Mass and Kinetic Energy of the Homunculus Nebula around η Carinae

Smith, Nathan; Gehrz, R. D.; Hinz, Philip M.; Hoffmann, W. F.; Hora, J. L.; Mamajek, Eric E.; Meyer, Michael

doi:10.1086/346278

Cited by 257 publications

(457 citation statements)

References 27 publications

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“…However, although NaSt1 shares some interesting similarities with η Car's Homunculus, the new data highlight some obvious differences, described as follows. The Homunculus was created during an extremely energetic explosion that ejected at least ≈ 12 M⊙ of material at velocities of ≈ 600 km s −1 (a ∼ 10 50 erg event; Smith et al 2003). The outflow exhibits a striking bipolar morphology and is a strong source of [N ii] emission, but also Hα and strong optical-infrared continuum from scattered light and thermal radiation from dust.…”

Section: Discussionmentioning

confidence: 99%

Multiwavelength observations of NaSt1 (WR 122): equatorial mass loss and X-rays from an interacting Wolf–Rayet binary

Mauerhan

Smith

Dyk

et al. 2015

Monthly Notices of the Royal Astronomical Society

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NaSt1 (aka Wolf-Rayet 122) is a peculiar emission-line star embedded in an extended nebula of [N ii] emission with a compact dusty core. This object was characterized by Crowther & Smith (1999) as a Wolf-Rayet (WR) star cloaked in an opaque nebula of CNO-processed material, perhaps analogous to η Car and its Homunculus nebula, albeit with a hotter central source. To discern the morphology of the [N ii] nebula we performed narrowband imaging using the Hubble Space Telescope and Wide-field Camera 3. The images reveal that the nebula has a disk-like geometry tilted ≈12 • from edge-on, composed of a bright central ellipsoid surrounded by a larger clumpy ring. Ground-based spectroscopy reveals radial velocity structure (±10 km s −1 ) near the outer portions of the nebula's major axis, which is likely to be the imprint of outflowing gas. Near-infrared adaptive-optics imaging with Magellan AO has resolved a compact ellipsoid of K s -band emission aligned with the larger [N ii] nebula, which we suspect is the result of scattered He i line emission (λ2.06 µm). Observations with the Chandra X-ray Observatory have revealed an X-ray point source at the core of the nebula that is heavily absorbed at energies < 1 keV and has properties consistent with WR stars and colliding-wind binaries. We suggest that NaSt1 is a WR binary embedded in an equatorial outflow that formed as the result of non-conservative mass transfer. NaSt1 thus appears to be a rare and important example of a stripped-envelope WR forming through binary interaction, caught in the brief Roche-lobe overflow phase.

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Section: Discussionmentioning

confidence: 99%

Multiwavelength observations of NaSt1 (WR 122): equatorial mass loss and X-rays from an interacting Wolf–Rayet binary

Mauerhan

Smith

Dyk

et al. 2015

Monthly Notices of the Royal Astronomical Society

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“…AFGL 2298 et al However, Smith et al (2003) found that only 10−20% (≤2.5 M ) of the total mass of the Homunculus is located in the equatorial region, whereas the masses of the nebulae in question are ∼8.9−11 M . Thus, at the very least it would appear that the latitudinal distribution of nebular mass would have to differ between these objects; applying the "equatorial" to "polar" mass ratio found for the Homunculus to AFGL 2298, AG Car and the Pistol Star would imply total nebular masses in excess of ∼50 M .…”

Section: Outbursts and Nebular Formationmentioning

confidence: 99%

Bolometric luminosity variations in the luminous blue variable AFGL2298

Clark¹,

Crowther

Larionov

et al. 2009

A&A

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Aims. We characterise the variability in the physical properties of the luminous blue variable AFGL 2298 (IRAS 18576+0341) between 1989−2008. Methods. In conjunction with published data from 1989−2001, we have undertaken a long term (2001−2008) near-IR spectroscopic and photometric observational campaign for this star and utilise a non-LTE model atmosphere code to interpret these data. Results. We find AFGL 2298 to have been highly variable during the two decades covered by the observational datasets. Photometric variations of ≥1.6 mag have been observed in the JHK wavebands; however, these are not accompanied by correlated changes in near-IR colour. Non-LTE model atmosphere analysis of 4 epochs of K band spectroscopy obtained between 2001−7 suggests that the photometric changes of AFGL 2298 were driven by expansion and contraction of the stellar photosphere accompanied by comparatively small changes in the stellar temperature (ΔT * ∼ 4.5 kK). Unclumped mass loss rates throughout this period were modest and directly comparable to those of other highly luminous (candidate) LBVs. However, the main finding of this analysis was that the bolometric luminosity of AFGL 2298 appears to have varied by at least a factor of ∼2 between 1989−2008, with it being one of the most luminous stars in the Galaxy during maximum. Comparison to other LBVs that have undergone non bolometric luminosity conserving "eruptions" shows such events to be heterogeneous, with AFGL 2298 the least extreme example. These results -and the diverse nature of both the quiescent LBVs and associated ejecta -may offer support to the suggestion that more than one physical mechanism is responsible for such behaviour.

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“…The famous bipolar Homunculus Nebula is thought to be the result of the "Great Eruption" in the 1840's (see Smith et al 1998;Currie & Dowling 1999;Morse et al 2001;Smith 2005;Artigau et al 2011;Davidson & Humphreys 2012). The total dust + gas mass in the bipolar nebula and a dense equatorial torus in the Homunculus is estimated to be about 15−20 M (Morris et al 1999;Smith et al 2003). The angular diameter of the optically bright parts of the Homunculus Nebula as seen in the HST images is 18 × 11 (long axis × short axis).…”

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

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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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Mass and Kinetic Energy of the Homunculus Nebula around η Carinae

Cited by 257 publications

References 27 publications

Multiwavelength observations of NaSt1 (WR 122): equatorial mass loss and X-rays from an interacting Wolf–Rayet binary

Multiwavelength observations of NaSt1 (WR 122): equatorial mass loss and X-rays from an interacting Wolf–Rayet binary

Bolometric luminosity variations in the luminous blue variable AFGL2298

Herschelfar-infrared observations of the Carina Nebula complex

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