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Astron. Astrophys. 346, 134-138 (1999)

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3. Long-term variation

Thanks to the long duration of the survey, Fig. 1 shows a small amplitude long-term variation in V magnitude and in both Geneva indices [FORMULA] and [FORMULA]. The following comments are to be made:

  • The mean luminosity in V has slightly increased with time during the survey.

  • During this long-term variation, both indices [FORMULA] and [FORMULA] were smaller when the star was brighter in V. Thus, the amplitude of the variation increased towards shorter optical wavelengths.

  • The amplitudes of these mean variations are 0.005 in V, 0.004 in [FORMULA] and 0.012 in [FORMULA].

  • The standard deviations of the measurements around the fitted curves are 0.0046 in V, 0.0047 in [FORMULA] and 0.0057 in [FORMULA]. These values are in good agreement with the precision of the photometric measurements obtained in the Geneva system with our equipment at La Silla (see Burki et al., 1991).

[FIGURE] Fig. 1. V magnitude and Geneva indices [FORMULA] and [FORMULA] measurements of HR 1960. Data from Geneva photometry are identified by filled squares and Hipparcos V magnitudes by crosses. Indications of the mean variations during the 16 years of the survey are drawn.

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© European Southern Observatory (ESO) 1999

Online publication: May 6, 1999