Time-resolved H-alpha spectroscopy of the Be star PLEIONE during a lunar occultation

Gies, Douglas R.; McKibben, William P.; Kelton, Phillip W.; Opal, C. B.; Sawyer, S. R.

doi:10.1086/115620

Cited by 46 publications

(71 citation statements)

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“…However, its existence seems possible. Evidence for the presence of this kind of asymmetric envelope was reported for Pleione (Gies et al 1990), through Hα spectroscopy during a lunar occultation. An envelope of a mean radius of 34 to 55 stellar radii was estimated for this star and the asymmetry of the envelope was attributted to the presence of a companion, detected by speckle interferometry.…”

Section: Time Variationsmentioning

confidence: 75%

The circumstellar environment of the star V923 Aquilae

Arias

Cidale

Ringuelet

2004

A&A

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Abstract. V923 Aquilae is a Be shell star that displays emission in Hα, cyclic V/R variations and variations in the intensity of the near infrared continuum. The star presents radial velocity variations arising from a superposition of a long-term cycle and an orbital motion with a period of 214.756 days (Koubský et al. 1989). To investigate the physical properties and the geometry of the circumstellar envelope of this star, we have analysed its spectra in the UV and visual range. We have selected Fe  lines to derive temperatures and location of the line-forming regions. Our results indicate that the dimensions of the circumstellar envelope vary with time and this variation correlates with the orbital period of 214.75 days. On the other hand, we determined a period of 6.8 years for V/R cyclic variations in Hα. This period is in accordance with the long-term cycle in the radial velocity and U band photometric observations. We suggest that the V/R variability in the Hα line is linked to the behavior of the subsonic wind structure.

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Section: Time Variationsmentioning

confidence: 75%

The circumstellar environment of the star V923 Aquilae

Arias

Cidale

Ringuelet

2004

A&A

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“…22 was indeed discovered from speckle interferometry by McAlister et al (1989). Gies et al (1990) studied a sequence of low-dispersion Hα spectra of BU Tau taken with a sampling rate of 7 ms during a lunar occultation on 1987 March 6. They detected an asymmetry of the envelope in A&A 516, A80 (2010) agreement with the observed long-term V/R changes.…”

Section: Introductionmentioning

confidence: 94%

Properties and nature of Be stars

Nemravová¹,

Harmanec²,

Kubát

et al. 2010

A&A

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Radial-velocity variations of the Hα emission measured on the steep wings of the Hα line, prewhitened for the long-time changes, vary periodically with a period of 218. d 025 ±0. d 022, confirming the suspected binary nature of the bright Be star BU Tau, a member of the Pleiades cluster. The orbit seems to have a high eccentricity over 0.7, but we also briefly discuss the possibility that the true orbit is circular and that the eccentricity is spurious owing to the phase-dependent effects of the circumstellar matter. The projected angular separation of the spectroscopic orbit is large enough to allow the detection of the binary with large optical interferometers, provided the magnitude difference primary − secondary is not too large. Since our data cover the onset of a new shell phase up to development of a metallic shell spectrum, we also briefly discuss the recent long-term changes. We confirm the formation of a new envelope, coexisting with the previous one, at the onset of the new shell phase. We find that the full width at half maximum of the Hα profile has been decreasing with time for both envelopes. In this connection, we briefly discuss Hirata's hypothesis of precessing gaseous disk and possible alternative scenarios of the observed long-term changes.

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“…These changes can be due either to variations in the physical structure and size of a more or less permanent circumstellar environment (CE), or the creation of a new CE during mass ejection events of the central star. Interferometric and linear-polarization measurements place observational constraints on the CE flattening (Gies et al 1990;Stee et al 1994;Quirrenbach et al 1997;Yudin 2001;Tycner 2004). Nevertheless, the disk formation and its geometry is still poorly known, but the situation is changing rapidly with the recent CHARA (Gies et al 2007), NPOI (Tycner et al 2006), and VLTI interferometric measurements (Meilland et al 2007).…”

Section: Introductionmentioning

confidence: 99%

Disk and wind evolution of Achernar: the breaking of the fellowship

Kanaan

Meilland

Stee

et al. 2008

A&A

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Aims. We use spectral energy distributions (SEDs), Hα line profiles, and visibilities available in the literature to study Achernar's envelope geometry and to propose a possible scenario for its circumstellar disk formation and dissipation. Methods. We use the SIMECA code to investigate possible geometries of the circumstellar environment by comparing our synthetic results with spectroscopic and high angular resolution data from the VLTI/VINCI instrument. We compute three different kinds of models: an equatorial disk, a polar wind, and a disk+wind model. Results. We develop a 2D axial symmetric kinematic model to study the variation of the observed Hα line profiles, which provides clear evidence of Achernar's equatorial disk formation and dissipation between 1991 and 2002. Our model can reproduce the polarwind extension greater than 10 R and a possible equatorial disk (≤5 R ) but we were unable to estimate the wind opening angle. We reproduce the Hα line-profile variations using an outburst scenario, but the disk final contraction requieres an additional physical effect to be taken into account. The polar stellar wind does not appear to be linked to the presence of a disk or a ring around the star. We test the possibility of a binary companion to Achernar, as found by Kervella & Domiciano de Souza (2007, A&A, 474, L49), but conclude that the VLTI/VINCI visibilities cannot be explained by a rotationally-distorted Be star and a companion alone. The presence of a polar jet provides an important component to reproduce the observations even if it is not excluded that the companion could partially influence the observations. New interferometric observations at short baselines (5 ≤ B ≤ 20 m) are mandatory to constrain Achernar's circumstellar envelope, as well as spectroscopic long-term follow-up observational programs to link Achernar's mass-loss episodes with its circumstellar disk formation.

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Time-resolved H-alpha spectroscopy of the Be star PLEIONE during a lunar occultation

Cited by 46 publications

References 0 publications

The circumstellar environment of the star V923 Aquilae

The circumstellar environment of the star V923 Aquilae

Properties and nature of Be stars

Disk and wind evolution of Achernar: the breaking of the fellowship

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