ORFEUS OBSERVATIONS OF ULTRAVIOLET EXCITED HIGH-J MOLECULAR HYDROGEN

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We present measurements of diffuse interstellar H(2) absorption lines in the continuum spectra of 10 early-type stars. The data were observed with the Berkeley Extreme and Far-Ultraviolet Spectrometer (BEFS) of the ORFEUS telescope on board the ORFEUS-SPAS I and II space-shuttle missions in 1993 and 1996, respectively. The spectra extend from the interstellar cutoff at 912 angstrom to about 1200 angstrom with a resolution of similar to 3000 and statistical signal-to-noise ratios between 10 and 65. Adopting Doppler broadening velocities from high-resolution optical observations, we obtain the H2 column densities of rotational levels J '' = 0 through 5 for each line of sight. The kinetic temperatures derived from J '' = 0 and 1 states show a small variation around the mean value of 80 K, except for the component toward HD 219188, which has a temperature of 211 K. Based on a synthetic interstellar cloud model described in our previous work, we derive the incident UV intensity I(UV) and the hydrogen density n(H) of the observed components to be -0.4 <= log I(UV) <= 2.2 and 6.3 <= n(H) <= 2500 cm(-3), respectively.
Publisher
KOREAN ASTRONOMICAL SOCIETY
Issue Date
2009-12
Language
English
Article Type
Article
Citation

JOURNAL OF THE KOREAN ASTRONOMICAL SOCIETY, v.42, no.6, pp.145 - 153

ISSN
1225-4614
URI
http://hdl.handle.net/10203/100337
Appears in Collection
PH-Journal Papers(저널논문)
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