New forbidden and fluorescent Fe III lines identified in HST spectra of η Carinae

S. Johansson, T. Zethson, H. Hartman, J. O. Ekberg, K. Ishibashi, Kris Davidson, T. Gull

Research output: Contribution to journalArticle

46 Scopus citations

Abstract

We discuss the origin of eight emission lines in the spectra of gas blobs close to the central star of η Carinae. The spectra have been obtained with the Goddard High Resolution Spectrograph (GHRS) and the Space Telescope Imaging Spectrograph (STIS) onboard the Hubble Space Telescope. Between 2400 and 2500 Å five narrow lines are identified as new forbidden lines of doubly ionized iron, [Fe III]. We present gA-value data for the corresponding transitions, which combine two different metastable configurations of Fe III. An anomalous intensity of the narrow Fe III line (UV 34) at 1914 Å is explained as fluorescence due to HLyα pumping. A level mixing of about 1% increases the f-value of the pumped excitation channel by more than two orders of magnitude, which makes the pumping efficient and the fluorescence significant. We introduce a new designation for fluorescence lines photoexcited by an accidental resonance, eg. 〈Fe III〉 in the case of doubly ionized iron.

Original languageEnglish (US)
Pages (from-to)977-981
Number of pages5
JournalAstronomy and Astrophysics
Volume361
Issue number3
StatePublished - Dec 1 2000

Keywords

  • Atomic processes
  • Line: identification
  • Stars: individual: η Car
  • Stars: variables: general
  • Ultraviolet: stars

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    Johansson, S., Zethson, T., Hartman, H., Ekberg, J. O., Ishibashi, K., Davidson, K., & Gull, T. (2000). New forbidden and fluorescent Fe III lines identified in HST spectra of η Carinae. Astronomy and Astrophysics, 361(3), 977-981.