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Detection of 12 micron Mg I and OH lines in stellar spectraInfrared lines of Mg I and OH have been detected in stellar spectra near 12.3 microns. The Mg I 7i-6h transition was seen in Alpha Ori and Alpha Tau, and the R2e(23.5) and R1f(24.5) transitions of OH were seen in Alpha Ori. All lines appear in absorption, in contrast to the solar spectrum where the Mg I line shows a prominent emission core. The lack of emission in these low surface gravity stars is due to a greatly reduced volume recombination rate for the high-n states of Mg I, which is not fully compensated by the increased chromospheric scale height. The OH equivalent widths are sensitive to the temperature structure of the upper photosphere of Alpha Ori, and they indicate that the photosphere near tau 5000 of about 10 to the -5th is approximately 100 K hotter than is given by flux constant models. The OH measurements agree more closely with the 1981 semiemprical model of Basri, Linsky, and Eriksson (1981), which is based on Ca II and Mg II ultraviolet features.
Document ID
Document Type
Reprint (Version printed in journal)
External Source(s)
Jennings, D. E. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Deming, D. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Wiedemann, G. R. (Max-Planck-Institut fuer extraterrestrische Physik Garching, Germany)
Keady, J. J. (Los Alamos National Laboratory NM, United States)
Date Acquired
August 13, 2013
Publication Date
November 1, 1986
Publication Information
Publication: Astrophysical Journal, Part 2 - Letters to the Editor
Volume: 310
ISSN: 0004-637X
Subject Category
Distribution Limits