line profile. We computed predictions of line-profile variations for pulsating sdB stars and present their diagnostic value for mode identification. Results. We detect the pulsation mode at 5435 μHz in the line-profile variations of the CCFs which allows us to characterize the detected pulsation mode of PG 1336−018. Conclusions. We model the pulsational perturbations of synthetic spectra for a star with physical parameters like PG 1336−018 and confront them with the observed spectra. We find that low order Balmer lines can be used as diagnostic tool to identify pulsation modes. A detailed line-profile analysis of the perturbed time-series spectra excludes the = |m| = (3, 3), (1, 0), (2, 1) and (2, 0) modes, but does not allow a unique mode identification among the radial or sectoral dipole or quadrupole modes.

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A new version of the moment method, optimized for mode identification in multiperiodic stars

Cited by 84 publications

References 13 publications

Gravito-inertial and pressure modes detected in the B3 IV CoRoT target HD 43317

Gravito-inertial and pressure modes detected in the B3 IV CoRoT target HD 43317

Denoising spectroscopic data by means of the improved least-squares deconvolution method

Interpreting the line-profile variations of subdwarf B pulsators: the case of PG 1336-018 (NY Virginis)

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