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Detailed Far-UV Spectral Atlas of B Main Sequence Stars

Myron A. Smith

The far-UV spectral atlas of B stars (Smith 2010) contains high resolution data in the far-UV wavelength region (defined here as the range 949-1225 Ångstroms) for 10 B stars near the main sequence. The spectrum for type B0 is taken, with permission from the author, from the still classic Copernicus satellite atlas of τ Scorpii (Rogerson and Upson 1977). For all other types the spectra were obtained from the MAST/FUSE data archives (Far Ultraviolet Spectroscopic Explorer) in the range 949-1188Å, and from the archives of either the HST/STIS or IUE archives for wavelengths above 1188Å; whenever both data sources were available the STIS spectrum was selected. This atlas has been published by the IOP (Institute of Physics) Press as an Astrophysical Journal Supplement both in paper and on-line formats. The FITS-formatted data on which the atlas is based are available only through this website.

With respect to the data in the MAST archives, the altas spectra are enhanced, first, in that wavelength irregularities for the FUSE Side 1 and Side 2 spectra have been removed to the extent possible and corrections made for the stars' radial velocities. The spectra were then resampled to restore the wavelength zeropoints and increments of the original spectra. Second, the depressed fluxes in the FUSE 1B LiF detector segment due to the primary "worm" have been corrected by means of the quasi-continuum fluxes in the 2A LiF segment. Third, a "star/ISM flag" vector was added to the FITS files to designate those wavelengths for which the fluxes are dominated by local molecular hydrogen lines.

This work is practically unique among stellar spectral atlases in its attempt to identify all visible photospheric and interstellar lines in this wavelength region by means of existing atomic and molecular line sources. For this reason it is called a "detailed" spectral atlas. These identifications are shown in a long table containing three subtables. These are referred to as Tables 3a-c in the Journal paper, and each includes about two thousand line identifications. The lines are designated as either "primary" or "secondary" for each of three spectral types, B0, B2, and B8, where the attached secondary lines have smaller equivalent widths than the primary lines within a common wavelength instrumental resolution of 0.05Å and 0.075Å for Copernicus and FUSE, respectively.

This atlas also presents expanded plots and line identification tables of the entire wavelength range for spectra at types B0, B2, and B8 approximately representing the extremes and middle of the ionizations of iron in the B range. When secondary lines contribute to line blends, the total number of features in a wavelength bin is given following the wavelength/ion identification string. Molecular hydrogen lines and spectral regions are shown by vertical red tick marks. The FUSE Side 1 and 2 spectra are shown as large dots and green lines, respectively. (The Copernicus spectrum for type B0 is a single spectrum.)

The links at the top and bottom of the next page table allow downloading of the spectral data in FITS format. A link is also given to the extensive line identification tables for photospheric and ISM lines in the B0, B2, B8 template spectra, and a table lists the 3-panel spectral plots corresponding to Figures 1 and 2 in the Journal paper (each figure panel covers 7.5Å). A detailed README file is also provided, which describes the contents of these files in some detail.

Spectral Types of Far-UV Atlas Stars

Star Sp. Type Teff Source
τ Sco* B0.2V 30400K Copernicus
(same*) Copernicus
HD 113012 B0 III 29200K FUSE
(τ Sco) B0.2V 30400K Copernicus
HD 102475 B0 III V 26100K FUSE
1 CMa) (B1 III) (26200K) IUE
HD 37367* B2 IV-V 21600K FUSE
(γ Peg*) (B2 IV) (22500K) IUE
HD 45057 B3 V 21600K FUSE
(ς Cas) (B2 IV) (20900K) IUE
HD 201836 B4 IV 18620K FUSE
(ι Her) (B3V) (17800K) IUE
HD 94144 B5 III 17100K FUSE
(same) STIS
HD 30122 B6 V 15500K FUSE
(same) (B6 V) STIS
HD 182308* B8 Vp 13800K FUSE
(ξ Oct*) (B8 V) (14100K) IUE
HD 62714 B9 Vp 12800K FUSE
(same) STIS

• τ Sco uses Copernicus atlas spectrum (Rogerson & Upson 1977).
• First row in each cell refers to star with FUSE spectra (≤1188Å).
    Second row in italics and parentheses refers to star with HST/STIS or IUE spectra (>1188Å).
• Spectra of asterisked stars are used for line identifications.
• Walborn et al. (IUE B Star atlas in NASA Pub. 1363, 1995) gives the spectral type for ξ1 CMa as B0.7 IV.
• The "p" designations for the types of HD 182308 and HD 62714 signify that these spectra are members of the (B peculiar) HgMn subgroup.
• Optical studies of τ Sco and ζ Cas indicate that these stars are magnetic. Their middle-UV resonance (wind) lines are anomalous.

It is to be anticipated that the line lists may require occasional corrections or additions as new atomic line data become available. If so, these addenda will be noted under the "Revisions/Errata" link located on the next page. These additions will supercede the contents of the journal paper in those respects. Comments and questions concerning the atlas may be directed to the author at msmith AT

Available Data