AIP Calendar


Colloquium: Eliana Amazo-Gómez (AIP)

The gradient of power spectra method (GPS): a window to the stellar rotation, and its faculae to spot ratio

Young and active stars usually have regular, almost sinusoidal, patterns of variability attributed to their rotation. At the same time, the majority of older and less active stars, including the Sun, have more complex and non-regular light-curves that do not have a clear rotational modulation signal. Consequently, the rotation periods have been successfully determined only for a small fraction of the Sun-like stars (mainly the active ones) observed by transiting planet-hunting missions, such as CoRoT, Kepler, and TESS. This indicates that only a small fraction of solar analogous have been properly analyzed in terms of rotation and the parameters derived from it. We use GPS, a new method for determining rotation periods of low-activity stars, like the Sun. The method is based on calculating the gradient of the power spectrum (GPS) of stellar brightness variations and identifying the inflection point in such a spectrum. The rotation frequency is then proportional to the frequency of the inflection point. We show that the GPS method returns accurate values of solar rotation independently of the level of solar activity. Furthermore, the novel method gives us constraints on the faculae to spot driver ratio, which consequently could help us to interpret the stellar surface. GPS method has been successfully applied to the retrieval of periods of stars with both regular and non-regular light-curves.

  • Date:
    Feb. 11, 2021, 2:30 p.m. – 3:30 p.m.

  • Location:

    Colloquium Zoom room

  • Contact:
    Silva Järvinen

Last update: 4. February 2021