Eta Carinae's 2014.6 Spectroscopic Event: The Extraordinary He II and N II Features

TL;DR

This study examines the 2014 spectroscopic event of Eta Carinae, highlighting significant increases in He II and N II features that suggest a decline in wind density and changes in the ionizing radiation environment.

Contribution

It provides new observational evidence of spectral feature variations during Eta Carinae's 2014 event, supporting models of evolving stellar wind and accretion processes.

Findings

Significant increase in He II 4687 and N II features in 2014 compared to 2009.

Results consistent with a decline in primary wind density over time.

Possible reduction in accretion rate onto the companion star near periastron.

Abstract

Eta Carinae's spectroscopic events (periastron passages) in 2003, 2009, and 2014 differed progressively. He II 4687 and nearby N II multiplet 5 have special significance because they respond to very soft X-rays and the ionizing UV radiation field (EUV). HST/STIS observations in 2014 show dramatic increases in both features compared to the previous 2009.1 event. These results appear very consistent with a progressive decline in the primary wind density, proposed years ago on other grounds. If material falls onto the companion star near periastron, the accretion rate may now have become too low to suppress the EUV