吸积在近邻恒星和行星系统的形成和演化中的重要性

Our understanding of star and planet formation is founded upon following mass from the cloud into the star+disk system. The last step of formation is accretion from the disk onto the star. The disk-to-star accretion process determines how quickly the star gains its mass, drives powerful outflows that carry away angular momentum from the system, and produces energetic emission that leads to a complex photochemistry in the disk. In this proposal, I request funding to support a research program dedicated to measuring disk-star accretion from the earliest to the final stage of stellar birth to evaluate the effects of accretion history in the formation and evolution of stars and planetary mass objects. This program consists of several separate projects to be led by members of my group, including two PhD students. First, most of the stellar growth is thought to occur in the youngest protostellar phase, in large episodic outbursts driven by large disk instabilities, however to date the evidence for such outbursts in the Class 0 phase is largely indirect. We will use far-IR surveys of star forming regions to assess accretion variability as a test of episodic accretion models and to determine the optimal accretion history to implement into pre-main sequence evolutionary tracks. Second, we will measure accretion variability in classical T Tauri stars to probe disk instabilities and improve measurements of stellar ages. Finally, we are developing an innovative method for measuring accretion rates onto young planetary mass companions of solar mass stars, which will be used to test models for the formation and early evolution of these very low mass objects. These projects will significantly improve our understanding of accretion physics versus evolutionary state and object mass. The results will have important implications for models of how stars and planets evolve, for interpreting large unbiased photometric monitoring campaigns from LSST, GAIA, and fields in the proposed Kepler K2 program, and are a critical complement required to exploit the power of GAIA observations to measure ages and age spreads in young clusters.

我们对恒星及行星形成的理解主要基于物质如何从分子云转化为恒星＋盘系统。其中从盘到恒星表面的吸积决定了恒星质量增长的快慢。我们的课题是通过测量恒星形成中的吸积来判断吸积历史对其系统形成演化的影响。此项目包含多个单独课题。首先，恒星质量增长主要是在原恒星阶段由盘不稳定性触发的不定期爆发中完成。我们将利用恒星形成区的远红外数据来检测该爆发模型并完善主序前恒星的演化轨迹。其次，我们将测定典型金牛座T型星中的吸积变化性来研究盘的不稳定性，可提高恒星年龄测量的准确性。最后，我们正研究计算行星质量伴星吸积率的新方法来检测低质量星体的形成演化模型。这些课题对于认识吸积和恒星演化过程以及星体质量都有着极大意义。研究结果将会完善恒星和行星演化模型，对大型观测项目的消光和吸积过程的解释工作有所启发，同时它也是用于探索GAIA卫星在测量年轻星团年龄和恒星年龄分布之能力的关键性辅助工具。

本资助项目支持促进了我的小组开展有关恒星和行星形成、主序前恒星演化等课题的具有高度影响力的学术研究。这项资金作为小组的重要资助来源，在23篇引用达到357次的相关学术论文中（其中12篇由我的小组领导完成）被特别致谢。这些主要科学成就包括了在亚毫米波段开展的创新性研究，暨首次对原恒星的光度变化进行监测；通过使用高分辨率阿塔卡玛毫米/亚毫米波阵列望远镜（ALMA）观测恒星盘以辨识行星形成过程；以及开拓更完善地测量和理解主序前恒星演化过程的崭新方法。同时，该项资金支持了三篇博士学位论文（一篇已完成，一篇即将完成，一篇正在进行中），以及两名博士后研究员和数名本科生的科研项目。这项工作的首席研究员和合作研究员已经在诸多国内外学术会议以及特邀报告上展示了其工作成果。近几年来，作为我科研小组的唯一经费来源，这项基金在我们学术研究的开展、结果的发表和传播方面起到了至关重要的作用。