HST/FOS spectroscopy of ETA Carinae: the star itself, and ejecta within 0.3 arcsec

Davidson, Kris; Ebbets, Dennis; Weigelt, G.; Humphreys, R. M.; Hajian, Arsen R.; Walborn, N. R.; Rosa, M. R.

doi:10.1086/117408

Cited by 110 publications

(181 citation statements)

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“…Using their Ñuxes for the IR lines together with the value of D7 ] 10~13 ergs cm~2 s~1 observed for Fe II j1870 by Feibelman et al (1991), indicates that j1870 is less than 5% of the value expected from the strength of the 1 km Fe II features if Lya Ñuorescence was the principal excitation mechanism. Fe II j9997 is also seen in g Car (Hamann et al 1994), but j1870 is not apparent in the UV spectrum of Davidson et al (1995).…”

Section: Excitation Mechanismmentioning

confidence: 96%

The 1 Micron FeiiLines of the Seyfert Galaxy I Zw 1

Rudy

Mazuk

Puetter

et al. 2000

ApJ

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Infrared spectrophotometric observations from 0.8 to 2.5 km are presented for the narrow-line, type 1 Seyfert galaxy I Zw 1. The data clearly reveal Fe II j9997, j10501, j10863, and j11126Èthe so-called "" 1 km Fe II lines.ÏÏ These features are by far the strongest Fe II transitions in the entire 0.8È2.5 km spectral region and, relative to the hydrogen lines, are equal or stronger in I Zw 1 than in any of the Galactic sources in which they have been detected previously. The 1 km Fe II lines, which share a common upper term, are probably emitted by the broad line regions of many active galaxies but have escaped identiÐca-tion because of blending with nearby features of hydrogen and helium. A mechanism for their excitation through Ñuorescence by Lya has been suggested previously in the literature, but the crucial cascade lines that feed the upper term in this process are not seen in I Zw 1. The low energy of the upper term indicates that the 1 km Fe II lines are collisionally excited.

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Section: Excitation Mechanismmentioning

confidence: 96%

The 1 Micron FeiiLines of the Seyfert Galaxy I Zw 1

Rudy

Mazuk

Puetter

et al. 2000

ApJ

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“…This seems to be puzzling because the objects B, C, and D are objects illuminated by the central object (and only a very small fraction of the star flux hits these objects). Therefore, several authors suggested that disk-like or toroidal occulting material in our line-of-sight to the central object may partially obscure the central star, but not the objects B, C, and D, just like a natural coronagraph (Hillier & Allen 1992;Weigelt et al 1995;Davidson et al 1995Hillier et al 2001;Smith et al 2002Smith et al , 2004Mehner et al 2010a;Madura et al 2013).…”

Section: Toroidal Occulting Gas and Dust In The Line-of-sight To The mentioning

confidence: 98%

“…These dots are caused by the emission region that produces the well-known narrow emission line component at about −40 km s −1 . This narrow emission line component in the Brγ line of η Car is caused by the ejected, slow-moving objects B, C, and D (Weigelt & Ebersberger 1986;Hofmann & Weigelt 1988;Davidson et al 1995 at separations from 0.1 to 0.3 (see Sect. 4).…”

Section: Appendix A: Image Reconstructionmentioning

confidence: 99%

“…These structures are called fossil wind structures, because they were created over several orbital cycles in the past. Various observations suggest that disk-like or toroidal material in our line-of-sight to the central object partially obscures the central star (e.g., Hillier & Allen 1992;Weigelt et al 1995;Davidson et al 1995Hillier et al 2001;Smith et al 2002Smith et al , 2004Mehner et al 2010a;Madura et al 2013). To study this occulting material, Falcke et al (1996) performed speckle masking imaging polarimetry (in Hα plus continuum).…”

Section: Introductionmentioning

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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“…The near-IR radiation arises from more than one component, but is likely dominated by free-free emission from the stellar wind (Whitelock et al 2004, Whitelock 2005. Other sources include scattered light from the Homunculus and from close ejecta like the Weigelt knots (Weigelt & Ebersberger 1986, Davidson et al 1995, Weigelt & Kraus 2012, emission lines (<10%, mostly H I and He I), and at K and L band hot circumstellar dust (T dust ≫ 200 K) contributes. Conceivably all components play a role but the importance of each source is still debated.…”

Section: Introductionmentioning

confidence: 99%

Near-infrared evidence for a sudden temperature increase in Eta Carinae

Mehner¹,

Ishibashi²,

Whitelock³

et al. 2014

A&A

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Aims. Eta Car's ultra-violet, optical, and X-ray light curves and its spectrum suggest a physical change in its stellar wind over the last decade. It was proposed that the mass-loss rate decreased by a factor of about 2 in the last 15 years. We complement these recent results by investigating the past evolution and the current state of η Car in the near-infrared (IR). Results. The long-term brightening trends in η Car's JHKL light curves were discontinuous around the 1998 periastron passage. After 1998, the star shows excess emission above the extrapolated trend from earlier dates, foremost in J and H, and the blueward, cyclical progression in its near-IR colors is accelerated. The near-IR color evolution is strongly correlated with the periastron passages. After correcting for the secular trend we find that the color evolution matches an apparent increase in blackbody temperature of an optically thick near-IR emitting plasma component from about 3500 to 6000 K over the last 20 years. Conclusions. We suggest that the changing near-IR emission may be caused by variability in optically thick bremsstrahlung emission. Periastron passages play a key role in the observed excess near-IR emission after 1998 and the long-term color evolution. We thus propose as a hypothesis that angular momentum transfer (via tidal acceleration) during periastron passages leads to sudden changes in η Car's atmosphere resulting in a long-term decrease in the mass-loss rate.

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HST/FOS spectroscopy of ETA Carinae: the star itself, and ejecta within 0.3 arcsec

Cited by 110 publications

References 0 publications

The 1 Micron FeiiLines of the Seyfert Galaxy I Zw 1

The 1 Micron FeiiLines of the Seyfert Galaxy I Zw 1

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

Near-infrared evidence for a sudden temperature increase in Eta Carinae

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