Eta Carinae: a long period binary?

Damineli, A.; Conti, Peter S.; Lopes, D. F.

doi:10.1016/s1384-1076(97)00008-0

Cited by 172 publications

(187 citation statements)

References 21 publications

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“…Damineli (1996) first noted a 5.5 yr period in the variability of the He I 10830Å line. Further photometric and radial velocity studies (Damineli et al 1997(Damineli et al , 2000, X-ray observations (Tsuboi et al 1997;Corcoran et al 2000 and references therein), and radio data (Duncan et al 1995(Duncan et al , 1999 have supported the 5.5 yr period and the binary hypothesis. However, the ground based radial velocity curve was not confirmed by higher resolution spectra with STIS, indicating that at least the time of periastron passage is not well defined by the UV and optical spectra (Corcoran et al 2001a).…”

Section: Introductionmentioning

confidence: 88%

In hot pursuit of the hidden companion ofη Carinae: An X-ray determination of the wind parameters

Pittard

Corcoran

2002

A&A

228

386

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Abstract. We present X-ray spectral fits to a recently obtained Chandra grating spectrum of η Carinae, one of the most massive and powerful stars in the Galaxy and which is strongly suspected to be a colliding wind binary system. Hydrodynamic models of colliding winds are used to generate synthetic X-ray spectra for a range of mass-loss rates and wind velocities. They are then fitted against newly acquired Chandra grating data. We find that due to the low velocity of the primary wind (≈500 km s −1 ), most of the observed X-ray emission appears to arise from the shocked wind of the companion star. We use the duration of the lightcurve minimum to fix the wind momentum ratio at η = 0.2. We are then able to obtain a good fit to the data by varying the mass-loss rate of the companion and the terminal velocity of its wind. We find thatṀ 2 ≈ 10 −5 M yr −1 and v∞ 2 ≈ 3000 km s −1 . With observationally determined values of ≈500-700 km s −1 for the velocity of the primary wind, our fit implies a primary mass-loss rate ofṀ 1 ≈ 2.5 × 10 −4 M yr −1 . This value is smaller than commonly inferred, although we note that a lower mass-loss rate can reduce some of the problems noted by Hillier et al. (2001) when a value as high as 10 −3 M yr −1 is used. The wind parameters of the companion are indicative of a massive star which may or may not be evolved. The line strengths appear to show slightly sub-solar abundances, although this needs further confirmation. Based on the over-estimation of the X-ray line strengths in our model, and re-interpretation of the HST/FOS results, it appears that the Homunculus nebula was produced by the primary star.

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Section: Introductionmentioning

confidence: 88%

In hot pursuit of the hidden companion ofη Carinae: An X-ray determination of the wind parameters

Pittard

Corcoran

2002

A&A

228

386

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“…The "spectroscopic events", the X-ray observations and the spectroscopy suggest a colliding-wind binary (Damineli et al 1997(Damineli et al , 2000Pittard 2000). Another indication that η Car hides a secret is based on the detection of peculiar light variations of non-stellar origin, sometimes only clearly present in the near-UV, sometimes also detectable in V and B and deviating from the normal SD-variability.…”

Section: The Present Status Of η Carmentioning

confidence: 99%

“…The justification of serious doubt on the radial velocity curve of Damineli et al (1997) is certainly not new: two years before the study of Davidson et al (2000), de Groot & Henderson (1998, quoted by van Genderen et al 1999) already expressed their serious concern. They found that the HeI 5875Å and 6678Å lines (presumably originating deeper in the wind) gave radial velocities completely different from those on which the excisting binary models were based.…”

Section: The Present Status Of η Carmentioning

confidence: 99%

S Doradus variables in the Galaxy and the Magellanic Clouds

Genderen¹

2001

A&A

196

105

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Abstract. The goal in writing this paper is five fold: (1) to summarize the scientific achievements in the 20th century on S Dor variables (or LBVs); (2) to present an inventory of these variables in the Galaxy and the Magellanic Clouds with a description of their physical state and instability properties; (3) to emphasize the photometric achievements of the various types of instabilities. Generally this seems to be a neglected item resulting in a number of misunderstandings continuously wandering through literature; (4) to investigate the structure of the S Dor-area on the HR-diagram; (5) to estimate the total numbers of S Dor variables in the three stellar systems. The position of the strong active S Dor variables in minimum brightness obey the following linear relation on the HR-diagram:log L/L = 1.37 log T eff − 0.03. The relatively small dispersion of less active and supposed exand dormant S Dor variables with respect to this relation is twice as large at the blue side than at the red side. This might be caused by evolution to the WR stage and/or to high rotation. S Dor variables can be subject to five types of instabilities: the very rare genuine eruptive episodes (the "SD-eruptions"), two different brightening phases caused by slow pulsations (the "SD-phases"): one on a time scale of years, the other on a time scale of decades at a more or less constant luminosity and two types of microvariations: one on a time scale of weeks, the other on a time scale of about 100 d. So far, no periodicities of light curve characteristics of any of these instabilities have ever been found. The durations of active and non-active stages are estimated for about half of the sample based on scattered magnitude estimations such as from historical records, and on modern monitoring campaigns. It would be a misunderstanding to believe that all S Dor variables should be always spectacular. It is estimated that most of them will not be spectacular at all for at least 70% of their lifetime as an S Dor variable.

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“…Studies of the binary or binary wind-wind collision zone were reported by many authors (e.g., Damineli 1996;Damineli et al 1997Damineli et al , 1998Damineli et al , 2000Damineli et al , 2008bDavidson 1997;Davidson et al 2005Davidson et al , 2015Smith & Gehrz 2000;Smith et al 2004;Smith 2010;Pittard & Corcoran 2002;Corcoran et al 1997Corcoran et al , 2001Corcoran 2005;Ishibashi et al 1999;Soker 2003Soker , 2007Weis et al 2005;Gull et al 2006Gull et al , 2009Gull et al , 2011Gull et al , 2016Nielsen et al 2007;Weigelt et al 2007; Kashi & Soker 2007, 2009aParkin et al 2009;Groh et al 2010Groh et al , 2012bMadura & Owocki 2010;Madura et al 2012Madura et al , 2013Mehner et al 2010aMehner et al , 2011Mehner et al , 2012Mehner et al , 2015Richardson et al 2010;Teodoro et al 2013Teodoro et al , 2016Clementel et al 2015a,b;Hamaguchi et al 2016). The X-ray...…”

Section: Introductionmentioning

confidence: 99%

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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Eta Carinae: a long period binary?

Cited by 172 publications

References 21 publications

In hot pursuit of the hidden companion ofη Carinae: An X-ray determination of the wind parameters

In hot pursuit of the hidden companion ofη Carinae: An X-ray determination of the wind parameters

S Doradus variables in the Galaxy and the Magellanic Clouds

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

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