Speaker
Description
Stellar activity phenomena, such as stellar spots, flares, coronal mass ejections are manifestations of the underlying magnetic dynamo, thus studying them is an important input for theoretical models. Doppler imaging is an extensively tested and used spot modeling technique. We utilize this technique to derive Doppler images of well-known active stars (young solar type stars as well as giants, including EK Dra, II Peg, V815 Her, V889 Her, DI Psc) using spectral time series from Piszkéstető observatory from 2022 and 2023. Stellar activity tracers, mostly stellar spots can cause the photocenter of the star to shift from the geometric center. Since spot distributions are non-uniform and active stars rotate rapidly, this photocenter shift can vary over time with the rotation of the star. We use our Doppler maps to calculate the photocenter shifts of these stars caused by the joint effect of rotation and stellar spots and measure its change during a single rotation to estimate the possible effect of this phenomenon on the precision of parallax measurements to see whether it is comparable to the precision of Gaia. Moreover, comparing these shifts on different types of stars could prove an insight into the different types of dynamos working on different stars.
