Explaining the transient fast blue absorption lines in the massive binary system η Carinae

Kashi, Amit; Soker, Noam; Akashi, Muhammad

doi:10.1111/j.1365-2966.2011.18340.x

Cited by 5 publications

(2 citation statements)

References 46 publications

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“…The observed equivalent width and radial velocity variations of the wind lines can only be matched if the illuminated hemisphere of the primary is partially directed away from us at periastron toward a more distant companion. Thus, earlier suggestions that the companion is in the foreground at periastron (Kashi et al 2011) are no longer tenable.…”

Section: Discussionmentioning

confidence: 99%

THE OPTICAL WIND LINE VARIABILITY OFηCARINAE DURING THE 2009.0 EVENT

Richardson

Gies

Gull

et al. 2015

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We report on high-resolution spectroscopy of the 2009.0 spectroscopic event of η Carinae collected via SMARTS observations using the CTIO 1.5 m telescope and echelle spectrograph. Our observations were made almost every night over a two-month interval around the photometric minimum of η Car associated with the periastron passage of a hot companion. The photoionizing flux of the companion and heating related to colliding winds causes large changes in the wind properties of the massive primary star. Here we present an analysis of temporal variations in a sample of spectral lines that are clearly formed in the wind of the primary star. These lines are affected by a changing illumination of the flux of the secondary star during the periastron passage. We document the sudden onset of blueshifted absorption that occurred in most of the lines near or slightly after periastron, and we argue that these absorption components are seen when we view the relatively undisturbed wind of the foreground primary star. We present time series measurements of the net equivalent width of the wind lines and of the radial velocities of the absorption trough minima and the emission peak midpoints. Most lines decrease in emission strength around periastron, and those high excitation lines formed close to the primary exhibit a red-ward velocity excursion. We show how these trends can be explained using an illuminated hemisphere model that is based on the idea that the emission originates primarily from the side of the primary facing the hot companion.

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Section: Discussionmentioning

confidence: 99%

THE OPTICAL WIND LINE VARIABILITY OFηCARINAE DURING THE 2009.0 EVENT

Richardson

Gies

Gull

et al. 2015

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“…first isOkazaki et al (2008),Parkin et al (2009),Parkin et al (2011,Russell (2013),Hamaguchi et al (2014),Clementel et al (2015a),and Clementel et al (2015b), while the second is supported bySoker & Behar (2006),Kashi & Soker (2008),Kashi & Soker (2009), Falceta-Gonçalves & Abraham (2009),Abraham & Falceta- Gonçalves (2010), andKashi et al (2011). The most constraining work for determining the line of sight to η Carinae isMadura et al (2012) since, as opposed to the pointsource nature of the other diagnostics, they used spatially resolved [Fe] emission to constrain all three viewing anglesinclination, azimuth, and position angle (PA) -to i ∼ 135 • , ω ∼ 252 • , and PA ∼ 40 • , which aligns the orbital axis with the Homunculus axis.…”

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confidence: 84%

Modelling the Central Constant Emission X-ray component of η Carinae

Russell

Corcoran

Hamaguchi

et al. 2016

Mon. Not. R. Astron. Soc.

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The X-ray emission of η Carinae shows multiple features at various spatial and temporal scales. The central constant emission (CCE) component is centred on the binary and arises from spatial scales much smaller than the bipolar Homunculus nebula, but likely larger than the central wind-wind collision region between the stars as it does not vary over the ∼2-3 month X-ray minimum when it can be observed. Using large-scale 3D smoothed particle hydrodynamics (SPH) simulations, we model both the colliding-wind region between the stars, and the region where the secondary wind collides with primary wind ejected from the previous periastron passage. The simulations extend out to one hundred semimajor axes and make two limiting assumptions (strong coupling and no coupling) about the influence of the primary radiation field on the secondary wind. We perform 3D radiative transfer calculations on the SPH output to synthesize the X-ray emission, with the aim of reproducing the CCE spectrum. For the preferred primary mass-loss rateṀ A ≈ 8.5 × 10 −4 M yr −1 , the model spectra well reproduce the observation as the strong-and no-coupling spectra bound the CCE observation for longitude of periastron ω ≈ 252 • , and bound/converge on the observation for ω ≈ 90 • . This suggests that η Carinae has moderate coupling between the primary radiation and secondary wind, that both the region between the stars and the comoving collision on the backside of the secondary generate the CCE, and that the CCE cannot place constraints on the binary's line of sight. We also discuss comparisons with common X-ray fitting parameters.

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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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Explaining the transient fast blue absorption lines in the massive binary system η Carinae

Cited by 5 publications

References 46 publications

THE OPTICAL WIND LINE VARIABILITY OFηCARINAE DURING THE 2009.0 EVENT

THE OPTICAL WIND LINE VARIABILITY OFηCARINAE DURING THE 2009.0 EVENT

Modelling the Central Constant Emission X-ray component of η Carinae

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

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