摘要:Several studies have shown that the occultation of stellar active regions by the
transiting planet can generate anomalies in the high-precision transit light curves, and
these anomalies may lead to an inaccurate estimate of the planetary parameters (e.g., the
planet radius). Since the physics and geometry behind the transit light curve and the
Rossiter-McLaughlin effect (spectroscopic transit) are the same, the Rossiter-McLaughlin
observations are expected to be affected by the occultation of stellar active regions in a
similar way. In this paper we perform a fundamental test on the spin-orbit angles as
derived by Rossiter-McLaughlin measurements, and we examine the impact of the occultation
of stellar active regions by the transiting planet on the spin-orbit angle estimations.
Our results show that the inaccurate estimation on the spin-orbit angle due to stellar
activity can be quite significant (up to ~30 deg), particularly for the edge-on, aligned, and small
transiting planets. Therefore, our results suggest that the aligned transiting planets are
the ones that can be easily misinterpreted as misaligned owing to the stellar activity. In
other words, the biases introduced by ignoring stellar activity are unlikely to be the
culprit for the highly misaligned systems.