Aligned, Misaligned and Polar Orbits of Hot Jupiters: Measuring Spin-Orbit Angles via Doppler Tomography with HARPS-N

Abstract

Although the migration of hot Jupiters is not yet fully understood, measurements of the projected spin-orbit angle {\lambda} help shed light on the processes involved. Here we present Doppler tomography of three known hot Jupiters to determine their {\lambda} orientation: HAT-P-49 b, HAT-P-57A b, and XO-3A b. Our analysis explores the impact of cross-correlation processing methods on the detectability and characterization of the planet's Doppler shadow using up to three independent routines for cross-correlation functions extraction; those being: Yabi, iSpec and IRAF. After accounting for differences among the results obtained with the various routines, we report: first, the HAT-P-49 system is a case of a hot Jupiter on a polar orbit with {\lambda}=-85.3{\pm}1.7{\deg}, second, HAT-P-57A indicates practically no deviation of the planet's projected orbit from the host's equatorial plane with {\lambda}=-0.4^{+1.4}_{-1.9}{\deg}, and third, the XO-3A system with the measured value of {\lambda}=38{+3}_{-4}{\deg} lies in between an aligned and a perpendicular orientation, which is a less populated region of the spin-orbit distribution. Our findings highlight both the diversity of spin-orbit angles among close-in giant planets and the potential discrepancies in their measurement that can arise from different approaches to constructing the cross-correlation functions.