To $v_{\infty }$ and beyond! The He I absorption variability across the 2014.6 periastron passage of $\eta$ Carinae

Abstract

We have monitored the massive binary star $\eta$ Carinae with the CTIO/SMARTS 1.5~m telescope and CHIRON spectrograph from the previous apastron passage of the system through the recent 2014.6 periastron passage. Our monitoring has resulted in a large, homogeneous data set with an unprecedented time-sampling, spectral resolving power, and signal-to-noise. This allowed us to investigate temporal variability previously unexplored in the system and discover a kinematic structure in the P Cygni absorption troughs of neutral helium wind lines. The features observed occurred prior to the periastron passage and are seen as we look through the trailing arm of the wind-wind collision shock cone. We show that the bulk of the variability is repeatable across the last five periastron passages, and that the absorption occurs in the inner 230 AU of the system. In addition, we found an additional, high-velocity absorption component super-imposed on the P Cygni absorption troughs that has been previously un-observed in these lines, but which bears resemblance to the observations of the He~I $\lambda$10830 Å feature across previous cycles. Through a comparison of the current smoothed particle hydrodynamical simulations, we show that the observed variations are likely caused by instabilities in the wind-wind collision region in our line-of-sight, coupled with stochastic variability related to clumping in the winds.

accepted to MNRAS, 28 pages including 14 figures and a 9 page appendix

References in corpus (13)

• Binary interaction dominates the evolution of massive stars
• Southern Massive Stars at High Angular Resolution: Observational Campaign and Companion Detection
• Near-Infrared interferometry of Eta Carinae with high spatial and spectral resolution using the VLTI and the AMBER instrument
• Chemical evolution of galaxies. I. A composition-dependent SPH model for chemical evolution and cooling
• The UV Scattering Halo of the Central Source Associated with Eta Carinae
• A multispectral view of the periodic events in eta Carinae
• The Early Spectra of Eta Carinae 1892 to 1941 and the Onset of Its High Excitation Emission Spectrum
• He II $\lambda$4686 emission from the massive binary system in $\eta$ Car: constraints to the orbital elements and the nature of the periodic minima
• 3D radiative transfer simulations of Eta Carinae's inner colliding winds - I. Ionization structure of helium at apastron
• The Eta Carinae optical 2009.0 event, a new "eclipse-like" phenomenon
• Eta Carinae's 2014.6 Spectroscopic Event: The Extraordinary He II and N II Features
• 3D Printing Meets Computational Astrophysics: Deciphering the Structure of Eta Carinae's Inner Colliding Winds
• 3D Radiative Transfer in $\eta$ Carinae: Application of the SimpleX Algorithm to 3D SPH Simulations of Binary Colliding Winds

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