The Company Eta Carinae Keeps: Stellar and Interstellar Content of the Carina Nebula

Eta Carinae, the closest, active, massive binary containing a highly unstable LBV, exhibits expanding, compressed wind shells, seen in emission, that are spatially and spectrally resolved by HST/STIS. Starting in June 2009, these structures were mapped across its 5.54-year, highly elliptical, binary orbit to follow temporal changes in the light of [Fe III] Multiple fossil wind-structures were traced across the 5.7-year monitoring interval. The strong similarity of the expanding [Fe II] shells suggests that the wind and photo-ionization properties of the massive binary have not changed substantially from one orbit to the next over the past several orbital cycles. These observations trace structures that can be used to test three-dimensional hydrodynamical and radiative-transfer models of massive, interacting winds. They also provide a baseline for following future changes in η Car, especially of its winds and photoionization properties.

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“…For the convenience of the reader, η Car is at a distance of 2300 pc (Walborn 2012). An angular dimension of 0.…”

Section: Structural Changes With Orbital Phasementioning

confidence: 99%

The fossil wind structures of Eta Carinae: changes across one 5.54-yr cycle

Gull

Madura

Teodoro

et al. 2016

Mon. Not. R. Astron. Soc.

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Simulating the formation of η Carinae’s surrounding nebula through unstable triple evolution and stellar merger-induced eruption

Hirai

Podsiadlowski

Owocki

et al. 2021

Monthly Notices of the Royal Astronomical Society

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η Carinae is an extraordinary massive star famous for its 19th century Great Eruption and the surrounding Homunculus nebula ejected in that event. The cause of this eruption has been the centre of a long-standing mystery. Recent observations, including light-echo spectra of the eruption, suggest that it most likely resulted from a stellar merger in an unstable triple system. Here we present a detailed set of theoretical calculations for this scenario, from the dynamics of unstable triple systems and the mass ejection from close binary encounters, to the mass outflow from the eruption caused by the stellar merger and the post-merger wind phase. In our model the bipolar post-merger wind is the primary agent for creating the Homunculus, as it sweeps up external eruption ejecta into a thin shell. Our simulations reproduce many of the key aspects of the shape and kinematics of both the Homunculus nebula and its complex surrounding structure, providing strong support for the merger-in-a-triple scenario.

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The spectacular evolution of Supernova 1996al over 15 yr: a low-energy explosion of a stripped massive star in a highly structured environment

Benetti

Чугай

Utrobin

et al. 2016

Mon. Not. R. Astron. Soc.

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Spectrophotometry of SN 1996al carried out throughout 15 years is presented. The early photometry suggests that SN 1996al is a Linear type-II supernova, with an absolute peak of M V ∼ −18.2 mag. Early spectra present broad, asymmetric Balmer emissions, with super-imposed narrow lines with P-Cygni profile, and He I features with asymmetric, broad emission components. The analysis of the line profiles shows that the H and He broad components form in the same region of the ejecta. By day +142, the Hα profile dramatically changes: the narrow P-Cygni profile disappears, and the Hα is fitted by three emission components, that will be detected over the remaining 15 yrs of the SN monitoring campaign. Instead, the He I emissions become progressively narrower and symmetric. A sudden increase in flux of all He I lines is observed between 300 and 600 days. Models show that the supernova luminosity is sustained by the interaction of low mass (∼ 1.15 M ) ejecta, expelled in a low kinetic energy (∼ 1.6×10 50 erg) explosion, with highly asymmetric circumstellar medium. The detection of Hα emission in pre-explosion archive images suggests that the progenitor was most likely a massive star (∼ 25 M ZAMS) that had lost a large fraction of its hydrogen envelope before explosion, and was hence embedded in a H-rich cocoon. The low-mass ejecta and modest kinetic energy of the explosion are explained with massive fallback of material into the compact remnant, a 7 − 8 M black hole.

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The Company Eta Carinae Keeps: Stellar and Interstellar Content of the Carina Nebula

Cited by 6 publications

References 67 publications

The fossil wind structures of Eta Carinae: changes across one 5.54-yr cycle

The fossil wind structures of Eta Carinae: changes across one 5.54-yr cycle

Simulating the formation of η Carinae’s surrounding nebula through unstable triple evolution and stellar merger-induced eruption

The spectacular evolution of Supernova 1996al over 15 yr: a low-energy explosion of a stripped massive star in a highly structured environment

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