WISEA J114724 .10-204021.3：TW Hya协会的自由浮动行星质量成员
WISEA J114724.10-204021.3: A Free-Floating Planetary Mass Member of the TW Hya Association
摘要：
我们介绍了WISEA J114724.10 $-$ 204021.3，一个年轻的，低质量的，高概率的TW Hya协会成员。WISEA J114724.10 $-$ 204021.3是基于它的红色AllWISE颜色（W1 $-$ W2 = 0.63等）和极红的2 MASS $J-K_{\rm S}$颜色（$>$ 2.64等）发现的，后者是由VISTA半球测光测量的近红外线确认的（$J-K_{\rm S}$ = 2.57 $\pm$ 0.03）。后续近红外光谱显示光谱类型的L7 $\pm$ 1以及几个光谱指标的青年。这些特征包括峰值$H$ -带形状和较陡的$K$ -带斜率，这些特征通常归因于低表面重力。WISEA J114724.10 $-$ 204021.3的天空位置、自行和距离估计值都与$\sim$ 1000万年前TW Hya星协的成员一致。使用TW Hya协会和演化模型的年龄，我们估计WISEA J114724.10 $-$ 204021.3的质量为5 $-$ 13 $M_{\rm Jup}$，使其成为太阳附近发现的最年轻和质量最低的自由漂浮物体之一。
英文摘要：
We present WISEA J114724.10$-$204021.3, a young, low-mass, high probability member of the TW Hya association. WISEA J114724.10$-$204021.3 was discovered based on its red AllWISE color (W1$-$W2 = 0.63 mag) and extremely red 2MASS $J-K_{\rm S}$ color ($>$ 2.64 mag), the latter of which is confirmed with near-infrared photometry from the VISTA Hemisphere Survey ($J-K_{\rm S}$ = 2.57$\pm$0.03). Follow-up near-infrared spectroscopy shows a spectral type of L7 $\pm$ 1 as well as several spectroscopic indicators of youth. These include a peaked $H$-band shape and a steeper $K$-band slope, traits typically attributed to low surface gravity. The sky position, proper motion, and distance estimates of WISEA J114724.10$-$204021.3 are all consistent with membership in the $\sim$10 Myr old TW Hya association. Using the age of the TW Hya association and evolutionary models, we estimate the mass of WISEA J114724.10$-$204021.3 to be 5$-$13 $M_{\rm Jup}$, making it one of the youngest and lowest mass free-floating objects yet discovered in the Solar neighborhood.
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