Submillimetre variability of Eta Carinae: cool dust within the outer ejecta

Gomez, Haley Louise; Vlahakis, C.; Stretch, Catherine Mary; Dunne, L.; Eales, Stephen Anthony; Beelen, A.; Gomez, Edward; Edmunds, M. G.

doi:10.1111/j.1745-3933.2009.00784.x

Cited by 54 publications

(66 citation statements)

References 32 publications

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“…They argue that the expansion of the Homunculus can only account for a 20% drop in the far-IR radiation and propose dynamical changes in the circumstellar dust around η Car. However, Gomez et al (2010) found that the flux at 870 µm, a wavelength region dominated by free-free emission from the ionized wind, was a factor of 3 higher in 2007 compared to 1998, which can be primarily accounted for by the cyclical 5.5 yr variations. Radio monitoring by White (priv.…”

Section: Discussionmentioning

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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Section: Discussionmentioning

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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“…In the optical band, the brightness of η Car increased by several magnitudes during the last ∼30 years (see Fernández-Lajús et al 2009;Gomez et al 2010;Smith & Frew 2011). This increasing optical brightness suggests that the inner envelope, that enshrouds the central star, is currently opening up (Martin et al 2006), and a larger fraction of the stellar optical and UV radiation, that was previously absorbed within the nebula and thus heated the dust, is now able to leave the system.…”

Section: The Far-infrared Spectral Energy Distribution Of η Carinaementioning

confidence: 99%

Herschelfar-infrared observations of the Carina Nebula complex

Gaczkowski

Preibisch

Ratzka

et al. 2012

A&A

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Context. The Carina Nebula represents one of the largest and most active star forming regions known in our Galaxy. It contains numerous very massive (M > ∼ 40 M ) stars that strongly affect the surrounding clouds by their ionizing radiation and stellar winds. Aims. Our recently obtained Herschel PACS and SPIRE far-infrared maps cover the full area (≈8.7 deg 2 ) of the Carina Nebula complex (CNC) and reveal the population of deeply embedded young stellar objects (YSOs), most of which are not yet visible in the mid-or near-infrared. Methods. We study the properties of the 642 objects that are independently detected as point-like sources in at least two of the five Herschel bands. For those objects that can be identified with apparently single Spitzer counterparts, we use radiative transfer models to derive information about the basic stellar and circumstellar parameters. Results. We find that about 75% of the Herschel-detected YSOs are Class 0 protostars. The luminosities of the Herschel-detected YSOs with SED fits are restricted to values of ≤5400 L , their masses (estimated from the radiative transfer modeling) range from ≈1 M to ≈10 M . Taking the observational limits into account and extrapolating the observed number of Herschel-detected protostars over the stellar initial mass function suggest that the star formation rate of the CNC is ∼0.017 M /year. The spatial distribution of the Herschel YSO candidates is highly inhomogeneous and does not follow the distribution of cloud mass. Rather, most Herschel YSO candidates are found at the irradiated edges of clouds and pillars. The far-infrared fluxes of the famous object η Car are about a factor of two lower than expected from observations with the Infrared Space Observatory obtained 15 years ago; this difference may be a consequence of dynamical changes in the circumstellar dust in the Homunculus Nebula around η Car. Conclusions. The currently ongoing star formation process forms only low-mass and intermediate-mass stars, but no massive (M > ∼ 20 M ) stars. The characteristic spatial configuration of the YSOs provides support to the picture that the formation of this latest stellar generation is triggered by the advancing ionization fronts.

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“…On the other hand, these models also show that the effectiveness of dust destruction depends on various properties such as the geometry of the shocks, the density of the ejecta and the ISM, the size and shape of the grains, clumping in the SNe ejecta, and different SN types. In addition there is some observational evidence that type IIn SNe and sources such as luminous blue variables are possibly efficient dust producers (Fox et al 2009;Smith et al 2009;Gomez et al 2010). While dust production and destruction in SNe is yet unresolved, a "maximum" SN efficiency cannot be ruled out (e.g., Gall et al in prep).…”

Section: Sn Efficiency and Mass Of The Galaxymentioning

confidence: 99%

Genesis and evolution of dust in galaxies in the early Universe

Gall

Andersen

Hjorth

2011

A&A

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Aims. We intend to assess the most plausible scenarios for generating large amounts of dust in high-z quasars (QSOs) on the basis of observationally derived physical properties of QSOs at z 6. Methods. We use a chemical evolution model to compute the temporal progression of quantities such as the amount of dust and gas, stellar masses, star formation rates (SFRs) and the metallicity for various combinations of the initial mass function (IMF), the mass of the galaxy, dust production efficiencies, and the degree of dust destruction in the ISM. We investigate the influence of the SFR on the evolution of these quantities, and determine the earliest epochs at which agreement with observations can be achieved. We apply the obtained results to individual QSOs at z 6. Results. We find that large quantities of dust can be generated rapidly as early as 30 Myr after the onset of the starburst when the SFR of the starburst is 10 3 M yr −1 . The amount of dust and several other physical quantities of individual QSOs at z 6 are satisfactorily reproduced by models at epochs 30, 70, 100, and 170 Myr for galaxies with initial gas masses of 1-3 × 10 11 M . The best agreement with observations is obtained with top-heavy IMFs. A sizable dust contribution from supernovae (SNe) is however required, while at these epochs dust production by asymptotic giant branch (AGB) stars is negligible. Moderate dust destruction in the ISM can be accommodated.

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Submillimetre variability of Eta Carinae: cool dust within the outer ejecta

Cited by 54 publications

References 32 publications

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

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

Herschelfar-infrared observations of the Carina Nebula complex

Genesis and evolution of dust in galaxies in the early Universe

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