A multispectral view of the periodic events in η Carinae

Damineli, A.; Hillier, D. J.; Corcoran, M. F.; Stahl, O.; Groh, J. H.; Arias, J. I.; Teodoro, Mairan; Morrell, N.; Gamen, R.; González, F.; Leister, N. V.; Levato, H.; Levenhagen, R. S.; Grosso, M.; Colombo, J. F. Albacete; Wallerstein, George

doi:10.1111/j.1365-2966.2008.13214.x

Cited by 78 publications

(143 citation statements)

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“…B.2). The cause of this offset is unknown, but the high negative velocity and location of this high-velocity structure suggest that the emitting region is located in the innermost region of the wind collision cavity (Damineli et al 2008a;Groh et al 2010), because both the secondary star and the innermost region of the wind-wind collision cavity were located to the NW of the center of the continuum image at the phase of our observations. At high positive radial velocities (e.g., +250 to +350 km s −1 ), the reconstructed Brγ images show a much narrower wind intensity distribution than at high negative radial velocities (e.g., −350 to −250 km s −1 ), because at these positive velocities, we see the back side of the Brγ primary wind behind the primary star.…”

Section: Discussionmentioning

confidence: 92%

“…In the Brγ line profile, the outer high-velocity region is dominated by the electron scattering wings (e.g., Hillier et al 2001;Groh et al 2010). However, in the blue line wing, there may also be additional line contributions from (1) fast moving primary wind gas (in the wind cavity) accelerated by the fast secondary wind (Damineli et al 2008a;Groh et al 2010); and (2) the weak He i 2.16127 µm line (the center of this line is approximately at velocity of about −550 km s −1 in the Brγ line profile). Model spectra of η Car computed with the radiative transfer model of Hillier & Miller (1998) and Hillier et al (2001) show that the peak brightness of this He i 2.16127 µm line is about 50 to 100 times weaker than the peak brightness of the Brγ line.…”

Section: High-velocity Structure In the Continuum-subtracted Imagesmentioning

confidence: 99%

“…The cause of the observed ∼1-2 mas (2.35-4.7 au) NW offset of the line images at about −613 to −825 km s −1 is unknown, but the high negative velocity and location of the high-velocity structure suggest that the emitting region (of both the above discussed high-velocity Brγ emission and the He i 2.16127 µm emission) is located in the innermost region of the wind-wind collision cavity (Damineli et al 2008a;Groh et al 2010), because the innermost region of the cavity was in the NW of the center of the continuum image at the phase of our observations (binary separation and PA were 4.9 mas or 11.5 au and 315 • at the time of observation).…”

Section: High-velocity Structure In the Continuum-subtracted Imagesmentioning

confidence: 99%

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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: Discussionmentioning

confidence: 92%

Section: High-velocity Structure In the Continuum-subtracted Imagesmentioning

confidence: 99%

Section: High-velocity Structure In the Continuum-subtracted Imagesmentioning

confidence: 99%

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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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“…2, for details). Variations at many other wavelengths are also coincident with the periastron passage; for example, optical excitation lines undergo a rapid decrease in intensity (Damineli et al 2008a). Although the X-ray emission represents only a tiny fraction of the bolometric luminosity (L X /L bol 10 −7 ), understanding the origin of the hard X-ray emission is crucial, as it is compact and not affected by circumstellar absorption.…”

Section: X-ray Observationsmentioning

confidence: 99%

Hard X-ray identification ofη Carinae and steadiness close to periastron

Leyder¹,

Walter²,

Rauw³

2010

A&A

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Context. The colliding-wind binary η Carinae exhibits soft X-ray thermal emission that varies strongly around the periastron passage. It has been found to have non-thermal emission, thanks to its detection in hard X-rays using INTEGRAL and Suzaku, and also in γ-rays with AGILE and Fermi. Aims. This paper attempts to definitively identify η Carinae as the source of the hard X-ray emission, to examine how changes in the 2-10 keV band influence changes in the hard X-ray band, and to understand more clearly the mechanisms producing the non-thermal emission using new INTEGRAL observations obtained close to periastron passage. Methods. To strengthen the identification of η Carinae with the hard X-ray source, a long Chandra observation encompassing the INTEGRAL/ISGRI error circle was analysed, and all other soft X-ray sources (including the outer shell of η Carinae itself) were discarded as likely counter-parts. To expand the knowledge of the physical processes governing the X-ray lightcurve, new hard X-ray images of η Carinae were studied close to periastron, and compared to previous observations far from periastron. Results. The INTEGRAL component, when represented by a power law (with a photon index Γ of 1.8), would produce more emission in the Chandra band than observed from any point source in the ISGRI error circle apart from η Carinae, as long as the hydrogen column density to the ISGRI source is lower than N H 10 24 cm −2 . Sources with such a high absorption are very rare, thus the hard X-ray emission is very likely to be associated with η Carinae. The eventual contribution of the outer shell to the non-thermal component also remains fairly limited. Close to periastron passage, a 3-σ detection is achieved for the hard X-ray emission of η Carinae, with a flux similar to the average value far from periastron. Conclusions. Assuming a single absorption component for both the thermal and non-thermal sources, this 3-σ detection can be explained with a hydrogen column density that does not exceed N H 6 × 10 23 cm −2 without resorting to an intrinsic increase in the hard X-ray emission. The energy injected in hard X-rays (averaged over a month timescale) appears to be rather constant at least as close as a few stellar radii, well within the acceleration region of the wind.

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“…The effect of the secondary gravity when the secondary approaches the primary on its highly eccentric (e 0.9) orbit is thought to be strongly related to the occasion of the spectroscopic event. During the spectroscopic event many emission and absorption lines and bands show considerable changes for a few weeks (Damineli et al 2008 and references therein), e.g., a deep minimum in the X-ray emission. The X-ray emission, for example, comes from the colliding stellar winds, (Corcoran 2005;Corcoran et al 2010;Parkin et al 2011;Akashi et al 2006Akashi et al , 2011Moffat & Corcoran 2009;Henley et al 2008;Okazaki et al 2008;Pittard & Corcoran 2002Behar et al 2007;Teodoro et al 2012), while its minimum is attributed to the suppression of the secondary wind near periastron passages.…”

Section: Introductionmentioning

confidence: 99%

The interaction of the eta carinae primary wind with a century old slow equatorial ejecta

Soker¹,

Kashi²

2012

New Astronomy

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We argue that the asymmetric morphology of the blue and red shifted components of the outflow at hundreds of AU from the massive binary system η Carinae can be understood from the collision of the primary stellar wind with the slowly expanding dense equatorial gas. Recent high spatial observations of some forbidden lines, e.g. [Fe III] λ4659, reveal the outflowing gas within about one arcsecond (2300 AU) from η Car. The distribution of the blue and red shifted components are not symmetric about the center, and they are quite different from each other. The morphologies of the blue and red shifted components correlate with the location of dense slowly moving equatorial gas (termed the Weigelt blob environment; WBE), that is thought to have been ejected during the 1887 -1895 Lesser Eruption (LE). In our model the division to the blue and red shifted components is caused by the postshock flow of the primary wind on the two sides of the equatorial plane after it collides with the WBE. The fast wind from the secondary star plays no role in our model for these components, and it is the freely expanding primary wind that collides with the WBE. Because the line of sight is inclined to the binary axis, the two components are not symmetric. We show that the postshock gas can also account for the observed intensity in the [Fe III] λ4659 line.

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A multispectral view of the periodic events in η Carinae

Cited by 78 publications

References 48 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

Hard X-ray identification ofη Carinae and steadiness close to periastron

The interaction of the eta carinae primary wind with a century old slow equatorial ejecta

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