A blast wave from the 1843 eruption of η Carinae

Abstract

Very massive stars shed much of their mass in violent precursor eruptions1 as luminous blue variables2 (LBVs) before reaching their most likely end as supernovae, but the cause of LBV eruptions is unknown. The nineteenth-century eruption of η Carinae, the prototype of these events3, ejected about 12 solar masses at speeds of 650 km s-1, with a kinetic energy of almost 1050 erg (ref. 4). Some faster material with speeds up to 1,000–2,000 km s-1 had previously been reported5,6,7,8 but its full distribution was unknown. Here I report observations of much faster material with speeds up to 3,500–6,000 km s-1, reaching farther from the star than the fastest material in previous reports5. This fast material roughly doubles the kinetic energy of the nineteenth-century event and suggests that it released a blast wave now propagating ahead of the massive ejecta. As a result, η Carinae’s outer shell now mimics a low-energy supernova remnant. The eruption has usually been discussed in terms of an extreme wind driven by the star’s luminosity2,3,9,10, but the fast material reported here indicates that it may have been powered by a deep-seated explosion rivalling a supernova, perhaps triggered by the pulsational pair instability11. This may alter interpretations of similar events seen in other galaxies.

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Figure 1: Example of the velocity structures seen in the He i λ10830 line.
Figure 2: Extremely fast nitrogen-rich material surrounding η Carinae.
Figure 3: Illustration of the possible geometry of η Carinae’s blast wave.

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Acknowledgements

I acknowledge continuing collaboration and relevant discussions with the supernova group at the University of California at Berkeley.

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Correspondence to Nathan Smith.

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Smith, N. A blast wave from the 1843 eruption of η Carinae. Nature 455, 201–203 (2008). https://doi.org/10.1038/nature07269

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