We present a preliminary analysis of magnetic activity cycles in a sample of solar-type stars for which both primary and possible secondary magnetic cycles were identified from long-term chromospheric activity indicators. Magnetic cycle periods were estimated using time series of the S-index and Bisector Inverse Slope (BIS) for stars selected from the catalogue of Gaia Radial Velocity (RV) standard stars. Significant periodicities were determined using the Generalized Least Squares (GLS) periodogram.
Eight stars in the sample show possible evidence of secondary magnetic cycles. For these stars exhibiting dual-cycle signatures, we computed the period and amplitude ratios to investigate the potential coexistence of distinct dynamo modes. The period ratios span a broad range from 0.3 to 2.2, suggesting both shorter secondary cycles—consistent with the 1.6-year solar quasi-biennial oscillations—and longer secondary cycles relative to the primary one, which may indicate possible cycle dominance switching or beating dynamo behavior. The amplitude ratios range from 0.1 to 1.4, implying that, in some stars, the secondary signal is weak and possibly noise-dominated, while in others it is comparable in strength to the primary cycle.
Although preliminary, these results support the idea that multi-periodic magnetic activity is not uncommon among solar-type stars and may offer valuable constraints for dynamo theory.