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arXiv 1004.3965astro-ph.SRastro-ph.EP
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G 196- 3 B的红外和运动学性质

Infrared and kinematic properties of the substellar object G 196-3B

M. R. Zapatero Osorio, R. Rebolo, G. Bihain, V. J. S. Béjar, J. A. Caballero, C. Álvarez

备注：
Accepted for publication in ApJ.
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摘要：

我们报告不寻常的近红外和中红外测光性能的G 196-3 B，年轻的亚恒星同伴在16角秒从活跃的M2.5型恒星G 196-3 A，使用的数据与IRAC和MIPS仪器机载斯皮策。G 196-3 B在从1.6到24微米的所有波长处显示出比其光谱类型预期的明显更红的颜色，这是在L3处从光学和近红外光谱确定的。我们讨论了各种物理场景来解释它的红色性质，并得出结论，低重力的大气层与遮蔽的上层大气层和/或温暖的尘埃盘/信封提供了最可能的解释，他们两个一致的时间间隔在20-300万年。我们还提出了新的和准确的单独自行测量G 196-3 A和B确认，这两个对象的引力联系，并在几个质量/年内共享相同的运动。在对组合的分光光度光谱能量分布进行积分后，我们得到G 196-3 A和B的测热星等差为6.15 +/- 0.10 mag. Kinetic consideration of the Galactic space motions of the system for distance in interval 15-30 pc暗示这对星系可能是本星系协的成员，它位于年轻星团的过去位置附近，如英仙座α星，不到8500万年前，那里可能是双星的起源地。在这些年轻的年龄，G 196-3 B的质量将在12-25兆焦耳的范围内，接近行星和褐矮星之间的边界。

英文摘要：

We report unusual near- and mid-infrared photometric properties of G 196-3 B, the young substellar companion at 16 arcsec from the active M2.5-type star G 196-3 A, using data taken with the IRAC and MIPS instruments onboard Spitzer. G 196-3 B shows markedly redder colors at all wavelengths from 1.6 up to 24 micron than expected for its spectral type, which is determined at L3 from optical and near-infrared spectra. We discuss various physical scenarios to account for its reddish nature, and conclude that a low-gravity atmosphere with enshrouded upper atmospheric layers and/or a warm dusty disk/envelope provides the most likely explanations, the two of them consistent with an age in the interval 20-300 Myr. We also present new and accurate separate proper motion measurements for G 196-3 A and B confirming that both objects are gravitationally linked and share the same motion within a few mas/yr. After integration of the combined spectrophotometric spectral energy distributions, we obtain that the difference in the bolometric magnitudes of G 196-3 A and B is 6.15 +/- 0.10 mag. Kinematic consideration of the Galactic space motions of the system for distances in the interval 15-30 pc suggests that the pair is a likely member of the Local Association, and that it lay near the past positions of young star clusters like alpha Persei less than 85 Myr ago, where the binary might have originated. At these young ages, the mass of G 196-3 B would be in the range 12-25 Mjup, close to the frontier between planets and brown dwarfs.

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