ForumSpringerAstron. Astrophys.
ForumWhats NewSearchOrders

Astron. Astrophys. 329, 147-154 (1998)

Table of Contents
Available formats: HTML | PDF | (gzipped) PostScript

Analysis of the irregular pulsations of AC Herculis

Z. Kolláth 2, 1, J.R. Buchler 1, T. Serre 3 and J. Mattei 4

1 Physics Department, University of Florida, Gainesville, FL 32611, USA (buchler@ phys.ufl.edu)
2 Konkoly Observatory, Budapest, Hungary (kollath@ buda.konkoly.hu)
3 Observatoire de Paris, Meudon, France
4 AAVSO, Cambridge, MA 02138, USA

Received 13 June 1997 / Accepted 12 August 1997


The AAVSO lightcurve data of the irregularly pulsating star AC Herculis of the RV Tau class are analysed. The lightcurve is shown not to be compatible with a periodic, or even multiperiodic pulsation, even if allowance is made for evolution. Instead the best explanation is that the irregularly alternating cycles are a manifestation of low dimensional chaos. Our flow reconstruction suggests that the dynamics can be successfully embedded in 3 dimensions. Further, the (Lyapunov) fractal dimension of the underlying dynamic attractor is computed to be [FORMULA], independent of the dimension of the reconstruction space. It is smaller than the value of [FORMULA] 3.1 found for the more irregular lightcurve of R Sct. From these results we are led to conclude that the lightcurve is likely to have been generated by a 3 dimensional dynamics, i.e. by 3 first order ODEs. In simpler language, it expresses the remarkable fact that the observational value at any time [FORMULA] is a unique function h of the values at only three preceding observations, viz. [FORMULA].

Key words: stars: individual: AC Her – stars: oscillations – methods: data analysis – methods: numerical – chaos

© European Southern Observatory (ESO) 1998

Online publication: November 24, 1997