LC and RV for HAT-P-15, 17, 21, 26 and 29

The photometric parameters for four of the hot Jupiters were recalculated using 17 new transit light curves, obtained with an array of medium-class telescopes, and data from the TESS space telescope. HATNet time-series photometric data were checked for the signatures of rotation periods of the target stars and their spin axis inclination. From the analysis of the Rossiter-McLaughlin effect we derived a sky-projected obliquity of {lambda}=13{deg}+/-6{deg}, {lambda}=-26.3{deg}+/-6.7{deg}, {lambda=-0.7{deg}+/-12.5{deg}, {lambda}=-26{deg}+/-16{deg}, for HAT-P-15 b, HAT-P-17 b, HAT-P-21 b and HAT-P-29 b, respectively.

Based on theoretical considerations, these small values of {lambda} should be of primordial origin, with the possible exception of HAT-P-21. Due to the quality of the data, we were not able to well constrain {lambda} for HAT-P-26 b, although a prograde orbit is favoured ({lambda}=18{deg}+/-49{deg}). The stellar activity of HAT-P-21 indicates a rotation period of 15.88+/-0.02 days, which allowed us to determine its true misalignment angle {psi}=25{deg}+/-16{deg}.

Our new analysis of the physical parameters of the five exoplanetary systems returned values compatible with those existing in the literature. Using TESS and the available transit lightcurves, we reviewed the orbital ephemeris for the five systems and confirmed that the HAT-P-26 system shows transit timing variations, which may tentatively be attributed to the presence of a third body.