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| en:praktikum:massenverlust [2016/10/07 23:44] – [Correlation with the X-Ray luminosity] rhainich | en:praktikum:massenverlust [2017/09/07 15:39] (current) – [Correlation with the X-Ray luminosity] rhainich |
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| Massive, hot stars (spectral types O and B) emit parts of their radiation in the Radio band. [[http://adsabs.harvard.edu/abs/1975MNRAS.170...41W|Wright & Barlow (1975)]] developed a simple model to calculate free-free-emission of stellar winds (see the script of the stellar atmospheres lecture!). At least of three OB stars (e.g. HD66811 ($\zeta$ Puppis), HD152408, HD169454) there are Radio measurements at different frequencies that show the predicted frequency profile. Multiple measurements show similar results (i.e. no variation with time). Both combined suggest that the model of Wright & Barlow is valid for these stars. A number of such measurements were taken with the most powerful Radio telescope in the world, the VLA (Very Large Array). (Data can e.g. be found in the Wendker 1995 catalog.) | Massive, hot stars (spectral types O and B) emit parts of their radiation in the Radio band. [[http://adsabs.harvard.edu/abs/1975MNRAS.170...41W|Wright & Barlow (1975)]] developed a simple model to calculate free-free-emission of stellar winds (see the script of the stellar atmospheres lecture!). At least of three OB stars (e.g. HD66811 ($\zeta$ Puppis), HD152408, HD169454) there are Radio measurements at different frequencies that show the predicted frequency profile. Multiple measurements show similar results (i.e. no variation with time). Both combined suggest that the model of Wright & Barlow is valid for these stars. A number of such measurements were taken with the most powerful Radio telescope in the world, the VLA (Very Large Array). (Data can e.g. be found in the Wendker 1995 catalog.) |
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| Estimate the mass loss rate $\dot{M}$ of the three stars mentioned before from the free-free Radio emission following the formula given by Wright & Barlow. The formula has three **input parameters**: The Radio flux at a given frequency, the distance and the "terminal velocity" of the stellar wind. Get the needed measurements from the acquainted databases in the internet ([[http://simbad.u-strasbg.fr/|Simbad]], [[http://vizier.u-strasbg.fr/viz-bin/VizieR|VizieR]]). | Estimate the mass-loss rate $\dot{M}$ of the three stars mentioned before from the free-free Radio emission following the formula given by Wright & Barlow. The formula has three **input parameters**: The Radio flux at a given frequency, the distance and the "terminal velocity" of the stellar wind. Get the needed measurements from the acquainted databases in the internet ([[http://simbad.u-strasbg.fr/|Simbad]], [[http://vizier.u-strasbg.fr/viz-bin/VizieR|VizieR]]). |
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| ===== Correlation with the X-Ray luminosity ===== | ===== Correlation with the X-Ray luminosity ===== |
| It's interesting to note, that OB stars also emit X-rays. X-ray count rates can also be found at [[http://simbad.u-strasbg.fr/simbad/|Simbad]]. Also check (under the assumption of the distance used for the $\dot{M}$ estimation) if the X-ray luminosity scales with the mass loss rate. | It's interesting to note, that OB stars also emit X-rays. X-ray count rates can also be found at [[http://simbad.u-strasbg.fr/simbad/|Simbad]]. Also check (under the assumption of the distance used for the $\dot{M}$ estimation) if the X-ray luminosity scales with the mass-loss rate. |
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| Prepare a laboratory course protocol, as usual (determine the mass-loss rate and deduce the necessary formula, plot the P-Cygni profile). | Prepare a laboratory course reprot, as usual (determine the mass-loss rate and deduce the necessary formula, plot the P-Cygni profile). |
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| [[en:praktikum:index|Overview: Laboratory Courses]] | [[en:praktikum:index|Overview: Laboratory Courses]] |
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