Predicting the Outbursts of the Be Star µ Cen

Rivinius, Th.; Baade, D.; Štefl, S.; Stahl, O.; Wolf, B.; Kaufer, A.

doi:10.1007/978-3-540-68597-5_50

Cited by 113 publications

(164 citation statements)

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“…non-radial pulsations (Rivinius et al 1998), and long-term (several to tens of years) cyclical spectroscopic variability originating from one-armed density waves in the disk (Okazaki 1991;Stefl et al 2009). Arguably the most dramatic type of variability observed is the aperiodic "Be to normal B to Be" transition whereby classical Be stars dissipate (i.e., lose) their disks, and will often begin to regenerate a new disk after a period of relative quiescence (see, e.g., Underhill & Doazan 1982 and references therein).…”

Section: Introductionmentioning

confidence: 99%

DISK-LOSS AND DISK-RENEWAL PHASES IN CLASSICAL Be STARS. I. ANALYSIS OF LONG-TERM SPECTROPOLARIMETRIC DATA

Wisniewski

Draper

Bjorkman

et al. 2010

ApJ

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Classical Be stars are known to occasionally transition from having a gaseous circumstellar disk ("Be phase") to a state in which all observational evidence for the presence of these disks disappears ("normal B-star phase"). We present one of the most comprehensive spectropolarimetric views to date of such a transition for two Be stars, π Aquarii and 60 Cygni.The disk-loss episode of 60 Cyg was characterized by a generally monotonic decrease in emission strength over a timescale of ∼1000 days from the maximum V-band polarization to the minimum Hα equivalent width, consistent with the viscous timescale of the disk, assuming α ∼0.14. π Aqr's disk loss was episodic in nature and occurred over a timescale of ∼2440 days. An observed time lag between the behavior of the polarization and Hα in both stars indicates the disk clearing proceeded in an "inside-out" manner. We determine the position angle of the intrinsic polarization to be 166.• 7 ± 0.• 1 for π Aqr and 107.• 7 ± 0.• 4 for 60 Cyg, and model the wavelength dependence of the observed polarization during the quiescent diskless phase of each star to determine the interstellar polarization along the line of sight. Minor outbursts observed during the quiescent phase of each star shared similar lifetimes as those previously reported for μ Cen, suggesting that the outbursts represent the injection and subsequent viscous dissipation of individual blobs of material into the inner circumstellar environments of these stars. We also observe deviations from the mean intrinsic polarization position angle during polarization outbursts in each star, indicating deviations from axisymmetry. We propose that these deviations might be indicative of the injection (and subsequent circularization) of new blobs into the inner disk, either in the plane of the bulk of the disk material or in a slightly inclined (non-coplanar) orbit.

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Section: Introductionmentioning

confidence: 99%

DISK-LOSS AND DISK-RENEWAL PHASES IN CLASSICAL Be STARS. I. ANALYSIS OF LONG-TERM SPECTROPOLARIMETRIC DATA

Wisniewski

Draper

Bjorkman

et al. 2010

ApJ

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“…This is in marked contrast with /J, Cen in which there is no indication of period variability and the beat periods and phases are reconciled with outbursts several years prior to the lpv observations (Rivinius et al (1998c), Rivinius et al (1998d)) and also permit predictions of the future behaviour to be made (Rivinius et al (1998e)). The recent observations of o And by Sareyan et al (1998) are of particular interest.…”

Section: Mysteriously "Variable" Periodsmentioning

confidence: 85%

“…But -2 seems to be the best value for m, and £ is probably in the range 3-5 with £=3-4 reproducing the observations best. Cyclically repeating line-emission outbursts Mu Cen undergoes frequent outbursts with a common morphology (Rivinius et al (1998a); Rivinius et al, these proceedings). Matter is ejected above the stellar surface and possibly partly merges with a pre-existing Keplerian disk (for references concerning the Keplerian or non-Keplerian character of disks of Be stars and their discussion see J. Bjorkman, these proceedings).…”

Section: Pulsation-driven Mass Loss Events In Fj Centauri?mentioning

confidence: 99%

“…Multiperiodic line profile variability The line profile variability (lpv) of this star can be decomposed into at least 6 periods which could be determined to within nearly one part in 10,000 (Rivinius et al (1998b)). Two periods are near 0.28d whereas the other four cluster around 0.5 d. Furthermore, the latter four show a distinct pattern in that the difference between the two lowest and the two highest frequencies is 0.034 c/d each whereas the separation of the two middle frequencies is 0.017 c/d.…”

Section: Pulsation-driven Mass Loss Events In Fj Centauri?mentioning

confidence: 99%

“…On this basis, o And could be the most promising candidate to date for a similar behaviour as found in \x Cen. However, the confusing effect of additional, transient periods during outburst phases of Be stars (Rivinius et al 1998a, b;Stefl, these proceedings) must serve as a caveat. Since Sareyan et al (1998) adjusted the mean differential magnitude of o And to 0.0 mag, the actual relevance of this concern cannot be readily estimated.…”

Section: Mysteriously "Variable" Periodsmentioning

confidence: 99%

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Non-radial Pulsations of BA Supergiants and Be Stars

Baade

1999

International Astronomical Union Colloquium

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If observing time and number of photons are not the limit, it will probably be very difficult to find any Be star or BA supergiant that is not variable. Moreover, there is hardly any major set of observations that is not tempting to explain at least partly in terms of nonradial (g-mode) pulsations. Since a few years ago, such conjectures are also theoretically permissible because improved opacity calculations have established the classical к-mechanism as a viable source of pulsation driving (cf. Pamyatnykh, these proceedings).Contrary to Be stars, it can for any given BA supergiant nevertheless be arbitrarily difficult to diagnose nonradial pulsations (NRP’s) with certainty because they need to be detected against considerable background ‘noise’ of other physical processes, most of which are related to mass loss and/or rotation. To make things worse, there is some evidence that NRP’s can have some effect on the dynamics of the mass loss. On the other hand, variable and non-spherical winds is the subject of this Colloquium, and this paper is accordingly biased towards the interplay between pulsation and mass loss.

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Interactions in Massive Binary Stars as Seen by Interferometry

Millour¹,

Meilland²,

Stee³

et al. 2013

The Environments of the Sun and the Stars

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With the advent of large-collecting-area instruments, the number of objects that can be reached by optical long-baseline interferometry is steadily increasing. We present here a few results on massive binary stars, showing the interest of using this technique for studying the insight of interactions in these systems. Indeed, many massive stars with extended environments host, or are suspected to host, companion stars. These companions could have an important role in shaping the circumstellar environment of the system. These examples provide a view in which binarity could be an ingredient, among many others, for the activity of these stars.

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Predicting the Outbursts of the Be Star µ Cen

Cited by 113 publications

References 3 publications

DISK-LOSS AND DISK-RENEWAL PHASES IN CLASSICAL Be STARS. I. ANALYSIS OF LONG-TERM SPECTROPOLARIMETRIC DATA

DISK-LOSS AND DISK-RENEWAL PHASES IN CLASSICAL Be STARS. I. ANALYSIS OF LONG-TERM SPECTROPOLARIMETRIC DATA

Non-radial Pulsations of BA Supergiants and Be Stars

Interactions in Massive Binary Stars as Seen by Interferometry

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