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Far-Ultraviolet Spectroscopy of the Circumstellar and Interstellar Environment of Young Stars.

机译：幼星的星际和星际环境的远紫外光谱。

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摘要

I have analyzed absorption from the CO Fourth Positive band system in the ultraviolet spectra of 6 Classical T Tauri stars, tripling the measurements in the literature. CO traces the molecular gas in the inner disk, providing constraints on the material in the planet-forming environment. I fit an absorption model in order to determine the column density and temperature of the gas in the disk. My CO rotational temperatures agree well with CO fluorescence measurements in the ultraviolet, but are in between infrared CO absorption and emission measurements.;I also fit absorption profiles of HI against the Lyman-alpha emission from a large sample of young stars (Classical T Tauri and Herbig Ae/Be) in order to determine the amount of interstellar extinction along the line of sight. Knowing the extinction value will allow us to reconstruct the intrinsic emission from the stars, which is the radiation impacting the protoplanetary disk. This radiation determines the thermal and chemical structure of the material that may form planets. I find lower visual extinction values than those in the literature using optical, infrared, and X-ray measurement techniques.;In addition, I have created a new technique using H2 fluorescence to empirically estimate the full ultraviolet extinction curve of young stars. I compare predicted line fluxes from my created H2 fluorescence model to observed fluxes from 7 strong progressions in order to determine the extinction over the 1100 - 1700 angstrom range. I then fit my extinction curves with models from the literature to determine best-fit Av and Rv values. I find that this technique is limited by the degeneracy between the Av and Rv values, needing one or the other to be determined independently. I hope to improve the technique and mitigate the limitations in future work.
机译：我已经分析了6颗经典T Tauri星的紫外光谱中来自CO第四正能带系统的吸收，是文献中测量值的三倍。 CO跟踪内盘中的分子气体，从而限制了行星形成环境中的物质。我拟合吸收模型以确定色谱柱中气体的柱密度和温度。我的CO旋转温度与紫外线中的CO荧光测量值非常吻合，但介于红外CO吸收和发射测量之间;我还拟合了HI对来自大量年轻恒星样本的Lyman-alpha发射的吸收曲线（经典T Tauri和Herbig Ae / Be），以确定沿视线的星际灭绝量。知道了消光值将使我们能够重建恒星的本征发射，这是影响原行星盘的辐射。这种辐射决定了可能形成行星的物质的热和化学结构。我发现使用光学，红外和X射线测量技术得出的视觉消光值低于文献中的值；此外，我还创建了一种使用H2荧光来凭经验估计年轻恒星的完整紫外线消光曲线的新技术。我将我创建的H2荧光模型的预测线通量与7个强过程中观察到的通量进行比较，以确定在1100-1700埃范围内的消光。然后，使用文献中的模型拟合消光曲线，以确定最佳拟合的Av和Rv值。我发现该技术受到Av和Rv值之间的简并性的限制，需要一个或另一个独立确定。我希望改进技术并减轻以后工作的局限性。

著录项

  • 作者

    McJunkin, Matthew.;

  • 作者单位

    University of Colorado at Boulder.;

  • 授予单位 University of Colorado at Boulder.;
  • 学科 Astrophysics.;Molecular physics.;Astronomy.
  • 学位 Ph.D.
  • 年度 2016
  • 页码 203 p.
  • 总页数 203
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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