Periodic and aperiodic variations in TT Arietis. Results from an international campaign.

Details Periodic and aperiodic variations in TT Arietis. Results from an international campaign. Periodic and aperiodic variations in TT Arietis. Results from an international campaign.

Aug 1996

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996a%26a...312..121t&link_type=abstract

Astronomy and Astrophysics, v.312, p.121-134

Astronomy and Astrophysics

Astrophysics

22

Stars: Cataclysmic Variables, Stars: Individual: Tt Ari, Stars: Oscillations

Scientific paper

Results based on the 30 best nightly runs are reported. The moments of 33 brightness maxima and 35 minima show large scatter of phases within 0.6^p^-interval. The value of the primary photometric period of P=0.132953+/-13x10^-6^d differs from the previously published ones. Periodograms for detrended nightly runs show significant peaks at different frequencies from 28 to 103c/d. The most prominent peaks correspond to periods of 23.7, 15.2, 27.5 and 51.6min. This argues for transient quasi-periodic oscillations (QPO) occurring at few preferred time scales rather than for a QPO with a time scale decreasing from 27min in 1962 to 17min in 1985 (Semeniuk et al. 1987). Such behaviour may be explained by the "beat-frequency model" (Hollander & van Paradijs 1992). It seems that in TT Ari we observe contributions of several instability mechanisms with similar time scales. At higher frequencies 90-900 c/d the periodogram for all observations obeys a power law with an index γ=1.600+/-0.008. This value coincides within error estimates with that of γ=1.51+/-0.04 obtained for a mean periodogram. Such apparent red noise may be owed to the QPOs. The variations in UBVRI are highly correlated. A method for determination of relative colours of "slow", "fast correlated" variations and an "uncorrelated noise" is proposed. Corresponding parameters are determined. Values U-B=-1.04mag, -1.24mag, -1.35mag and B-V=0.19mag, 0.05mag, 0.12mag for "mean brightness", "fast" and "slow" variations, respectively.

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