The Hα variations of η Carinae during the 2009.0 spectroscopic event

Abstract

We report on Hα spectroscopy of the 2009.0 spectroscopic event of η Carinae collected via SMARTS observations using the Cerro Tololo Interamerican Observatory 1.5 m telescope and echelle spectrograph. Our observations were made almost every night over a two-month interval around the predicted minimum of η Car. We observed a significant fading of the line emission that reached a minimum 7 days after the X-ray minimum. About 17 days prior to the Hα flux minimum, the Hα profile exhibited the emergence of a broad, P Cygni type, absorption component (near a Doppler shift of -500 km s<SUP>-1</SUP>) and a narrow absorption component (near -144 km s<SUP>-1</SUP> 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.