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Astron. Astrophys. 352, 287-296 (1999)


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ORFEUS II echelle spectra: deuterium and molecular hydrogen in the ISM towards BD+39 3226 *

H. Bluhm 1, O. Marggraf 1, K.S. de Boer 1, P. Richter 1 and U. Heber 2

1 Sternwarte der Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
2 Dr. Remeis-Sternwarte, Astronomisches Institut der Universität Erlangen-Nürnberg, Sternwartstrasse 7, 96049 Bamberg, Germany

Received 25 June 1999 / Accepted 21 October 1999

Abstract

In ORFEUS II spectra of the sdO star BD +39 3226 interstellar hydrogen and deuterium is detected. From Ly [FORMULA] profile fitting and a curve of growth analysis of the Lyman series of HI and DI we derive the column densities [FORMULA] cm-2 and [FORMULA] cm-2. From the analysis of metal absorption lines in ORFEUS and IUE spectra we obtain column densities for 11 elements. In addition, we examine absorption lines of H2 for rotational excitation states up to [FORMULA]. We find an H2 ortho-to-para ratio of 2.5, the fractional abundance of molecular hydrogen has a low value of [FORMULA] for a total amount of [FORMULA]cm-2. The column densities of the excitation states reveal a moderate Boltzmann excitation temperature of 130 K and an equivalent excitation temperature for the excited upper states due to UV pumping of [FORMULA] K.

Key words: space vehicles – stars: individual: BD +39 3226 – ISM: abundances – ISM: molecules – cosmology: miscellaneous – ultraviolet: ISM

* Based on data obtained under the DARA ORFEUS guest observer programme

Send offprint requests to: H. Bluhm (hbluhm@astro.uni-bonn.de)

© European Southern Observatory (ESO) 1999

Online publication: November 23, 1999

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