PSO J318的径向速度和自转速度
The Radial and Rotational Velocities of PSO J318.5338$-$22.8603, a Newly Confirmed Planetary-Mass Member of the $β$ Pictoris Moving Group
摘要：
PSO J318.5338 $-$ 22.8603是一个极红的行星质量天体，根据其空间位置和切向速度，已被确定为$β$如画移动群的候选成员。我们提出了一个高分辨率的$K$带谱PSO J318.5338 $-$ 22.8603。使用前向建模马尔可夫链蒙特卡罗方法，我们报告的径向速度和$v$ sin（$i$）的PSO J318.5 $-$ 22，$-$ 6.0 $^{+0.8}_{-1.1}$ km s $^{-1}$和17.5 $^{+2.3}_{-2.8}$ km s $^{-1}$，分别第一次测量。我们计算了PSO J318.5 $-$ 22的空间速度和位置，确认它是$β$ Picture移动群的成员。采用PSO J318.5 $-$ 22的23 $\pm$ 300万年的年龄，我们使用进化模型确定了$8.3\pm0.5$ $M_{\rm{Jup}}$的质量和$1127^{+24}_{-26}$ K的有效温度。PSO J318.5338 $-$ 22.8603的质量和温度都介于直接成像的行星$β$ Picturesb和51 Eridani b之间，使其成为$β$ Picturesb移动群行星质量成员序列中的重要基准天体。结合我们的$v$ sin（$i$）测量和最近的光度变化数据，我们将PSO J318.5 $-$ 22的倾角限制为$>29^{\circ}$，其旋转周期为5-10.2小时。PSO J318.5 $-$ 22的赤道速度表明，它的自转与太阳系行星的速度-质量关系的外推是一致的。
英文摘要：
PSO J318.5338$-$22.8603 is an extremely-red planetary-mass object that has been identified as a candidate member of the $β$ Pictoris moving group based on its spatial position and tangential velocity. We present a high resolution $K$-band spectrum of PSO J318.5338$-$22.8603. Using a forward-modeling Markov Chain Monte Carlo approach, we report the first measurement of the radial velocity and $v$ sin($i$) of PSO J318.5$-$22, $-$6.0$^{+0.8}_{-1.1}$ km s$^{-1}$ and 17.5$^{+2.3}_{-2.8}$ km s$^{-1}$, respectively. We calculate the space velocity and position of PSO J318.5$-$22 and confirm that it is a member of the $β$ Pictoris moving group. Adopting an age of 23$\pm$3 Myr for PSO J318.5$-$22, we determine a mass of $8.3\pm0.5$ $M_{\rm{Jup}}$ and effective temperature of $1127^{+24}_{-26}$ K using evolutionary models. PSO J318.5338$-$22.8603 is intermediate in mass and temperature to the directly-imaged planets $β$ Pictoris b and 51 Eridani b, making it an important benchmark object in the sequence of planetary-mass members of the $β$ Pictoris moving group. Combining our $v$ sin($i$) measurement with recent photometric variability data, we constrain the inclination of PSO J318.5$-$22 to $>29^{\circ}$ and its rotational period to 5-10.2 hours. The equatorial velocity of PSO J318.5$-$22 indicates that its rotation is consistent with an extrapolation of the velocity-mass relationship for solar system planets.
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