Classical Be stars

Rivinius, Thomas; Carciofi, A. C.; Martayan, Christophe

doi:10.1007/s00159-013-0069-0

Cited by 555 publications

(723 citation statements)

References 257 publications

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“…This intermediate value of viscosity was chosen so that both the difference in the line profiles can be seen (lower values of αss do not have a double-peaked profile even at i as large as 60 • in the spatial resolution of the SPH simulations; Figure 5a) and the V/R variability amplitude is sufficiently large at i = 90 • (it is small at higher αss; Figure 5d). The results for the emission at different inclinations in general agree with the sample spectra given in figure 1 of Rivinius et al (2013) for the line emissions of Be discs. The i = 90 • curve of Figure 5i confirms that the line profile of an edge-on star is that of a shell star (i.e.…”

Section: Radiative Transfer Calculationssupporting

confidence: 85%

Be discs in coplanar circular binaries: Phase-locked variations of emission lines

Panoglou

Faes

Carciofi

et al. 2017

Monthly Notices of the Royal Astronomical Society

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The first results of radiative transfer calculations on decretion discs of binary Be stars are presented. A smoothed particle hydrodynamics code computes the structure of Be discs in coplanar circular binary systems for a range of orbital and disc parameters. The resulting disc configuration consists of two spiral arms, and can be given as input into a Monte Carlo code, which calculates the radiative transfer along the line of sight for various observational coordinates. Making use of the property of steady disc structure in coplanar circular binaries, observables are computed as functions of the orbital phase. Orbital-phase series of line profiles are given for selected parameter sets under various viewing angles, to allow comparison with observations. Flat-topped profiles with and without superimposed multiple structures are reproduced, showing, for example, that triple-peaked profiles do not have to be necessarily associated with warped discs and misaligned binaries. It is demonstrated that binary tidal effects give rise to phase-locked variability of the violet-to-red (V/R) ratio of hydrogen emission lines. The V/R ratio exhibits two maxima per cycle; in certain cases those maxima are equal, leading to a clear new V/R cycle every half orbital period. This study opens a way in identifying binaries and in constraining the parameters of binary systems that exhibit phase-locked variations induced by tidal interaction with a companion star.

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Section: Radiative Transfer Calculationssupporting

confidence: 85%

Be discs in coplanar circular binaries: Phase-locked variations of emission lines

Panoglou

Faes

Carciofi

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…Be stars have long been known as rapid rotators (Struve 1931) and, accordingly, these stars are assumed to create their circumstellar disk or envelope thanks mainly to this rapid rotation. General properties of Be stars and mechanisms to build up their circumstellar envelopes (hereafter CE) or disks are reviewed by Rivinius et al (2013).…”

Section: Introductionmentioning

confidence: 99%

Critical study of the distribution of rotational velocities of Be stars

Zorec

Frémat

Souza

et al. 2016

A&A

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Context. Among intermediate-mass and massive stars, Be stars are the fastest rotators in the main sequence (MS) and, as such, these stars are a cornerstone to validate models of structure and evolution of rotating stars. Several phenomena, however, induce under-or overestimations either of their apparent Vsin i, or true velocity V. Aims. In the present contribution we aim at obtaining distributions of true rotational velocities corrected for systematic effects induced by the rapid rotation itself, macroturbulent velocities, and binarity. Methods. We study a set of 233 Be stars by assuming they have inclination angles distributed at random. We critically discuss the methods of Cranmer and Lucy-Richardson, which enable us to transform a distribution of projected velocities into another distribution of true rotational velocities, where the gravitational darkening effect on the Vsin i parameter is considered in different ways. We conclude that iterative algorithm by Lucy-Richardson responds at best to the purposes of the present work, but it requires a thorough determination of the stellar fundamental parameters. Results. We conclude that once the mode of ratios of the true velocities of Be stars attains the value V/V c 0.77 in the main-sequence (MS) evolutionary phase, it remains unchanged up to the end of the MS lifespan. The statistical corrections found on the distribution of ratios V/V c for overestimations of Vsin i, due to macroturbulent motions and binarity, produce a shift of this distribution toward lower values of V/V c when Be stars in all MS evolutionary stages are considered together. The mode of the final distribution obtained is at V/V c 0.65. This distribution has a nearly symmetric distribution and shows that the Be phenomenon is characterized by a wide range of true velocity ratios 0.3 V/V c 0.95. It thus suggests that the probability that Be stars are critical rotators is extremely low. Conclusions. The corrections attempted in the present work represent an initial step to infer indications about the nature of the Be-star surface rotation that will be studied in the second paper of this series.

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“…Specifically, we aim to characterize for the first time the mass loss rateṀ and the viscous diffusion coefficient α to the newly formed Be disk based on the VDD model (c.f. Rivinius et al 2013b, and references therein). According to this model, the CS disk surface density Σ(r) can be a function of time according to the Eq.…”

Section: The Recent Disk Activitymentioning

confidence: 99%

“…The investigation of the photosphere of Be stars, and of their circumstellar (CS) disks, has entered a new phase during last years, both observationally and theoretically. See Rivinius et al (2013b) for a review.…”

Section: Introductionmentioning

confidence: 99%

The photosphere and circumstellar environment of the Be star Achernar

et al. 2014

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Abstract. Achernar is a key target to investigate high stellar rotation and the Be phenonemon. It is also the hottest star for which detailed photospheric information is available. Here we report our results to determine the photospheric parameters of Achernar and evaluate how the emission of a Viscous Decretion Disk (VDD) around it would be observable. The analysis is based on interferometric data (PIONIER and AMBER at ESO-VLTI), complemented by spectroscopy and polarimetry for the circumstellar emission. For the first time fundamental parameters of a Be photosphere were determined. The presence of a residual disk at the quiescent phase and some characteristics of the new formed disk (2013 activity) are also discussed. This is rare opportunity to precisely determine the stellar brightness distribution and evaluate the evolution of a just formed Be disk.

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Classical Be stars

Cited by 555 publications

References 257 publications

Be discs in coplanar circular binaries: Phase-locked variations of emission lines

Be discs in coplanar circular binaries: Phase-locked variations of emission lines

Critical study of the distribution of rotational velocities of Be stars

The photosphere and circumstellar environment of the Be star Achernar

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