Open AccessThe light curve of the semiregular variable L 2 Puppis – II. Evidence for solar‐like excitation of the oscillations
Author(s) -
Bedding T. R.,
Kiss L. L.,
Kjeldsen H.,
Brewer B. J.,
Dind Z. E.,
Kawaler S. D.,
Zijlstra A. A.
Publication year - 2005
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2005.09281.x
Subject(s) - physics , astrophysics , light curve , excitation , envelope (radar) , phase (matter) , variable star , red giant , spectral density , astronomy , stars , statistics , quantum mechanics , telecommunications , radar , computer science , mathematics
We analyse visual observations of the pulsations of the red giant variable L 2 Puppis (L 2 Pup). The data cover 77 yr between 1927 and 2005, thus providing an extensive empirical base for characterizing properties of the oscillations. The power spectrum of the light curve shows a single mode resolved into multiple peaks under a narrow envelope. We argue that this results from stochastic excitation, as seen in solar oscillations, with a mode lifetime of about 5 yr. The random fluctuations in phase also support this idea. A comparison with X Cam, a true Mira star with the same pulsation period, and W Cyg, a true semiregular star, illustrates the basic differences in phase behaviours. The Mira shows very stable phase, consistent with excitation by the κ‐mechanism, whereas W Cyg shows large phase fluctuations that imply stochastic excitation. We find L 2 Pup to be intermediate, implying that both mechanisms play a role in its pulsation. Finally, we also checked the presence of low‐dimensional chaos and could safely exclude it.