The ORFEUS II Echelle spectrum of HD 93521: A reference for interstellar molecular hydrogen

Abstract

Abstract. During the second flight of the ORFEUS-SPAS mission in November/December 1996, the Echelle spectrometer was used extensively by the Principal and Guest Investigator teams as one of the two focal plane instruments of the ORFEUS telescope. The spectrum of HD 93521 was obtained during this mission with a total integration time of 1740 s. This spectrum shows numerous sharp interstellar absorption lines. We identified 198 lines of molecular hydrogen including at least 7 lines with a high velocity component. Also most of the 67 identified interstellar metal lines are visible with a high velocity component.We present plots of the complete ORFEUS II Echelle spectrum together with tables of all identified interstellar absorption lines including all 14 detectable H I lines. In addition several identified stellar lines, partially with narrow absorption components, and stellar wind lines are given in a separate table.

Constraints on the Ionization Balance of Hot‐Star Winds fromFUSEObservations of O Stars in the Large Magellanic Cloud

“…The N v and C iv wind profiles of the rapidly rotating Galactic star HD 93521 exhibit similar morphologies, which Massa et al (1995a) and Bjorkman et al (1994) interpreted in terms of an outflow geometry that is cylindrically, not spherically, symmetric. The similarity extends to O vi, which is also characterized by strong emission for comparatively weak absorption in FUV spectra of HD 93521 obtained with the Tübingen Ultraviolet Echelle Spectrometer during the ORFEUS-SPAS mission in 1996 (Barnstedt et al 2000). However, in order to make this morphological connection more convincingly, a reliable HST spectrum is required.…”

An astrophysical oscillator strength for the S II 94.7-nm resonance line and S abundances in DLAs

“…This result gives us further confidence in our f value and suggests that the accuracy is better than these formal error estimates. We warn the readers that the value listed for the S ii λ 94.7‐nm in table 3 of Barnstedt et al (2000) is a guessed value which comes from the Kurucz (1993) data base. This value is almost a factor of 30 larger than our astrophysical value and should not be used in sulphur abundance analysis.…”

“…The most suitable target for this analysis is the well‐known O star HD 93521. The S ii λ 94.7‐nm line has been clearly detected in its ORFEUS II echelle spectrum by Barnstedt et al (2000). In the present paper we perform a quantitative analysis on this feature.…”

“…The ORFEUS data under study here were described in detail by Barnstedt et al (2000) and the instrument description, performance and data reduction by Barnstedt et al (1999). The wavelength coverage ranges from about 91.6 to 141.0 nm with a resolution of .…”

AFUSESURVEY OF THE ROTATION RATES OF VERY MASSIVE STARS IN THE SMALL AND LARGE MAGELLANIC CLOUDS

“…ISMALIGN-FUSE also removes not only the strong interstellar features, but also those chosen (again, interactively) to be weak interstellar features. We cannot overemphasize the importance of removing the considerable number of interstellar lines, whose identification was greatly aided by earlier work of Barnstedt et al (2000), Pellerin et al (2002), and Walborn et al (2002). The spectra are then rectified (routine FUSERECT) to a unit continuum, by fitting a spline function to a series of pseudo-continuum zones in an average spectrum and then dividing each of the spectra by the fit.…”