ALMA observations of the nearby AGB star L2 Puppis - I. Mass of the central star and detection of a candidate planet
ALMA observations of the nearby AGB star L2 Puppis - I. Mass of the central star and detection of a candidate planet
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ALMA 对附近 AGB 恒星 L2 Puppis 的观测 - I. 中心恒星的质量和候选行星的探测
DOI：
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
K. Ohnaka
中科院分区：
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作者：
P. Kervella;P. Kervella;W. Homan;A. Richards;L. Decin;I. McDonald;M. Montargès;K. Ohnaka
60亿年后，当太阳在渐近巨星分支（AGB）上演化时，它将从一个红巨星蜕变成一个美丽的行星状星云。这一壮观的演化将影响太阳系行星，但观测证实的演化模型的预测仍然是难以捉摸的，因为没有行星轨道的AGB星星尚未被发现。附近的AGB红巨星L2船尾座（d = 64 pc）被一个几乎是边对边的拱星尘埃盘所包围。我们报道了在波段7（ν ~ 350 GHz）用阿尔马在非常高的角分辨率（18 × 15 mas）下的新观测结果，这使我们能够分辨分子盘的速度分布。我们确定了尘埃盘中心空腔内的气体速度分布是开普勒型的，从而可以导出中心星星L2 Pup A的质量，mA = 0.659 ± 0.011 ± 0.041 M <$（± 6.6%）。从演化模型中，我们确定L2 Pup A具有接近太阳的主序星质量，因此是未来5至6 Gyr的太阳的相似物。连续谱图揭示了一个半径为2 Au单位的次级源（B），它贡献了AG B星星通量的f B / f A = 1.3 ± 0.1%。在径向速度v B = 12.2 ± 1.0km s-1的CO发射谱线中也检测到L2 Pup B.气体盘的旋转中心与AGB星星连续辐射的位置非常接近，这使我们能够将伴星的质量限制为m B = 12 ± 16 M Jup。L 2 Pup B极有可能是一颗行星或低质量的褐矮星，轨道周期约为5年。它的连续亮度和分子发射表明它可能被扩展的分子大气或吸积盘所包围。因此，L2 Pup成为我们太阳系遥远未来的一个有希望的Vantage位置。
Six billion years from now, while evolving on the asymptotic giant branch (AGB), the Sun will metamorphose from a red giant into a beautiful planetary nebula. This spectacular evolution will impact the solar system planets, but observational confirmations of the predictions of evolution models are still elusive as no planet orbiting an AGB star has yet been discovered. The nearby AGB red giant L 2 Puppis ( d = 64 pc) is surrounded by an almost edge-on circumstellar dust disk. We report new observations with ALMA at very high angular resolution (18 × 15 mas) in band 7 ( ν ≈ 350 GHz) that allow us to resolve the velocity profile of the molecular disk. We establish that the gas velocity profile is Keplerian within the central cavity of the dust disk, allowing us to derive the mass of the central star L 2 Pup A, m A = 0.659 ± 0.011 ± 0.041 M ⊙ (± 6.6%). From evolutionary models, we determine that L 2 Pup A had a near-solar main-sequence mass, and is therefore a close analog of the future Sun in 5 to 6 Gyr. The continuum map reveals a secondary source (B) at a radius of 2 AU contributing f B / f A = 1.3 ± 0.1% of the flux of the AGB star. L 2 Pup B is also detected in CO emission lines at a radial velocity of v B = 12.2 ± 1.0 km s -1 . The close coincidence of the center of rotation of the gaseous disk with the position of the continuum emission from the AGB star allows us to constrain the mass of the companion to m B = 12 ± 16 M Jup . L 2 Pup B is most likely a planet or low-mass brown dwarf with an orbital period of about five years. Its continuum brightness and molecular emission suggest that it may be surrounded by an extended molecular atmosphere or an accretion disk. L 2 Pup therefore emerges as a promising vantage point on the distant future of our solar system.