The H-alpha Variations of eta Carinae During the 2009.0 Spectroscopic Event

TL;DR

This study presents detailed H-alpha spectral observations of eta Carinae during its 2009 spectroscopic event, revealing line profile changes linked to stellar wind interactions and binary dynamics.

Contribution

It provides new high-cadence spectroscopic data during the 2009 event, showing specific line profile variations associated with wind-wind collision effects.

Findings

H-alpha emission faded significantly after the X-ray minimum.

Broad P Cygni absorption appeared prior to flux minimum.

Features are consistent with wind collision and atmospheric eclipse models.

Abstract

We report on H-alpha spectroscopy of the 2009.0 spectroscopic event of eta Carinae collected via SMARTS observations using the CTIO 1.5 m telescope and echelle spectrograph. Our observations were made almost every night over a two month interval around the predicted minimum of eta Car. We observed a significant fading of the line emission that reached a minimum seven days after the X-ray minimum. About 17 d prior to the H-alpha flux minimum, the H-alpha profile exhibited the emergence of a broad, P Cygni type, absorption component (near a Doppler shift of -500 km/s) and a narrow absorption component (near -144 km/s and probably associated with intervening gas from the Little Homunculus Nebula). All these features were observed during the last event in 2003.5 and are probably related to the close periastron passage of the companion. We argue that these variations are consistent with qualitative expectations about changes in the primary star's stellar wind that result from the wind-wind collision with a massive binary companion and from atmospheric eclipses of the companion.