Solving the Ubiquitous Problem of Stellar Radii
Solving the Ubiquitous Problem of Stellar Radii
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发表时间：
2020-03
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通讯作者：
S. Morrell
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作者：
S. Morrell
第一督导：蒂姆·奈勒教授第二督导：大卫·辛教授这篇论文将解决测量恒星半径的问题，这是现代天体物理学中许多领域普遍存在的问题。介绍了一种技术，它结合恒星光谱能量分布(SED)下的面积来测量它的光度，并结合SED的形状来测量它的温度，从它的半径开始。这种方法解决了现有方法面临的许多问题，我们回顾了这些方法，因为它提供了仅使用多波段光度和精密视差来精确测量恒星半径的方法。众所周知，无论是在前主序(Pre-MS)上，还是在主序(MS)上，模型给出的M-矮星的半径和温度与观测结果都不一致。这种方法被应用于昂宿星团和普雷塞普星团中的前MS M-矮星，以执行与恒星内部预测的半径的直接比较。对恒星大气模型的物理性和准确性的评估也是通过将它们产生的合成光谱与通量校准的光谱观测进行比较来进行的。合成光谱的参数由SED拟合提供，允许执行方法本身的验证。Gaia DR2的出现意味着现在可以对M矮星进行可靠的距离测量，这使得这项研究得以扩展到Tom恒星。通过这一研究，研究了MSM-Dwarff中半径膨胀作为质量函数的性质。这一点至关重要，有助于洞察观察到的半径膨胀背后的物理原理，从而对当前支撑半径膨胀的理论进行批判性评估。这项研究的结论是，磁场模型目前无法解释M-矮星的半径膨胀。鉴于SED拟合方法在测量各种场星的恒星半径方面的成功应用，这项工作的基础是解决以下问题
1st Supervisor: Professor Tim Naylor 2nd Supervisor: Professor David Sing This thesis will address the problem of measuring stellar radii, which is ubiquitous across many fields of modern astrophysics. A technique is introduced which integrates the area beneath the stellar spectral energy distribution (SED) of a star to measure its luminosity, and the shape of the SED to measure its temperature from which follows its radius. This method addresses many of the problems facing of existing methods, which are reviewed, as it provides accuratemeasurements of stellar radius using onlymultiband photometry and precision parallaxes. It is well known that the radii and temperatures of M-dwarf prescribed by models are in disagreement with observations, both on the pre-main-sequence (pre-MS) and the main-sequence (MS). This methodology is applied to pre-MS M-dwarfs in the Pleiades and Praesepe clusters to perform a direct comparison to the radii predicted by stellar interiors. Assessment of the physicality and accuracy of the stellar atmosphere models is also performed by comparing synthetic spectra generated from them to flux–calibrated spectroscopic observations. The parameters for the synthetic spectra are provided by the SED fitting, allowing verification of the methodology itself to be performed. The advent of Gaia DR2 means that reliable distances are now available for field M-dwarfs, permitting the extension of this investigation toMS stars. Through this investigation, the nature of radius inflation inMSM-dwarfs is studied as a function ofmass. This crucially allows insight into the physics behind the observed radius inflation, allowing current theories underpinning radius inflation to be critically assessed. The conclusion of this investigation is that magnetic models are currently unable to explain radius inflation in M-dwarfs. Given the successful application of the SED fitting methodology in measuring the stellar radii of miscellaneous field stars, this work is built upon to address the problem of