Spectrum of white dwarf stars in NGC 6397

This chart displays the spectra of four White Dwarf stars in globular cluster NGC 6397, obtained with ANTU/FORS1 and identified as such from these data. The spectra were shifted vertically so that they do not overlap. The wavelength is indicated along the abscissa; the intensity along the ordinate. A "standard" spectrum of a White Dwarf star (of spectral type DA - the hydrogen-rich variety) is shown at the top for comparison. Broad absorption lines from hydrogen atoms in the atmosphere are visible. Although the signal-to-noise ratio is quite small, especially for the lower spectra of the fainter stars, they all show the same strong, broad absorption lines as the comparison spectrum. This permits to classify them unambiguously as WD stars. Individual differences, for instance of the widths of the absorption lines, are clearly present and point to different surface gravity and masses.



About the Image

Release date:16 December 1999
Related releases:eso9953
Size:764 x 962 px

About the Object

Name:NGC 6397
Type:Milky Way : Star : Evolutionary Stage : White Dwarf
Milky Way : Star : Grouping : Cluster : Globular
Distance:7000 light years
Category:Star Clusters

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Large JPEG
203.2 KB
Screensize JPEG
260.3 KB

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Very Large Telescope


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