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HST/GHRS Spectral Atlas of the M2 Iab Star Alpha Orionis

This page brings you to an ultraviolet atlas of Alpha Orionis (Betelgeuse) constructed by members of the HST Goddard High Resolution Spectrograph (GHRS) scientific development and calibration teams. This star was chosen because of extensive observations of it from ground-based spectrographs, photometers, and interferometers in the optical and IR spectral regions and because of the time coverage of its variations from ground sites and the IUE satellite by many observers.

The spectral data were recorded on 1992 Septmber 24 using the GHRS Small Science Aperture (SSA). (Note that these observations were done before the installation of the COSTAR corrective optic element.) The atlas consists of a number of plots of relative flux versus wavelength over the range 1979 -- 3300 Å. The data were recorded through the Large Science Aperture (LSA) by 4:1 substepping the G270M (medium resolution) grating over an angle corresponding to one pixel at the detector. The pixel-to-pixel sampling decreases with increasing wavelength from 3.7 to 2.0 km/s, or about 1/4 of a resolution element. The signal to noise in "continuum pixels" varies from 3 near 2000 Ångstroms to about 30 at 3000 Ångstroms; in the emission lines the SNR is somewhat higher. Full details of these observations are given by Brandt et al. (1995).

Taking into account the signal to noise, wavelength range, and the wealth of unblended sharp lines, this is possibly the most comprehensive ultraviolet spectral atlas of a cool star published to date. Wavelength identifications were obtained primarily from lines already observed in this star and other luminous red stars by the IUE. Laboratory measurements were taken from R. L. Kelly (J. Phys. & Chem Ref. Data, 16, Suppl. No. 1, 1987).

The "Data" consist of two-column ascii files listing the wavelengths (Ångstroms) and flux (10^9 ergs cm^2/s/Å); the column headers must be stripped before being numbers are read. The identifier "ID" lists both measured and laboratory wavelengths; the sources for the latter are given in the Brandt et al. paper. Note that some fluxes in the original data are negative; these have been set artificially to zero.

Available Data

Copyright Statement: The data presented here were published in the Astronomical Journal. and appear with the permission of the American Astronomical Society and the authors cited above. Reuse or redistribution of these data is subject to the copyright policies of the American Astronomical Society.