XO-2b: a Prograde Planet with Negligible Eccentricity and an Additional Radial Velocity Variation
Abstract
We present precise radial velocities of XO-2 taken with the Subaru HDS, covering two transits of XO-2b with an interval of nearly two years. The data suggest that the orbital eccentricity of XO-2b is consistent with zero within 2σ (e = 0.045 ± 0.024), and that the orbit of XO-2b is prograde (the sky-projected spin-orbit alignment angle λ =; 10° ± 72°). The poor constraint of λ is due to a small impact parameter (the orbital inclination of XO-2b is almost 90°). The data also provide an improved estimate of the mass of XO-2b as 0.62 ± 0.02MJup. Further, we find a long-term radial velocity variation in this system. Additional radial velocity measurements are necessary to specify the cause of this additional variation. </DIV>
- Publication:
-
Publications of the Astronomical Society of Japan
- Pub Date:
- December 2011
- DOI:
- 10.1093/pasj/63.6.L67
- arXiv:
- arXiv:1110.6136
- Bibcode:
- 2011PASJ...63L..67N
- Keywords:
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- stars: binaries: general;
- stars: planetary systems: individual (XO-2);
- stars: rotation;
- techniques: radial velocities;
- techniques: spectroscopic;
- Astrophysics - Earth and Planetary Astrophysics;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 6 pages, 4 figures, 2 tables, PASJ Letters in press