On the Nature of the Central Source in η Carinae

Hillier, D. J.; Davidson, Kris; Ishibashi, Koji; Gull, Theodore R.

doi:10.1086/320948

Cited by 331 publications

(657 citation statements)

References 69 publications

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“…A&A 594, A106 (2016) First spectro-interferometric VLTI-AMBER observations of η Car ) with medium and high spectral resolution in the He i 2.059 µm and the Brγ 2.166 µm emission lines allowed us to study the spatial structure of η Car's wind as a function of wavelength with a high spatial resolution of ∼5 mas and spectral resolutions of 1500 and 12 000. The measured line visibilities agree with predictions of the radiative transfer model of Hillier et al (2001). We derived 50% encircled-intensity diameters of 4.2 mas (9.9 au), 6.5 mas (15.3 au), and 9.6 mas (22.6 au) in the 2.17 µm continuum, the He i 2.059 µm, and the Brγ 2.166 µm emission lines, respectively (for comparison, the radius R * of the primary star of η Car is ∼ 100 R ∼ 0.47 au ∼ 0.20 mas; however, R * is not known well; Hillier et al 2001).…”

Section: Introductionsupporting

confidence: 70%

VLTI-AMBER velocity-resolved aperture-synthesis imaging ofηCarinae with a spectral resolution of 12 000

Weigelt

Hofmann

Schertl

et al. 2016

A&A

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Context. The mass loss from massive stars is not understood well. η Carinae is a unique object for studying the massive stellar wind during the luminous blue variable phase. It is also an eccentric binary with a period of 5.54 yr. The nature of both stars is uncertain, although we know from X-ray studies that there is a wind-wind collision whose properties change with orbital phase. Aims. We want to investigate the structure and kinematics of η Car's primary star wind and wind-wind collision zone with a high spatial resolution of ∼6 mas (∼14 au) and high spectral resolution of R = 12 000. Methods. Observations of η Car were carried out with the ESO Very Large Telescope Interferometer (VLTI) and the AMBER instrument between approximately five and seven months before the August 2014 periastron passage. Velocity-resolved aperture-synthesis images were reconstructed from the spectrally dispersed interferograms. Interferometric studies can provide information on the binary orbit, the primary wind, and the wind collision.Results. We present velocity-resolved aperture-synthesis images reconstructed in more than 100 different spectral channels distributed across the Brγ 2.166 µm emission line. The intensity distribution of the images strongly depends on wavelength. At wavelengths corresponding to radial velocities of approximately −140 to −376 km s −1 measured relative to line center, the intensity distribution has a fan-shaped structure. At the velocity of −277 km s −1 , the position angle of the symmetry axis of the fan is ∼126 • . The fan-shaped structure extends approximately 8.0 mas (∼18.8 au) to the southeast and 5.8 mas (∼13.6 au) to the northwest, measured along the symmetry axis at the 16% intensity contour. The shape of the intensity distributions suggests that the obtained images are the first direct images of the innermost wind-wind collision zone. Therefore, the observations provide velocity-dependent image structures that can be used to test three-dimensional hydrodynamical, radiative transfer models of the massive interacting winds of η Car.

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Section: Introductionsupporting

confidence: 70%

VLTI-AMBER velocity-resolved aperture-synthesis imaging ofηCarinae with a spectral resolution of 12 000

Weigelt

Hofmann

Schertl

et al. 2016

A&A

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“…Those parameters that are not directly determined from non-LTE model atmosphere analysis -for example wind parameters derived from present day nebular properties -are given in italics. Due to the extreme mass loss rate for η Car a degeneracy is present for the stellar radius and temperature (Hillier et al 2001). References used in the construction of this table are a Clark et al (2003a) …”

Section: Afgl 2298 In the Context Of Lbv Eruptionsmentioning

confidence: 99%

Bolometric luminosity variations in the luminous blue variable AFGL2298

Clark¹,

Crowther

Larionov

et al. 2009

A&A

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Aims. We characterise the variability in the physical properties of the luminous blue variable AFGL 2298 (IRAS 18576+0341) between 1989−2008. Methods. In conjunction with published data from 1989−2001, we have undertaken a long term (2001−2008) near-IR spectroscopic and photometric observational campaign for this star and utilise a non-LTE model atmosphere code to interpret these data. Results. We find AFGL 2298 to have been highly variable during the two decades covered by the observational datasets. Photometric variations of ≥1.6 mag have been observed in the JHK wavebands; however, these are not accompanied by correlated changes in near-IR colour. Non-LTE model atmosphere analysis of 4 epochs of K band spectroscopy obtained between 2001−7 suggests that the photometric changes of AFGL 2298 were driven by expansion and contraction of the stellar photosphere accompanied by comparatively small changes in the stellar temperature (ΔT * ∼ 4.5 kK). Unclumped mass loss rates throughout this period were modest and directly comparable to those of other highly luminous (candidate) LBVs. However, the main finding of this analysis was that the bolometric luminosity of AFGL 2298 appears to have varied by at least a factor of ∼2 between 1989−2008, with it being one of the most luminous stars in the Galaxy during maximum. Comparison to other LBVs that have undergone non bolometric luminosity conserving "eruptions" shows such events to be heterogeneous, with AFGL 2298 the least extreme example. These results -and the diverse nature of both the quiescent LBVs and associated ejecta -may offer support to the suggestion that more than one physical mechanism is responsible for such behaviour.

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“…Based on the results of Pittard & Corcoran (2002) the secondary's wind speed is taken to be v 2 ¼ 3000 km s À1 , and the mass-loss rates are assumed to beṀ 1 ¼ 3 ; 10 À4 M yr À1 andṀ 2 ¼ 10 À5 M yr À1 . The masses are M 1 ¼ 120 M and M 2 ¼ 30 M (Hillier et al 2001), the eccentricity is e ¼ 0:9 (Smith et al 2004), and the orbital period is 2024 days; hence, the semimajor axis is a ¼ 16:64 AU.…”

Section: Numerical Valuesmentioning

confidence: 99%

“…The orbit is believed to have a very high eccentricity. For primary and secondary masses of M 1 ¼ 120 M and M 2 ¼ 30 M , respectively, the semimajor axis of the orbit is a ¼ 16:6 AU (there is not yet agreement on all the binary parameters, e.g., Ishibashi et al 1999;Damineli et al 2000;Corcoran et al 2001aCorcoran et al , 2004aHillier et al 2001;Pittard & Corcoran 2002;Smith et al 2004).…”

Section: Introductionmentioning

confidence: 99%

Accretion by the Secondary in η Carinae During the Spectroscopic Event. I. Flow Parameters

Soker

2005

ApJ

120

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We examine the influence of the gravity of the companion (the secondary) to the massive primary star Carinae on the winds blown by the primary and the secondary. The two winds collide with each other after passing through two respective shock waves, and escape the system while strongly emitting in the X-ray band. While during most of the 5.5 yr orbital period the companion's gravity has a negligible effect on the winds, we find that near periastron the companion's gravity may significantly influence the flow, and the companion might accrete from the primary's wind under certain circumstances. Near periastron passage, the collision region of the two winds may collapse onto the secondary star, a process that could substantially reduce the X-ray luminosity. We suggest that such an accretion process produces the long, almost flat, X-ray minimum in Car.

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On the Nature of the Central Source in η Carinae

Cited by 331 publications

References 69 publications

VLTI-AMBER velocity-resolved aperture-synthesis imaging ofηCarinae with a spectral resolution of 12 000

VLTI-AMBER velocity-resolved aperture-synthesis imaging ofηCarinae with a spectral resolution of 12 000

Bolometric luminosity variations in the luminous blue variable AFGL2298

Accretion by the Secondary in η Carinae During the Spectroscopic Event. I. Flow Parameters

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