First direct detection of a Keplerian rotating disk   around the Be star $\mathsf{\alpha}$ Arae using AMBER/VLTI

Meilland, A.; Stee, Philippe; Vannier, M.; Millour, F.; Souza, A. Domiciano de; Malbet, Fabien; Martayan, Christophe; Paresce, Francesco; Petrov, R.; Richichi, A.; Spang, A.

doi:10.1051/0004-6361:20064848

Cited by 120 publications

(158 citation statements)

References 37 publications

(43 reference statements)

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“…5.3 to explain this effect. We see that the differential phase plots exhibit "S" shapes, which are clear signatures for rotating disks (Meilland et al 2007b). The absence of this "S" shape for the B 2 baseline observation of 48 Per perhaps comes from the B 2 baseline being oriented close to the direction of the stellar rotational axis so that no photocenter displacement, which produces a fringe phase shift, is expected in this direction.…”

Section: Data In the Differential Analysis Modementioning

confidence: 78%

Kinematics and geometrical study of the Be stars 48 Persei andψPersei with the VEGA/CHARA interferometer

Delaa

Stee

Meilland

et al. 2011

A&A

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Context. Five different physical processes might be responsible for the formation of decretion disks around Be stars: fast rotation of the star, stellar pulsations, binarity, stellar winds, and magnetic fields. Our observations indicate that fast rotation seems to produce a disk in Keplerian rotation, at least in the specific case of the two stars observed. We do not know if this observational result is a generality or not. Aims. We measure the size, orientation, shape, and kinematics of the disks around 2 Be stars, namely 48 Per and ψ Per. Methods. We used the VEGA/CHARA interferometer with a spectral resolution of 5000 to obtain spectrally dispersed visibility modulus and phases within the Hα emission line. Results. We were able to estimate the disk extension in the continuum and in the Hα line, as well as flattening, for both stars. Both stars rotate at nearly a critical rotation, but while the disk of 48 Per seems to be in Keplerian rotation, our preliminary data suggest that the disk of ψ Per is possibly faster than Keplerian, similarly to what has been found for κ CMa with observations carried out in the near-IR. However, more data is needed to confirm the fast rotation of the disk. Conclusions. Assuming a simple uniform disk model for the stellar photosphere in the continuum and a Gaussian brightness distribution in the line emission region, we obtain a ratio of the disk diameter over the photospheric diameter of 8 for 48 Per and 11 for and ψ Per. We also found that the major axis of 48 Per is parallel to the polarization angle and not perpendicular to it as previously observed for many Be stars, including ψ Per. This might be due to the optical thickness of the disk, which is also responsible for the incoherent scattering of a non negligible part of the Hα line emission. To our knowledge, this is the first time that this effect has been measured in a Be star.

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Section: Data In the Differential Analysis Modementioning

confidence: 78%

Kinematics and geometrical study of the Be stars 48 Persei andψPersei with the VEGA/CHARA interferometer

Delaa

Stee

Meilland

et al. 2011

A&A

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“…This observable has been intensively used to study the kinematic of circumstellar environments (e.g. Berio et al 1999;and Meilland et al 2007). In Figs.…”

Section: Structures At the Surfacementioning

confidence: 99%

Chromosphere of K giant stars

Bério

Merle

Thévenin

et al. 2011

A&A

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Context. Interferometers provide accurate diameter measurements of stars by analyzing both the continuum and the lines formed in photospheres and chromospheres. Tests of the geometrical extent of the chromospheres are therefore possible by comparing the estimated radius in the continuum of the photosphere and the estimated radii in chromospheric lines. Aims. We aim to constrain the geometrical extent of the chromosphere of non-binary K giant stars and detect any spatial structures in the chromosphere. Methods. We performed observations with the CHARA interferometer and the VEGA beam combiner at optical wavelengths. We observed seven non-binary K giant stars (β and η Cet, δ Crt, ρ Boo, β Oph, 109 Her, and ι Cep). We measured the ratio of the radii of the photosphere to the chromosphere using the interferometric measurements in the H α and the Ca II infrared triplet line cores. For β Cet, spectro-interferometric observations are compared to a non-local thermal equilibrium (NLTE) semi-empirical model atmosphere including a chromosphere. The NLTE computations provide line intensities and contribution functions that indicate the relative locations where the line cores are formed and can constrain the size of the limb-darkened disk of the stars with chromospheres. We measured the angular diameter of seven K giant stars and deduced their fundamental parameters: effective temperatures, radii, luminosities, and masses. We determined the geometrical extent of the chromosphere for four giant stars (β and η Cet, δ Crt and ρ Boo). Results. The chromosphere extents obtained range between 16% to 47% of the stellar radius. The NLTE computations confirm that the Ca II/849 nm line core is deeper in the chromosphere of β Cet than either of the Ca II/854 nm and Ca II/866 nm line cores. We present a modified version of a semi-empirical model atmosphere derived by fitting the Ca II triplet line cores of this star. In four of our targets, we also detect the signature of a differential signal showing the presence of asymmetries in the chromospheres. Conclusions. It is the first time that geometrical extents and structure in the chromospheres of non-binary K giant stars are determined by interferometry. These observations provide strong constrains on stellar atmosphere models.

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“…From CHARA/VEGA measurement to be published in Mourard et al (2014). Stee et al 2012 or radiative transfer codes such as SIMECA (Meilland et al 2007a, Meilland et al 2007b, BEDSIK (Tycner et al 2011), or HDUST (Štefl et al 2009). In all cases the authors found that the circumstellar emission stems from a thin equatorial disk.…”

Section: Mass Loss and Circumstellar Environmentsmentioning

confidence: 99%

An interferometric journey around massive stars

Meilland¹,

Stee²

2014

Proc. IAU

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Abstract. Since the construction in the late nineties of modern facilities such as the VLTI or CHARA, interferometry became a key technique to probe massive stars and their oftencomplex circumstellar environments. Over the last decade, the development of a new generation of beam combiners for these facilities enabled major breakthroughs in the understanding of the formation and evolution of massive stars. In this short review, we will present few of these advances concerning young stellar objects, binarity, mass loss, and stellar surfaces.

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First direct detection of a Keplerian rotating disk around the Be star $\mathsf{\alpha}$ Arae using AMBER/VLTI

Cited by 120 publications

References 37 publications

Kinematics and geometrical study of the Be stars 48 Persei andψPersei with the VEGA/CHARA interferometer

Kinematics and geometrical study of the Be stars 48 Persei andψPersei with the VEGA/CHARA interferometer

Chromosphere of K giant stars

An interferometric journey around massive stars

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