The XV International GEOS Symposium was held in Selvino, near Bergamo (Italy), from 24 to 26 April 1992, with 22 participants representing Italy, France and Switzerland. The meeting included scientific communications on variable star research and a final session devoted to GEOS scientific management.
The scientific program focused mainly on eclipsing binaries, variable star photometry, and the growing use of digital signal processing techniques.
A. Gaspani presented the CBLCS code, a portable FORTRAN77 program developed to solve light curves of contact binaries by optimizing the parameters f, q and i. Several additional contributions by the same author introduced linear digital filtering, signal restoration, and matched/optimal filtering applied to variable star observations, with particular emphasis on noise characterization in visual and photoelectric data.
Observational results on eclipsing binaries were extensively discussed. Studies of RZ Cas (M. Dumont, G. Galli) revealed shortterm variability in the shape of the primary minimum, possibly related to rapid changes in circumstellar matter. O. Walas presented initial analyses of understudied eclipsing binaries and proposed RS Serpentis as a nearcontact system with mass ratio close to unity, while stressing the need for additional photoelectric coverage.
Cepheid variability issues were reviewed by G. Boistel through the case of PP Aql.
Instrumentation and observing techniques were addressed through presentations on the Ganda Astronomical Observatory project, automated photographic photometry, and CCD photometry procedures. The importance of working on unfiltered CCD data (“Dirty Flux Curves”) prior to signal processing was emphasized.
S. Spagocci introduced a statistical model describing observer memory effects in visual estimates, capable of reproducing common systematic distortions. Results obtained by GEOS members during the PHEMU92 campaign were reported, showing that highprecision timings of mutual satellite events can be achieved with appropriate processing techniques. A multitechnique international campaign on ο Andromedae was also announced.
The GEOS management session confirmed a stable membership (95–100 members) and satisfactory observational activity but noted an insufficient number of GEOS Circulars. Members were encouraged to contribute more regularly. The need for methodological standardization, particularly through the adoption of modern digital signal processing techniques, was strongly emphasized. The annual Italian GEOS Meeting will be held in Aviatico (BG) on 31 October – 1 November 1992.
The Symposium confirmed the central role of advanced data analysis techniques and coordinated observational efforts in the future scientific activity of the GEOS.