η Carinae: Binarity Confirmed

Damineli, A.; Kaufer, A.; Wolf, B.; Stahl, O.; Lopes, D. F.; Araújo, F. X. de

doi:10.1086/312441

Cited by 136 publications

(206 citation statements)

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“…Optical spectroscopic observations unveiled a peculiar cyclic behaviour, showing regularly repeating excitation minima with a period of 5.53 years (Damineli et al 2000). A similar behaviour was also found at other wavelength bands, from radio to X-rays, which is commonly interpreted in terms of a highly eccentric binary model composed of an S Dor-type very luminous primary star, and an unseen early type secondary star.…”

Section: Introductionsupporting

confidence: 67%

“…The LECS image will not be discussed here, as this paper is devoted to the analysis of the compact hard component which dominates beyond ∼2 keV. The observation date corresponds to phase 1.457 of the spectral variation cycle of 5.53 yr (Damineli et al 2000), assuming Φ = 1 for the 1998.0 minimum. Figure 1 shows the MECS images of the region around η Car using photon events selected from three different energy bands, in order to trace the softer and harder X-ray sources in the field and to map the regions emitting in the 6.7 keV iron line.…”

Section: Observationsmentioning

confidence: 99%

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The high energy X-ray tail of $\mathsf{\eta}$ Car revealed by BeppoSAX

Viotti

Antonelli

Rossi

et al. 2004

A&A

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Abstract. We report on the June 2000 long (100 ks) BeppoSAX exposure that unveiled a new very high energy component of the X-ray spectrum of η Car above 10 keV extending to at least 50 keV. We find that the 2-150 keV spectrum is best reproduced by a thermal + non-thermal model. The thermal component dominates the 2-10 keV spectral range with kT h = 5.5 ± 0.3 keV and log NH h = 22.68 ± 0.01. The spectrum displays a prominent iron emission line centred at 6.70 keV. Its equivalent width of 0.94 keV, if produced by the thermal source, gives a slightly sub-solar iron abundance ([Fe/H] = −0.15 ± 0.02). The high energy tail above 10 keV is best fitted by a power law with a photon index of 2.42 ± 0.04. The integrated 13-150 keV luminosity of ∼12 L is comparable to that of the 2-10 keV thermal component (19 L ). The present result can be explained, in the η Car binary star scenario, by Comptonisation of low frequency radiation by high energy electrons, probably generated in the colliding wind shock front, or in instabilities in the wind of the S Dor primary star. It is possible that the high energy tail had largely weakened near the minimum of the 5.53 yr cycle. Probably, the thermal component has a longer recovery time like that of the highest excitation optical emission lines. Both features can be associated with the large absorption measured by BeppoSAX at phase 0.05.

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Section: Introductionsupporting

confidence: 67%

Section: Observationsmentioning

confidence: 99%

The high energy X-ray tail of $\mathsf{\eta}$ Car revealed by BeppoSAX

Viotti

Antonelli

Rossi

et al. 2004

A&A

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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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“…For instance, radio (Duncan et al 1995), millimetre (mm, Abraham et al 2005), optical (Damineli 1996;Damineli et al 2000), near-infrared (near-IR, Whitelock et al 1994Whitelock et al , 2004Damineli 1996), and X-ray (Corcoran 2005) observations, obtained over the past few decades, have unveiled the existence of a period of ∼2022.7 ± 1.3 days (Damineli et al 2008).…”

Section: Introductionmentioning

confidence: 99%

ηCarinae: a very large hadron collider

Farnier

Walter

Leyder

2010

A&A

109

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Context. η Carinae is the colliding wind binary with the highest mass-loss rate in our Galaxy and the only one in which hard X-ray emission has been detected. Aims. η Carinae is therefore a primary candidate to search for particle acceleration by probing its gamma-ray emission. Methods. We used the first 21 months of Fermi/LAT data to extract gamma-ray (0.2-100 GeV) images, spectra, and light-curves, then combined them with multi-wavelength observations to model the non-thermal spectral energy distribution. Results. A bright gamma-ray source is detected at the position of η Carinae. Its flux at a few 100 MeV can be modelled by an extrapolation of the hard X-ray spectrum towards higher energies. The spectral energy distribution features two distinct components. The first one extends from the keV to GeV energy range, and features an exponential cutoff at ∼1 GeV. It can be understood as inverse Compton scattering of ultraviolet photons by electrons accelerated up to γ ∼ 10 4 in the colliding wind region. The expected synchrotron emission is compatible with the existing upper limit to the non-thermal radio emission. The second component is a hard gamma-ray tail detected above 20 GeV. It could be explained by π 0 -decay of accelerated hadrons interacting with the dense stellar wind. The ratio of the fluxes of the π 0 to inverse Compton components is roughly as predicted by simulations of colliding wind binaries. This hard gamma-ray tail can only be understood if emitted close to the wind collision region. The energy transferred to the accelerated particles (∼5% of the collision mechanical energy) is comparable to that of the thermal X-ray emission. Conclusions. The electron spectrum responsible for the keV to GeV emission was modelled and the observed emission above 20 GeV strongly suggests hadronic acceleration in η Carinae. These observations are thus in good agreement with the colliding wind scenario proposed for η Carinae.

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η Carinae: Binarity Confirmed

Cited by 136 publications

References 10 publications

The high energy X-ray tail of $\mathsf{\eta}$ Car revealed by BeppoSAX

The high energy X-ray tail of $\mathsf{\eta}$ Car revealed by BeppoSAX

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

ηCarinae: a very large hadron collider

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