Learning about the latitudinal distribution of starspots through the periodogram analysis of photometric data

Abstract

Starspots are cooler and darker than the stellar surface. Therefore, the emitted flux of a star changes when spots are visible on its surface. The presence of spots together with the stellar rotation leads to a periodic modulation on the light curve. By studying that modulation one can then learn about the stellar rotation and also magnetic activity. Recently, Reinhold & Arlt (2015) proposed a method based on the analysis of the Lomb Scargle periodogram of the light curve to identify the sign of the differential rotation, i.e. whether the equator rotates faster than the poles or the opposite. We have been studying in detail the spots' impact on the light curve and on the resulting periodogram. We find that, under some conditions, the periodogram can actually provide an estimate of the true spot latitudes and/or the stellar inclination angle. Moreover, we find that the impact of the spot on the ratio between the heights of the second and first harmonics of the main peaks in the periodogram can be described by a single parameter, the visibility time of the spot. Finally, we also identify possible sources of false positives/negatives for the sign of the differential rotation.

arXiv comment4 pages, 4 figures, proceedings of the Joint TASC2 - KASC9 Workshop - SPACEINN - HELAS8 Conference "Seismology of the Sun and the Distant Stars 2016: Using Today's Successes to Prepare the Future". To be published by the EPJ Web of Conferences

References in corpus (10)

• Rotation and differential rotation of active Kepler stars
• Stellar Limb-Darkening Coefficients for CoRot and Kepler
• Rotation and magnetism of Kepler pulsating solar-like stars. Towards asteroseismically calibrated age-rotation relations
• Rotation periods of 12 000 main-sequence Kepler stars: Dependence on stellar spectral type and comparison with v sin i observations
• Rotation, differential rotation, and gyrochronology of active Kepler stars
• A fast and reliable method to measure stellar differential rotation from photometric data
• Starspot signature on the light curve: Learning about the latitudinal distribution of spots
• A method to discriminate solar and antisolar differential rotation in high-precision light curves
• Lower limit for differential rotation in members of young loose stellar associations
• Spectral characterization and differential rotation study of active CoRoT stars