WASP-117b: a 10-day-period Saturn in an eccentric and misaligned orbit
WASP-117b: a 10-day-period Saturn in an eccentric and misaligned orbit
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DOI：
10.1051/0004-6361/201424481
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发表时间：
2014-06
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通讯作者：
M. Lendl;A. Triaud;D. Anderson;A. Cameron;L. Delrez;A. Doyle;M. Gillon;C. Hellier;E. Jehin;P. Maxted;M. Neveu-VanMalle;F. Pepe;D. Pollacco;D. Queloz;D. Ségransan;B. Smalley;A.M.S. Smith;S. Udry;V. Grootel;R. West
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作者：
M. Lendl;A. Triaud;D. Anderson;A. Cameron;L. Delrez;A. Doyle;M. Gillon;C. Hellier;E. Jehin;P. Maxted;M. Neveu-VanMalle;F. Pepe;D. Pollacco;D. Queloz;D. Ségransan;B. Smalley;A.M.S. Smith;S. Udry;V. Grootel;R. West
我们报告了WASP-117b的发现，这是WASP调查发现的第一颗周期超过10天的行星。这颗行星的质量为$M_p=0.2755\pm 0.0089\，M_{J}$，半径$R_p=1.021_{-0.065}^{+0.076}\，R_{J}$，且绕一颗主序F9恒星的轨道是偏心的($e=0.302\pm 0.023$)，$10.02165\pm 0.00055$~d。主星的亮度(V=10.15mag)使它成为一个很好的后续观测目标，它的近星行星平衡温度为T_(Eq)=1225_(-39)^_(+36)$K，行星平均密度较低($Rho_p=0.259_(-0.048)^{+0.054}，\rho_(J))，是在周期为10天的行星中传输光谱的最佳目标之一。根据Rossiter-McLaughlin效应的测量，我们推导出行星轨道与恒星自旋轴之间的投影角为$β=-44\pm11$°，并进一步推导出轨道倾角为$\psi=69.6^+4.7}-4.1°。由于大的轨道间隔，导致行星轨道与恒星平面的轨道环化和重新对准的潮汐作用力很弱，在整个系统寿命期间对行星轨道几乎没有影响。WASP-117b加入了一小部分凌日巨行星的样本，这些行星的轨道特征很好，周期在8天以上。
We report the discovery of WASP-117b, the first planet with a period beyond 10 days found by the WASP survey. The planet has a mass of $M_p= 0.2755 \pm 0.0089 \, M_{J}$, a radius of $R_p= 1.021_{-0.065}^{+0.076}\, R_{J}$ and is in an eccentric ($ e= 0.302 \pm 0.023 $), $ 10.02165 \pm 0.00055 $~d orbit around a main-sequence F9 star. The host star's brightness (V=10.15 mag) makes WASP-117 a good target for follow-up observations, and with a periastron planetary equilibrium temperature of $T_{eq}= 1225_{-39}^{+36}$ K and a low planetary mean density ($\rho_p= 0.259_{-0.048}^{+0.054} \, \rho_{J}$) it is one of the best targets for transmission spectroscopy among planets with periods around 10 days. From a measurement of the Rossiter-McLaughlin effect, we infer a projected angle between the planetary orbit and stellar spin axes of $\beta = -44 \pm 11$ deg, and we further derive an orbital obliquity of $\psi = 69.6 ^{+4.7}_{-4.1}$ deg. Owing to the large orbital separation, tidal forces causing orbital circularization and realignment of the planetary orbit with the stellar plane are weak, having had little impact on the planetary orbit over the system lifetime. WASP-117b joins a small sample of transiting giant planets with well characterized orbits at periods above ~8 days.