Revisiting the Full Sets of Orbital Parameters for the XO-3 System: No Evidence for Temporal Variation of the Spin–Orbit Angle

We present 12 new transit light curves and 16 new out-of-transit radial-velocity measurements for the XO-3 system. By modeling our newly collected measurements together with archival photometric and Doppler velocimetric data, we confirmed the unusual configuration of the XO-3 system, which contains a massive planet ( M P = 11.92 − 0.63 + 0.59 M J ) on a relatively eccentric ( e = 0.2853 − 0.0026 + 0.0027 ) and short-period (3.19152 ± 0.00145 day) orbit around a massive star ( M * = 1.219 − 0.095 + 0.090 M ⊙ ). Furthermore, we find no strong evidence for a temporal change of either V sin i * (and by extension, the stellar spin vector of XO-3), or the transit profile (and thus orbital angular momentum vector of XO-3b). We conclude that the discrepancy in previous Rossiter–McLaughlin measurements (70.0° ± 15.0°; Hébrard et al. 2008; 37.3° ± 3.7°; Winn et al. 2009; 37.3° ± 3.0°; Hirano et al. 2011) may have stemmed from systematic noise sources.