Institut für Astronomie und Astrophysik Abteilung Astronomie Sand 1, D-72076 Tübingen, Germany
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The following two measurements show an example for an emission line spectrum and an absorption line spectrum, respectively. In both cases an original Echelle image as well as the extracted spectrum, composed from all Echelle orders, are shown (see also: How the Echelle Detector registers the Echelle Spectrum).

Example 1: RR Tel

Integration time: 2989 s (sum of 2 measurements)
Count rate: 77 c/s

Echelle image of the spectrum of RR Tel, a symbiotic double star system. In this typical emission line spectrum several bright spots are to be seen. Each of them represents a single spectral line emitted from this double star system. The horizontal bright strip in the center of the image is produced by stray light from both of the two very bright oxygen emission lines (O VI) at 1032 Å and 1037 Å, produced by the Echelle grating. The straylight strip runs exactly horizontal across the image, while the individual spectral orders are slightly tilted.

This is the spectrum ectracted from the image shown above. Shown is the brightness (number of photons per spectral pixel) against the wavelength (in Angstrom, Å). It is clearly seen, that the spectrum nearly solely consists of numerous sharp emission lines.

Example 2: HD 49798

Integration time: 1292 s
Count rate: 6200 c/s

In contrast to the image of RR Tel this image of the Echelle spectrum of the hot star HD 49798 shows the individual spectral orders as bright strips, which are interrupted by several dark narrow regions. These dark regions are absorption lines, which are mainly produced by interstellar matter, located between the star and us, which absorbes the light from the star on its way to the observer. Each atom or ion absorbes light of a characteristic wavelength, thus allowing to determine the chemical and physical composition of the absorbing material.

This image shows the spectrum of HD 49798 extracted from the Echelle orders 40 to 61, which is the total wavelength range from 900 Å to 1410 Å observable with the Echelle spectrometer. For a better distinction the indidivual Echelle orders are plotted in different colors. Besides two very broad stellar absorption lines at 1216 Å (hydrogen Ly-alpha) and 1239/1243 Å (N V, with P-Cygni profile) there are numerous extremely narrow interstellar absorption lines visible.

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| Impressum Last modified 07 Feb 2005