A Blast Wave from the 1843 Eruption of Eta Carinae

TL;DR

This study reveals that Eta Carinae's 19th-century eruption included extremely fast ejecta, indicating a deep-seated explosion akin to a supernova, which challenges previous wind-driven eruption models and impacts understanding of similar stellar events.

Contribution

It provides the first detailed observations of ejecta moving at 3500-6000 km/s from Eta Carinae's eruption, suggesting a supernova-like explosion rather than a wind-driven event.

Findings

Fast ejecta up to 6000 km/s were observed.

The eruption's kinetic energy roughly doubled due to this fast material.

The event likely involved a deep-seated explosion similar to a supernova.

Abstract

Very massive stars shed much of their mass in violent precursor eruptions as luminous blue variables (LBVs) before reaching their most likely end as supernovae, but the cause of LBV eruptions is unknown. The 19th century eruption of Eta Carinae, the prototype of these events, ejected about 12 solar masses at speeds of 650 km/s, with a kinetic energy of almost 10^50 ergs. Some faster material with speeds up to 1000-2000 km/s had previously been reported but its full distribution was unknown. Here I report observations of much faster material with speeds up to 3500-6000 km/s, reaching farther from the star than the fastest material in earlier reports. This fast material roughly doubles the kinetic energy of the 19th century event, and suggests that it released a blast wave now propagating ahead of the massive ejecta. Thus, Eta Car'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 luminosity, but fast material reported here suggests that it was powered by a deep-seated explosion rivalling a supernova, perhaps triggered by the pulsational pair instability. This may alter interpretations of similar events seen in other galaxies.