Spectroscopic variabilities in<i>λ</i>Pavonis

Levenhagen, R. S.; Leister, N. V.; Künzel, Roseli

doi:10.1051/0004-6361/201116590

Cited by 6 publications

(3 citation statements)

References 34 publications

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“…Since then, it has become a useful tool widely used by spectroscopists in the analysis of stellar spectra. Usually, only the linear and the quadractic laws are adopted when applying the Fourier method (Royer et al 2007;Reiners & Schmitt 2002Levenhagen et al 2011;Levenhagen et al 2013aLevenhagen et al , 2013b.…”

Section: Fourier Transforms Of Rotation Profiles Under Different Ld Lawsmentioning

confidence: 99%

A FOURIER TRANSFORM METHOD FORVsiniESTIMATIONS UNDER NONLINEAR LIMB-DARKENING LAWS

Levenhagen

2014

ApJ

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Star rotation offers us a large horizon for the study of many important physical issues pertaining to stellar evolution. Currently, four methods are widely used to infer rotation velocities, namely those related to line width calibrations, on the fitting of synthetic spectra, interferometry, and on Fourier transforms (FTs) of line profiles. Almost all of the estimations of stellar projected rotation velocities using the Fourier method in the literature have been addressed with the use of linear limb-darkening (LD) approximations during the evaluation of rotation profiles and their cosine FTs, which in certain cases, lead to discrepant velocity estimates. In this work, we introduce new mathematical expressions of rotation profiles and their Fourier cosine transforms assuming three nonlinear LD laws-quadratic, square-root, and logarithmic-and study their applications with and without gravity-darkening (GD) and geometrical flattening (GF) effects. Through an analysis of He i models in the visible range accounting for both limb and GD, we find out that, for classical models without rotationally driven effects, all the V sin i values are too close to each other. On the other hand, taking into account GD and GF, the V sin i obtained with the linear law result in V sin i values that are systematically smaller than those obtained with the other laws. As a rule of thumb, we apply these expressions to the FT method to evaluate the projected rotation velocity of the emission B-type star Achernar (α Eri).

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Section: Fourier Transforms Of Rotation Profiles Under Different Ld Lawsmentioning

confidence: 99%

A FOURIER TRANSFORM METHOD FORVsiniESTIMATIONS UNDER NONLINEAR LIMB-DARKENING LAWS

Levenhagen

2014

ApJ

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“…This work presents and describes our code ZPEKTR, which stands for 'von ZeiPEl's code for gravity darKening specTRal synthesis'. Levenhagen et al (2011) originally developed this code in C ANSI language, and after that, the name ZPEKTR, pronounced 'spectre', was chosen to avoid homonyms with other synthesis codes (Levenhagen 2014). Interpolation routines used within the code come from the Python SciPy library (Virtanen et al 2020), while we take numerical functions from NumPy (Harris et al 2020).…”

Section: Introductionmentioning

confidence: 99%

ZPEKTR: A code for spectral synthesis of fast-rotating stars

Levenhagen,

Curé,

Arcos

et al. 2024

A&A

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Estimating the physical states of the surfaces of fast-rotating stars is challenging due to several intrinsic processes, which include radiative flux inhomogeneities on the photosphere induced by rotation and circumstellar signatures in their spectra. The analysis of their spectra ultimately requires the use of synthetic grids of spectra accounting for all these physical processes. In this paper, we present the `von ZeiPEl's code for gravity darKening specTRal synthesis' (ZPEKTR) code, which is designed to perform the spectral synthesis of fast-rotating stars, accounting for gravity darkening, limb-darkening effects in the continuum and geometrical deformation induced by fast rotation. We consider colatitudinal temperature and surface-gravity variations, assuming both the classical prescription developed by von Zeipel and the new formulation by Espinosa-Lara. The code runs either with a rectangular or a triangular mesh on the stellar surface. We compare the temperature and gravitational distribution as a function of the stellar latitude arising from both models. The line profiles of 4388, 4471, 4922, and 6678 produced with both formalisms are compared at three different rotation rates and illustrate differences in shape and central intensity. We also illustrate the fittings of 31 line spectra of classical Be stars averaged from the Be Stars Observation Survey (BeSOS) database and make a comparison among their apparent physical parameters and ages determined from plane-parallel non-local thermodynamical equilibrium (non-LTE) models and parameters determined from classical von Zeipel models, finding a displacement of more evolved objects towards the zero-age main sequence. We also compare the distributions of projected rotation velocities of these objects obtained with and without the inclusion of gravity-darkening effects with ZPEKTR. We observe a shift of the histogram of rotation velocities calculated accounting for effects of gravity darkening concerning rotation velocities obtained through the fittings with classical plane-parallel non-LTE models. We show that models that do not account for gravity darkening can underestimate the rotation velocity, because the stellar latitudes that contribute the higher velocities are those in the equator with the least radiative flux. We envisage near-future improvements to the code, such as the inclusion of differential rotation and treatment of tidal forces in binary stellar systems.

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“…For instance, one-armed density oscillations (Okazaki 1997;Štefl et al 2009) usually result in variations from months to several years. The most frequent cause of disk variability is changes in the rate of AM injection from the central star into the disk, J, which manifests itself on all timescales from days to weeks (e.g., Carciofi et al 2007;Levenhagen et al 2011) to years and decades (Haubois et al 2012;Rímulo et al 2018). Finally, binarity effects are also an important source of intermediate-period disk variations (Panoglou et al 2018, and references therein).…”

Section: Introductionmentioning

confidence: 99%

A Multi-technique Study of the Dynamical Evolution of the Viscous Disk around the Be Star CMa

Ghoreyshi

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The observed emission lines of Be stars originate from a circumstellar Keplerian disk that are generally well explained by the Viscous Decretion Disk model. In an earlier work we performed the modeling of the full light curve of the bright Be star ω CMa (Ghoreyshi et al. 2018) with the 1-D time-dependent hydrodynamics code SINGLEBE and the Monte Carlo radiative-transfer code HDUST. We used the V-band light curve that probes the inner disk through four disk formation and dissipation cycles. This new study compares predictions of the same set of model parameters with time-resolved photometry from the near UV through the mid-infrared, comprehensive series of optical spectra, and optical broad-band polarimetry, that overall represent a larger volume of the disk. Qualitatively, the models reproduce the trends in the observed data due to the growth and decay of the disk. However, quantitative differences exist, e.g., an overprediction of the flux increasing with wavelength, too slow decreases in Balmer emission-line strength that are too slow during disk dissipation, and the discrepancy between the range of polarimetric data and the model. We find that a larger value of the viscosity parameter alone, or a truncated disk by a companion star, reduces these discrepancies by increasing the dissipation rate in the outer regions of the disk.

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Spectroscopic variabilities inλPavonis

Cited by 6 publications

References 34 publications

A FOURIER TRANSFORM METHOD FORVsiniESTIMATIONS UNDER NONLINEAR LIMB-DARKENING LAWS

A FOURIER TRANSFORM METHOD FORVsiniESTIMATIONS UNDER NONLINEAR LIMB-DARKENING LAWS

ZPEKTR: A code for spectral synthesis of fast-rotating stars

A Multi-technique Study of the Dynamical Evolution of the Viscous Disk around the Be Star CMa

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