论文标题
旋转对大型恒星光谱可观察物的影响
The effects of rotation on massive star spectroscopic observables
论文作者
论文摘要
旋转在巨大的恒星中无处不在。旋转随着表面几何形状的变形而变形，这又导致了整个表面元素的表面重力，温度和电离平衡的参数分布改变。通常，在分析快速旋转巨星的光谱时会忽略这些3D效应。我们旨在确定忽略快速旋转产生的3D变形是否会影响最终的光谱可观察物，如果是的，则何种程度。使用垃圾邮件代码，我们生成一个合成光谱的网格，该网格解释了快速旋转的恒星的3D几何形状，并将它们与假设球形几何形状的合成光谱进行了比较。使用等效宽度和全宽度最大测量值作为代理，我们确定不同电离状态下单个线的测量温度，氦气丰度和预计的旋转速率如何随旋转速率和倾斜度而变化。我们发现3D几何形状可以对测得的参数产生重大影响。我们表明，温度高度依赖于旋转速率和倾斜度，并且在不同倾斜度下观察的相同系统的测量温度差异高达10 \％。我们还发现，氦丰度可以低估多达60 \％，并且不同电离状态的线可以在旋转速率上具有可测量的差异。我们证明，在观察到的数据中可以看到这些旋转速率的差异，并表明这可以使旋转速度独立倾斜度测量。我们的结果表明，忽略旋转的3D效应可能会在测得的光谱参数中引起明显的偏见，并且在许多情况下，测得的值远离真实值3 $σ$。
Rotation is ubiquitous among massive stars. With rotation comes a deformation to the surface geometry, which in turn leads to alterations in the distribution of parameters across the surface including surface gravity, temperature and ionization balance of surface elements. Often, these 3D effects are neglected when analyzing spectra of rapidly rotating massive stars. We aim to determine whether neglecting the 3D deformations resulting from rapid rotation has an impact on the final spectroscopic observables, and if so to what degree. Using the SPAMMS code, we generate a grid of synthetic spectra that account for the 3D geometry of rapidly rotating stars and compare them to synthetic spectra generated assuming spherical geometry. Using equivalent width and full width half maximum measurements as proxies, we determine how the measured temperature, helium abundance and projected rotation rates of individual lines in different ionization states vary with rotation rate and inclination. We find that the 3D geometry can have a significant impact on the measured parameters. We show that the temperature is highly dependent on both the rotation rate and the inclination, and that the same system viewed at different inclinations can have measured temperatures that differ by as much as 10\%. We also find that the helium abundance can be underestimated by as much as 60\%, and that lines in different ionization states can have measurable differences in rotation rates. We demonstrate that these differences in rotation rates can be seen in observed data and show that this could allow for an inclination independent measurement of the rotational velocity. Our results indicate that neglecting the 3D effects of rotation can cause significant biases in the measured spectroscopic parameters, and that in many cases, the measured values are more than 3$σ$ away from the true values.
