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Astron. Astrophys. 361, 977-981 (2000)

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New forbidden and fluorescent Fe III lines identified in HST spectra of [FORMULA] Carinae *

S. Johansson 1, T. Zethson 1, H. Hartman 1, J.O. Ekberg 1, K. Ishibashi 2,3, K. Davidson 2 and T. Gull 3

1 Department of Physics, Lund University, P.O. Box 118, 22100 Lund, Sweden (sveneric.johansson, torgil.zethson, henrik.hartman, jan_olof.ekberg@fysik.lu.se)
2 Astronomy Department, University of Minnesota, 116 Church St. SE, Minneapolis, MN 55455, USA (bish@howdy.gsfc.nasa.gov; kd@ea.spa.umn.edu)
3 NASA/Goddard Space Flight Center, Code 681, Greenbelt, MD 20771, USA (gull@sea.gsfc.nasa.gov)

Received 21 March 2000 / Accepted 6 July 2000

Abstract

We discuss the origin of eight emission lines in the spectra of gas blobs close to the central star of [FORMULA] 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 HLy[FORMULA] 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. [FORMULA]Fe III[FORMULA] in the case of doubly ionized iron.

Key words: atomic processes – line: identification – stars: individual: j Car – stars: variables: general – ultraviolet: stars

* Based on observations with the NASA/ESA Hubble Space Telescope, and supported by grant numbers GO-6501 and GO-7302 from the Space Telescope Science Institute. The STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

Send offprint requests to: S. Johansson

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© European Southern Observatory (ESO) 2000

Online publication: October 10, 2000
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