The Far-Ultraviolet "Continuum" in Protoplanetary Disk Systems II: CO Fourth Positive Emission and Absorption
Kevin France, Rebecca Schindhelm, Eric B. Burgh, Gregory J. Herczeg, Graham M. Harper, Alexander Brown, James C. Green, Jeffrey L. Linsky, Hao Yang, Hervé Abgra… 展开作者
Kevin France, Rebecca Schindhelm, Eric B. Burgh, Gregory J. Herczeg, Graham M. Harper, Alexander Brown, James C. Green, Jeffrey L. Linsky, Hao Yang, Hervé Abgrall, David R. Ardila, Edwin Bergin, Thomas Bethell, Joanna M. Brown, Nuria Calvet, Catherine Espaillat, Scott G. Gregory, Lynne A. Hillenbrand, Gaitee Hussain, Laura Ingleby, Christopher M. Johns-Krull, Evelyne Roueff, Jeff A. Valenti, Frederick M. Walter
We exploit the high sensitivity and moderate spectral resolution of the $HST$-Cosmic Origins Spectrograph to detect far-ultraviolet spectral features of carbon monoxide (CO) present in the inner regions of protoplanetary disks for the first time. We present spectra of the classical T Tauri stars HN Tau, RECX-11, and V4046 Sgr, representative of a range of CO radiative processes. HN Tau shows CO bands in absorption against the accretion continuum. We measure a CO column density and rotational excitation temperature of N(CO) = 2 +/- 1 $\times$ 10$^{17}$ cm$^{-2}$ and T_rot(CO) 500 +/- 200 K for the absorbing gas. We also detect CO A-X band emission in RECX-11 and V4046 Sgr, excited by ultraviolet line photons, predominantly HI LyA. All three objects show emission from CO bands at $λ$ $>$ 1560 Å, which may be excited by a combination of UV photons and collisions with non-thermal electrons. In previous observations these emission processes were not accounted for due to blending with emission from the accretion shock, collisionally excited H$_{2}$, and photo-excited H2; all of which appeared as a "continuum" whose components could not be separated. The CO emission spectrum is strongly dependent upon the shape of the incident stellar LyA emission profile. We find CO parameters in the range: N(CO) 10$^{18-19}$ cm$^{-2}$, T_{rot}(CO) > 300 K for the LyA-pumped emission. We combine these results with recent work on photo- and collisionally-excited H$_{2}$ emission, concluding that the observations of ultraviolet-emitting CO and H2 are consistent with a common spatial origin. We suggest that the CO/H2 ratio in the inner disk is ~1, a transition between the much lower interstellar value and the higher value observed in solar system comets today, a result that will require future observational and theoretical study to confirm.
From Protoplanetary Disks to Extrasolar Planets: Understanding the Life Cycle of Circumstellar Gas with Ultraviolet Spectroscopy
很少有科学发现像过去二十年中的系外行星科学爆炸那样吸引了公众的想象力。这项工作从根本上改变了我们对地球在宇宙中的地位的看法，并导致NASA对了解系外行星系统的人口统计及其形成条件进行了大量投资。系外行星系统的形成和演化的故事本质上是最初存在于原恒星环境中的星周气体和尘埃的故事;为了理解所观察到的行星系统的多样性，我们需要了解星周气体的生命周期，从其在原行星盘中的初始条件到其作为行星及其大气的终点。在这篇回应NASA信息请求的白皮书中，“下一个NASA紫外/可见光天体物理学任务概念的科学目标和要求（NNH 12 ZDA 008 L）”，我们描述了将使用未来NASA紫外（UV）/可见光空间天文台的独特能力来提高我们对星周气体生命周期的理解的科学计划。
Photoevaporation of Grain-Depleted Protoplanetary Disks around Intermediate-Mass Stars: Investigating Possibility of Gas-Rich Debris Disks as Protoplanetary Remnants
Ring Spacing from a Fourth-Order Radial Feedback Green Function in a Keplerian Accretion Disk
Tsung-Dao Lee Institute, Shanghai Jiao Tong University（上海交大李政道研究所）；School of Physics and Astronomy, Shanghai Jiao Tong University（上海交通大学物理与天文学院）；Institute of Science and Technology for Deep Space Exploration, Nanjing University（南京大学深空探测科学与技术研究院）
The Nature and Frequency of the Gas Outbursts in Comet 67P/Churyumov-Gerasimenko observed by the Alice Far-ultraviolet Spectrograph on Rosetta
爱丽丝是罗塞塔号上的一台远紫外成像摄谱仪，在多个目标中，它被设计用来观察67 P/丘留莫夫-格拉西缅科彗星彗发中各种原子和分子物种的发射。在2014年8月进入轨道后进行的初步观测显示，氢原子和氧原子的排放在空间上靠近原子核，并归因于H2O蒸汽的光电子碰撞解离。随后检测到来自原子碳的较弱的发射，并且也归因于CO2的电子碰撞解离，相对H I和C I线强度反映了CO2到H2O柱丰度沿着通过彗发的视线的变化。从2015年4月中旬开始，爱丽丝偶尔观察到一些爆发，其特征是在10-30分钟的时间内，原子发射突然增加，特别是半禁态的O I 1356多重态，而没有相应的长波长太阳反射光的增强。亮度比O I 1356/O I 1304的大幅增加表明O2是附加气体的主要来源。这些爆发与OSIRIS或导航相机拍摄的任何可见爆发图像都不相关。从2015年6月开始，爱丽丝光谱的性质发生了很大变化，连续观测到CO第四正带发射，随着指向而变化，但在时间上相当恒定。然而，CO似乎不是任何观察到的爆发的主要驱动力。
External Photoevaporation of the Solar Nebula II: Effects on Disk Structure and Evolution with Non-Uniform Turbulent Viscosity due to the Magnetorotational Instability
Molecules in the shadows of the protoplanetary disk HD 143006: Evidence for C/O $\gtrsim 1$ from simultaneously modeling fourteen ALMA lines
Space Research Institute, Austrian Academy of Sciences（奥地利科学院空间研究所）；Leibniz Institute for Astrophysics Potsdam (AIP)（波茨坦莱布尼茨天体物理研究所）；Space Research Organisation Netherlands（荷兰空间研究组织）；Department of Astronomy, University of Wisconsin-Madison（威斯康星大学麦迪逊分校天文学系）
利用 HD 143006 内盘投下的阴影，结合 ALMA 观测与 ProDiMo 模型，发现其外盘 C/O 略大于 1，并揭示慢热弛豫与紫外解吸对谱线形成的关键作用。
Revisiting the ultraviolet spectroscopy of the eta Tel edge-on debris disk
Exoplanets and Stellar Astrophysics Laboratory, NASA Goddard Space Flight Center（NASA戈达德太空飞行中心系外行星与恒星天体物理学实验室）；AlbaNova University Centre, Stockholm University（斯德哥尔摩大学阿尔巴诺瓦大学中心）；Universidad de Santiago de Chile（智利圣地亚哥大学）；Center for Interdisciplinary Research in Astrophysics and Space Exploration (CIRAS), Universidad de Santiago de Chile（智利圣地亚哥大学跨学科天体物理学与太空探索研究中心）；Millennium Nucleus on Young Exoplanets and their Moons (YEMS)（年轻系外行星及其卫星千年核心）；Department of Terrestrial Magnetism, Carnegie Institution for Science（卡内基科学学会地磁系）；Center for Astrophysics and Space Astronomy, University of Colorado（科罗拉多大学天体物理学与空间天文中心）；Eureka Scientific（尤里卡科学公司）
Far-ultraviolet flux distribution in Orion and its relation to stellar accretion
Trinity College Dublin, the University of Dublin（都柏林三一学院，都柏林大学）；Università degli Studi di Milano（米兰大学）；Queen Mary University of London（伦敦玛丽女王大学）；European Southern Observatory（欧洲南方天文台）；MaxPlanck Institute for Astronomy（马克斯·普朗克天体物理研究所）；Alma Mater Studiorum– Università di Bologna（博洛尼亚大学）；Universidad de Sevilla（塞维利亚大学）
