The N II Lines in Eta Carinae: A Further Evidence for Mass Transfer During the Nineteenth Century Great Eruption

TL;DR

This paper presents evidence that N II lines observed in Eta Carinae originate from the secondary star's wind, supporting the hypothesis of historical mass transfer during the Great Eruption and providing insights into the system's binary orientation.

Contribution

It offers new evidence linking N II lines to the secondary's wind, supporting mass transfer history and clarifying the binary orientation in Eta Carinae.

Findings

N II lines originate in the secondary's wind acceleration zone.

The lines' Doppler shifts match between emission and absorption components.

Supports the binary model with the secondary closer to us near periastron.

Abstract

We argue that the emission and the absorption components of he N II lines recently observed in Eta Carinae can originate in the secondary's wind acceleration zone. We base this claim in part on the presence of these lines in hot nitrogen rich stars, such as WN 8 stars, and on the expected clumpy nature of such winds. The envelope of the secondary star in Eta Carinae is expected to be nitrogen rich due to accretion of few solar masses of the primary luminous blue variable's nitrogen rich material during the nineteenth century Great Eruption. Another argument in support of N II lines origin in the acceleration zone of the secondary wind is the behavior of the emission components. The emission components of the lines show the same Doppler shift variation as that of the absorption components. The secondary's-wind origin of the N II lines is compatible with the binary orientation in which the secondary is closer to us near periastron passage.