The shape of <i>η</i> Carinae and LBV nebulae

Maeder, A.; Desjacques, Vincent

doi:10.1051/0004-6361:20010539

Cited by 65 publications

(63 citation statements)

References 20 publications

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“…Van Boekel's and our continuum elongation measurements favor the physical model according to which η Car exhibits an enhanced mass loss in polar direction as proposed, for instance, by Owocki et al (1996Owocki et al ( , 1998 or Maeder & Desjacques (2001) for stars rotating close to their critical rotation speed. Axis ratios of the order of 1.2 appear reasonable in the context of such polar-wind models.…”

Section: Elongated Shape Of the Continuum Intensity Distributionsupporting

confidence: 88%

Near-infrared interferometry of η Carinae with spectral resolutions of 1 500 and 12 000 using AMBER/VLTI

Weigelt

Kraus

Driebe

et al. 2006

A&A

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Aims. We present the first NIR spectro-interferometry of the LBV η Carinae. The observations were performed with the AMBER instrument of the ESO Very Large Telescope Interferometer (VLTI) using baselines from 42 to 89 m. The aim of this work is to study the wavelength dependence of η Car's optically thick wind region with a high spatial resolution of 5 mas (11 AU) and high spectral resolution. Methods. The observations were carried out with three 8.2 m Unit Telescopes in the K-band. The raw data are spectrally dispersed interferograms obtained with spectral resolutions of 1500 (MR-K mode) and 12 000 (HR-K mode). The MR-K observations were performed in the wavelength range around both the He i 2.059 µm and the Brγ 2.166 µm emission lines, the HR-K observations only in the Brγ line region.Results. The spectrally dispersed AMBER interferograms allow the investigation of the wavelength dependence of the visibility, differential phase, and closure phase of η Car. In the K-band continuum, a diameter of 4.0 ± 0.2 mas (Gaussian FWHM, fit range 28-89 m baseline length) was measured for η Car's optically thick wind region. If we fit Hillier et al. (2001, ApJ, 553, 837) model visibilities to the observed AMBER visibilities, we obtain 50% encircled-energy diameters of 4.2, 6.5 and 9.6 mas in the 2.17 µm continuum, the He i, and the Brγ emission lines, respectively. In the continuum near the Brγ line, an elongation along a position angle of 120• ±15• was found, consistent with previous VINCI/VLTI measurements by van Boekel et al. (2003, A&A, 410, L37). We compare the measured visibilities with predictions of the radiative transfer model of Hillier et al. (2001), finding good agreement. Furthermore, we discuss the detectability of the hypothetical hot binary companion. For the interpretation of the non-zero differential and closure phases measured within the Brγ line, we present a simple geometric model of an inclined, latitude-dependent wind zone. Our observations support theoretical models of anisotropic winds from fast-rotating, luminous hot stars with enhanced high-velocity mass loss near the polar regions.

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Section: Elongated Shape Of the Continuum Intensity Distributionsupporting

confidence: 88%

Near-infrared interferometry of η Carinae with spectral resolutions of 1 500 and 12 000 using AMBER/VLTI

Weigelt

Kraus

Driebe

et al. 2006

A&A

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“…Kep is the Keplerian velocity on the equator (i.e., the breakup angular velocity). Dwarkadas & Owocki (2002) and Smith et al (2003a), for example, take ¼ 0:9, while Maeder & Desjacques (2001) take ¼ 0:8 0:9. The model presented by Langer et al (1999) is different in that they consider the ratio of luminosity to the Eddington limit.…”

Section: Angg Ular Velocity Evv Olution Duringgthe Great Eruptionmentioning

confidence: 99%

Why a Single‐Star Model Cannot Explain the Bipolar Nebula of η Carinae

Soker

2004

ApJ

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I examine the angular momentum evolution during the 1837-1856 Great Eruption of the massive star Carinae. I find that the new estimate of the mass blown during that eruption implies that the envelope of Car substantially spun down during the 20 yr eruption. Single-star models, most of which require the envelope to rotate at close to the break-up velocity, cannot account for the bipolar nebula-the Homunculus-formed from matter expelled in that eruption. The kinetic energy and momentum of the Homunculus further constrain singlestar models. I discuss how Car can fit into a unified model for the formation of bipolar lobes in which two oppositely ejected jets inflate two lobes (or bubbles). These jets are blown by an accretion disk, which requires stellar companions in the case of bipolar nebulae around stellar objects.

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“…Interestingly enough, the group of the B[e] stars shows a two-component stellar wind with a hot, highly ionized, fast wind at the poles and a slow, dense, disk-like wind at the equator (Zickgraf 1989). Maeder & Desjacques (2001) have noticed that the polar lobes and skirt in η Carinae and other LBV stars may naturally result from the g eff and κ-effects. Langer et al (1999) have shown that giant LBV outbursts depend on the initial rotation rate.…”

Section: Results Of Numerical Calculationmentioning

confidence: 99%

Structure and evolution of rotationally and tidally distorted stars

Song

Zhong

Lü

2009

A&A

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Aims. This paper aims to study the configuration of two components caused by rotational and tidal distortions in the model of a binary system. Methods. The potentials of the two distorted components can be approximated to 2nd-degree harmonics. Furthermore, both the accretion luminosity (σ i ) and the irradiative luminosity are included in stellar structure equations. Results. The equilibrium structure of rotationally and tidally distorted star is exactly a triaxial ellipsoids. A formula describing the isobars is presented, and the rotational velocity and the gravitational acceleration at the primary surface simulated. The results show the distortion at the outer layers of the primary increases with temporal variation and system evolution. Besides, it was observed that the luminosity accretion is unstable, and the curve of the energy-generation rate fluctuates after the main sequence in rotation sequences. The luminosity in rotation sequences is slightly weaker than that in non-rotation sequences. As a result, the volume expands slowly. Polar ejection is intensified by the tidal effect. The ejection of an equatorial ring may be favoured by both the opacity effect and the g e (θ, ϕ)-effect in the binary system.

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The shape of η Carinae and LBV nebulae

Cited by 65 publications

References 20 publications

Near-infrared interferometry of η Carinae with spectral resolutions of 1 500 and 12 000 using AMBER/VLTI

Near-infrared interferometry of η Carinae with spectral resolutions of 1 500 and 12 000 using AMBER/VLTI

Why a Single‐Star Model Cannot Explain the Bipolar Nebula of η Carinae

Structure and evolution of rotationally and tidally distorted stars

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