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Published August 10, 2013 | Published
Journal Article Open

Unexpected Ionization Structure in Eta Carinae's "Weigelt Knots"

Abstract

The Weigelt knots, dense slow-moving ejecta near η Carinae, are mysterious in structure as well as in origin. Using spatially dithered spectrograms obtained with the Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS), we have partially resolved the ionization zones of one knot. Contrary to simple models, higher ionization levels occur on the outer side, i.e., farther from the star. They cannot represent a bow shock, and no satisfying explanation is yet available—though we sketch one qualitative possibility. STIS spectrograms provide far more reliable spatial measurements of the Weigelt knots than HST images do, and this technique can also be applied to the knots' proper motion problem. Our spatial measurement accuracy is about 10 mas, corresponding to a projected linear scale of the order of 30 AU, which is appreciably smaller than the size of each Weigelt knot.

Additional Information

© 2013 The American Astronomical Society. Received 2013 January 31; accepted 2013 June 1; published 2013 July 22. G.N.R. is supported by a Hertz Foundation Fellowship. We thank Beth Perriello and other consultants at STScI for assistance with the HST observing techniques. Based on observations made with the NASA/ESA Hubble Space Telescope. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under the NASA contract NAS 5-26555.

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August 19, 2023
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