P-Cygni profile
The P-Cygni profile of a spectral line (named after the typical representative P Cygni ) is created by a stellar wind and is characterized by a broad, unshifted emission line that is limited on the blue side by a narrow, blue-shifted absorption line.
If a star is surrounded by a dense, rapidly expanding envelope, this can be seen in the P-Cygni profile of some of the spectral lines. The blue shift is a consequence of the Doppler effect , because part of the envelope is moving towards the earth. It occurs in absorption because the light emanating from the star is absorbed and scattered in the shell . The part of the envelope that is not directed towards the earth receives excess radiation in the form of the broad emission line. With the help of the P-Cygni profile, the expansion rate and the ion density of the shell can be determined.
P-Cygni profiles include a. has been detected in novae , supernovae , T-Tauri stars , the central stars of planetary nebulae and in the molecular winds of active galaxies .
literature
- James B. Kaler: Stars and their Spectra. Astronomical signals from light . Spektrum Akademischer Verlag, Heidelberg et al. 1994, ISBN 3-86025-089-2 .
- Helmut Scheffler, Hans Elsässer : Physics of the stars and the sun . 2nd revised and expanded edition. BI Wissenschaftsverlag, Mannheim 1990, ISBN 3-411-14172-7 .
Individual evidence
- ^ S. Veilleux et al.: Fast Molecular Outflows in Luminous Galaxy Mergers: Evidence for Quasar Feedback from Herschel. In: The Astrophysical Journal. 776, 27, bibcode : 2013ApJ ... 776 ... 27V .