Non-radially pulsating Be stars

Rivinius, Thomas; Baade, D.; Štefl, S.

doi:10.1051/0004-6361:20031285

Cited by 148 publications

(212 citation statements)

References 52 publications

Supporting

Mentioning

192

Contrasting

Unclassified

Order By: Relevance

“…There are pre-main-sequence Herbig Be stars (usually grouped with the Ae stars), there are binary mass transfer systems where circumstellar emission occurs, and there is a large class of stars that are rapidly rotating and have occasional outbursts where material is launched from the stellar surface into a disk, thus producing emission lines. Members of the latter group have been shown to be pulsating stars (Rivinius, Baade &Štefl 2003) and a model has been proposed by Dylan Kee et al (2014) of how pulsation, coupled with rapid, but sub-critical rotation, can launch material into orbit. During the outbursts of pulsational Be stars the pulsation amplitude increases.…”

Section: Be Starsmentioning

confidence: 99%

A unifying explanation of complex frequency spectra of γ Dor, SPB and Be stars: combination frequencies and highly non-sinusoidal light curves

Kurtz¹,

Shibahashi²,

Murphy³

et al. 2015

Monthly Notices of the Royal Astronomical Society

146

199

View full text Add to dashboard Cite

There are many Slowly Pulsating B (SPB) stars and γ Dor stars in the Kepler Mission data set. The light curves of these pulsating stars have been classified phenomenologically into stars with symmetric light curves and with asymmetric light curves. In the same effective temperature ranges as the γ Dor and SPB stars, there are variable stars with downward light curves that have been conjectured to be caused by spots. Among these phenomenological classes of stars, some show 'frequency groups' in their amplitude spectra that have not previously been understood. While it has been recognised that nonlinear pulsation gives rise to combination frequencies in a Fourier description of the light curves of these stars, such combination frequencies have been considered to be a only a minor constituent of the amplitude spectra. In this paper we unify the Fourier description of the light curves of these groups of stars, showing that many of them can be understood in terms of only a few base frequencies, which we attribute to g mode pulsations, and combination frequencies, where sometimes a very large number of combination frequencies dominate the amplitude spectra. The frequency groups seen in these stars are thus tremendously simplified. We show observationally that the combination frequencies can have amplitudes greater than the base frequency amplitudes, and we show theoretically how this arises. Thus for some γ Dor and SPB stars combination frequencies can have the highest observed amplitudes. Among the B stars are pulsating Be stars that show emission lines in their spectra from occasional ejection of material into a circumstellar disk. Our analysis gives strong support to the understanding of these pulsating Be stars as rapidly rotating SPB stars, explained entirely by g mode pulsations.

show abstract

Section: Be Starsmentioning

confidence: 99%

A unifying explanation of complex frequency spectra of γ Dor, SPB and Be stars: combination frequencies and highly non-sinusoidal light curves

Kurtz¹,

Shibahashi²,

Murphy³

et al. 2015

Monthly Notices of the Royal Astronomical Society

146

199

View full text Add to dashboard Cite

show abstract

“…The simultaneous, let alone long-term, presence of both Fe iii and Mg i shell absorption is very unusual. A search of the large FLASH, HEROS, and FEROS database of Be spectra (Rivinius et al 2003) furnished no second example.…”

Section: Triple-peak Hα Profilesmentioning

confidence: 99%

Cyclic variability of the circumstellar disk of the Be starζ Tauri

Štefl¹,

Rivinius²,

Carciofi

et al. 2009

A&A

Self Cite

View full text Add to dashboard Cite

Context. Emission lines formed in decretion disks of Be stars often undergo long-term cyclic variations, especially in the violet-to-red (V/R) ratio of their primary components. The underlying structural and dynamical variations of the disks are only partly understood. From observations of the bright Be-shell star ζ Tau, the possibly broadest and longest data set illustrating the prototype of this behaviour was compiled from our own and archival observations. It comprises optical and infrared spectra, broad-band polarimetry, and interferometric observations. Aims. The dense, long-time monitoring permits a better separation of repetitive and ephemeral variations. The broad wavelength coverage includes lines formed under different physical conditions, i.e. different locations in the disk, so that the dynamics can be probed throughout much of the disk. Polarimetry and interferometry constrain the spatial structure. All together, the objective is a better understand the dynamics and life cycle of decretion disks. Methods. Standard methods of data acquisition, reduction, and analysis were applied. Results. From 3 V/R cycles between 1997 and 2008, a mean cycle length in Hα of 1400-1430 days was derived. After each minimum in V/R, the shell absorption weakens and splits into two components, leading to 3 emission peaks. This phase may make the strongest contribution to the variability in cycle length. There is no obvious connection between the V/R cycle and the 133-day orbital period of the not otherwise detected companion. V/R curves of different lines are shifted in phase. Lines formed on average closer to the central star are ahead of the others. The shell absorption lines fall into 2 categories differing in line width, ionization/excitation potential, and variability of the equivalent width. They seem to form in separate regions of the disk, probably crossing the line of sight at different times. The interferometry has resolved the continuum and the line emission in Brγ and HeI 2.06. The phasing of the Brγ emission shows that the photocenter of the line-emitting region lies within the plane of the disk but is offset from the continuum source. The plane of the disk is constant throughout the observed V/R cycles. The observations lay the foundation for the fully self-consistent, one-armed, disk-oscillation model developed in Paper II.

show abstract

“…It is still unknown what is the exact origin of mass ejection from the stellar surface. The most probable scenario is that mass is ejected due to instabilities caused by non-radial pulsations (NRP; Rivinius et al 2003), in a probably non-continuous and non-isotropical manner. The NRP frequencies are connected to the short-term variability of Be stars (Baade et al 2016), probably because of the non-axisymmetric ejections of mass that they cause.…”

Section: Discussionmentioning

confidence: 99%

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

View full text Add to dashboard Cite

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.

show abstract

Non-radially pulsating Be stars

Cited by 148 publications

References 52 publications

A unifying explanation of complex frequency spectra of γ Dor, SPB and Be stars: combination frequencies and highly non-sinusoidal light curves

A unifying explanation of complex frequency spectra of γ Dor, SPB and Be stars: combination frequencies and highly non-sinusoidal light curves

Cyclic variability of the circumstellar disk of the Be starζ Tauri

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

Contact Info

Product

Resources

About