The UV Scattering Halo of the Central Source Associated with Eta Carinae

Abstract

We have made an extensive study of the UV spectrum of Eta Carinae, and find that we do not directly observe the star and its wind in the UV. Because of dust along our line of sight, the UV light that we observe arises from bound-bound scattering at large impact parameters. We obtain a reasonable fit to the UV spectrum by using only the flux that originates outside 0.033". This explains why we can still observe the primary star in the UV despite the large optical extinction -- it is due to the presence of an intrinsic coronagraph in the Eta Carinae system, and to the extension of the UV emitting region. It is not due to peculiar dust properties alone. We have computed the spectrum of the purported companion star, and show that it could only be directly detected in the UV spectrum preferentially in the Far Ultraviolet Spectroscopic Explorer (FUSE) spectral region (912-1175 Ang.). However, we find no direct evidence for a companion star, with the properties indicated by X-ray studies and studies of the Weigelt blobs, in UV spectra. This might be due to reprocessing of the companion's light by the dense stellar wind of the primary. Broad FeII and [FeII] emission lines, which form in the stellar wind, are detected in spectra taken in the SE lobe, 0.2" from the central star. The wind spectrum shows some similarities to the spectra of the B & D Weigelt blobs, but also shows some marked differences in that high excitation lines, and lines pumped by Ly-alpha, are not seen. The detection of the broad lines lends support to our interpretation of the UV spectrum, and to our model for Eta Carinae.

To appear in ApJ. 57 pages with 18 figures

References in corpus (20)

• Dynamical Simulations of Magnetically Channeled Line-Driven Stellar Winds: I. Isothermal, Nonrotating, Radially Driven Flow
• In Hot Pursuit of the Hidden Companion of Eta Carinae: An X-ray Determination of the Wind Parameters
• Latitude-dependent effects in the stellar wind of Eta Carinae
• Eta Carinae: Binarity Confirmed
• Dissecting the Homunculus nebula around Eta Carinae with spatially resolved near-infrared spectroscopy
• Direct measurement of the size and shape of the present-day stellar wind of Eta Carinae
• The Binarity of Eta Carinae Revealed from Photoionization Modeling of the Spectral Variability of the Weigelt Blobs B and D
• The 2003 Shell Event in eta Carinae
• On the He II Emission In Eta Carinae and the Origin of Its Spectroscopic Events
• The Purple Haze of Eta Carinae: Binary-Induced Variability?
• Detection of He II 4686 in eta Carinae
• A Change in the Physical State of $\eta$ Carinae?
• The sub-arcsecond dusty environment of Eta Carinae
• Doppler tomography of the Little Homunculus: High resolution spectra of [Fe II] 16435 around Eta Carinae
• Detection of a Hot Binary Companion of $\eta$ Carinae
• Variability of eta Carinae III
• A spectroscopic event of eta Car viewed from different directions: The data and first results
• Eta Carinae's Brightness Variations Since 1998: HST Observations of the Central Star
• The Absorption Spectrum of High-Density Stellar Ejecta in the Line-of-Sight to Eta Carinae
• VLT-UVES observations of the Balmer line variations of eta Carinae during the 2003 spectroscopic event

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