Differential Rotation of F G K M Main-Sequence Stars

Context: The Kepler mission spent 9 years discovering exoplanets; however, it also provided valuable information not only about these objects but also more than 200,000 light curves of active stars. From this data, we can measure stellar characteristics such as rotation period and differential rotation.// Aims: Our main goal is to measure differential rotation (DR) using two methods. The first is the ”Two-Peak Method,” developed by Reinhold & Gizon (2015). Their research provided a formula that calculates the DR coefficient based on the difference between the periods of two peaks that are close to each other. The formula (Phigh-Plow)/ Phigh gives the DR parameter, where Phigh and Plow represent periods at higher and lower latitudes, respectively. A positive coefficient indicates solar-like differential rotation, while a negative coefficient indicates anti-solar differential rotation. The second method is the ”Gaussian Distribution Function Method,” which assumes that the full width at half maximum (FWHM) of the periodogram’s Gaussian distribution can be an indicator of the star’s differential rotation. Method: We used the Kepler database (Q0-Q17 quarters) to derive differential rotation for 25,000 F G K M spectral-class stars using the two methods described above. We analysed their light curves using the Lomb-Scargle periodogram. Results: In our research, we identified differential rotation in 500 stars using the “Two-Peak Method” and in 200 stars (with 10 solar-like effective temperature, radius, and rotation period stars) using the “Gaussian Distribution Function Method”. From the first one, we found ∼ 10% asymmetry between solar and anti-solar differential rotation. For these 500 stars, DR was measured for the first time in almost 300 stars. We also present the statistical characteristics (rotation period, temperature, radius, log g, and mass) of these stars in relation to the differential rotation coefficient.