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

Abstract

We present 12 new transit light curves and 16 new out-of-transit radial velocity measurements for the XO-3 system. By modelling 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 ($3.19152\pm 0.00145$day) orbit around a massive star ($M_{\ast }=1.219_{-0.095}^{+0.090}{M}_{\odot }$). Furthermore, we find no strong evidence for a temporal change of either $V\sin i_{\ast }$ (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 ($70.0^{\circ }\pm 15.0^{\circ }$ (Hebrard et al. 2008); $37.3^{\circ }\pm 3.7^{\circ }$ (Winn et al. 2009); $37.3^{\circ }\pm 3.0^{\circ }$ (Hirano et al. 2011)) may have stemmed from systematic noise sources.

Accepted for publication by The Astronomical Journal on January 18, 2022