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Published December 19, 2008 | Published
Journal Article Open

Reverse engineering a spectrum: using fluorescent spectra of molecular hydrogen to recreate the missing Lyman-α line of pre-main sequence stars

Abstract

The hydrogen Lyman-α (Lyα) line, a major source of ionization of metals in the circumstellar disks of pre-main sequence (PMS) stars, is usually not observed due to absorption by interstellar and circumstellar hydrogen. We have developed a technique to reconstruct the intrinsic Lyα line using the observed emission in the H2 B-X lines that are fluoresced by Lyα. We describe this technique and the subsequent analysis of the ultraviolet (UV) spectra of the TW Hya, RU Lupi and other PMS stars. We find that the reconstructed Lyα lines are indeed far brighter than any other feature in the UV spectra of these stars and therefore play an important role in the ionization and heating of the outer layers of circumstellar disks.

Additional Information

Copyright © 2008 The Royal Swedish Academy of Sciences. Received 17 September 2008, accepted for publication 19 September 2008. Published 19 December 2008. Print publication: Issue T133 (December 2008). This work is funded by Space Telescope Science Institute grant AR-9930 to the University of Colorado. This work is based on observations made in programs 7718, 8041 and 8157 (PIs J L Linsky and F M Walter) of the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

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