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| Paper: |
Circumstellar Quasi-periods Accompanying Stellar Periods of Be Stars |
| Volume: |
135, A Half Century of Stellar Pulsation Interpretations: a Tribute to Arthur N. Cox |
| Page: |
348 |
| Authors: |
Stefl, S.; Baade, D.; Rivinius, Th.; Stahl, O.; Wolf, B.; Kaufer, A. |
| Abstract: |
In 1995, 1996, and 1997, several hundred high-resolving power (20,000) echelle spectra (345-862 nm) were for each of the bright southern Be stars 28 CMa, eta Cen and mu Cen obtained with the Heidelberg fiber-coupled echelle spectrograph (HEROS). The results of a Fourier analysis, using also the CLEAN algorithm, of typically 30 spectral lines show that the character of the periodicity probably depends on the site of formation of the lines. Two basic periods are present in each star which differ by typically 0.1 day and can be resolved only in sufficiently long observing series. The main periods, which agree with those detected by previous observations, appear in most lines with constant power distribution across the profiles. The properties of the secondary periods seem to be modified by the size of the envelope as deduced from the width of the rotationally broadened emission lines or, in mu Cen, by variations in the emission strength. The presence and properties of such a `satellite period' can be best demonstrated for 28 CMa. The long-known 1.37-day period dominates in photospheric lines of He I, Si III and Ne I as well as in the cores of most of the other stellar lines. The second period (1.47 days) prevails in the emission lines of the Paschen series and O I and is present also in the wings of the photospheric lines. Both variabilities are of comparable power in the lines of H I, Si II, and Mg II. Possible explanations of and relations between the two variabilities will also be presented. |
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