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FUSE Example Spectra |
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FUSE Example Spectra |
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Date of last change: Dec. 21, 1999
This page contains links to selected examples of FUSE spectra, which are presented in graphical form and, in some instances, compared with previous data sets for context. These particular examples show early data from FUSE before any focussing or optimization of the instrument capabilites have been included, and they are already better than any previous data on these objects by a wide margin! FUSE's sensitivity is excellent, some 10,000 times the sensitivity of the Copernicus satellite that flew in the mid-1970's and looked at the same wavelength range.
In each case, the data shown here are from a small portion of the entire data set. (Each FUSE spectrum is 300 Å [Angstroms] or 30,000 pixels in length!) The captions are given here. Please click on the links to see the spectral plots themselves.
(If looking at "spectra" as "squiggly lines" like this is confusing to you, check out this page for more explanation!)
Active Galaxy Nucleus: FUSE-ORFEUS Comparison This figure shows a comparison of ORFEUS-II (top) and FUSE data (bottom) for the object E141-55, a Seyfert galaxy. (ORFEUS-II was a shuttle-based ultraviolet telescope flown in 1995, which obtained some of the best far-ultraviolet spectra to date for many objects.) The FUSE data are clearly better, showing many details in the spectrum that are confused or invisible in the ORFEUS-II spectrum. Several interstellar absorotion features arising from gas in the Milky Way (along the line-of-sight) are noted in the lower panel, including molecular hydrogen (H2), O VI, and other atomic species. The exposure time for the ORFEUS-II data was roughly 14 ksec. The FUSE exposure time was three times longer, but only a small portion of the total data obtained during that time is shown here. The FUSE data have much higher resolution and signal levels than the ORFEUS data. Note in particular, the presence of weak H2 and atomic lines (e.g., Ar I) visible in the FUSE spectrum that are not visible in the ORFEUS-II spectrum.
White Dwarf spectrum This figure shows a portion of a FUSE spectrum of a white dwarf in the solar neighborhood. These data were obtained with the two silicon carbide channels (i.e. the shortest wavelengths accessible to FUSE) during satellite commissioning activities. These are much shorter wavelengths of ultraviolet light than can be accessed with other satellites such as Hubble Sapce Telescope. Note the clear progression in line strengths of the converging neutral hydrogen Lyman-series absorption lines. The Lyman limit occurs at 912 Angstroms, but the line blanketing of the smallest wavelength lines in the series effectively absorbs away the continuum at longer wavelengths.
White Dwarf: FUSE-ORFEUS Comparison This figure shows a comparison of ORFEUS-I (top) and FUSE data (bottom) for the hot hydrogen-rich white dwarf star G191-B2B. The spectral region shown contains absorption lines due to highly ionized Phosphorus and Silicon in the atmosphere of the star. Note the narrowness of the absorption lines in the FUSE data, and the way FUSE is able to separate the two lines near 1128 Å [Angstroms] that are blended in the ORFEUS spectrum.
Supernova Remnant spectrum This spectrum shows a very different kind of source, a supernova remnant, which is a rapidly expanding bubble of hot gas caused by a stellar explosion in a nearby galaxy. Here, the source emission is in the form of emission lines, which are the "peaks" in these graphical representations of the spectra. The top section of this figure shows a spectrum of the object from the Hopkins Ultraviolet Telescope, which flew on the space shuttle in 1990 during the Astro-1 mission. Most of the emission is from "airglow"--emission from the tenuous remaining atmosphere above the space shuttle at the time of the observation. Only the excess above the dashed line was attributable to the supernova remnant. In the FUSE spectrum at the bottom, the narrow lines are from the airglow, but the two broader lines are the emission from the supernova remnant, now clearly visible. (As a matter of fact, the remnant's lines are broadened by the doppler effect, and show a lot of sub-structure!)
Other examples will be added as time permits!
