DIAGNOSTIC LINE EMISSION FROM EXTREME ULTRAVIOLET AND X-RAY-ILLUMINATED DISKS AND SHOCKS AROUND LOW-MASS STARS
DIAGNOSTIC LINE EMISSION FROM EXTREME ULTRAVIOLET AND X-RAY-ILLUMINATED DISKS AND SHOCKS AROUND LOW-MASS STARS
复制标题
来自极紫外线和 X 射线照射的圆盘以及低质量恒星周围激波的诊断线发射
DOI：
10.1088/0004-637x/703/2/1203
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
U. Gorti
中科院分区：
文献类型：
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作者：
D. Hollenbach;U. Gorti
极紫外线（EUV; 0.1-2 keV波段的X射线可以将年轻的低质量恒星周围的盘表面加热到数千度，并将电离势大于13.6 eV的物质加热到数千度。由原恒星风产生的冲击也可以加热和加热靠近星星/盘系统的同一物种。这些过程产生诊断线（例如，[Ne ii] 12.8 μm和[O i] 6300 μ m），我们将其建模为关键参数的函数，如EUV光度和光谱形状，X射线光度和光谱形状，以及风质量损失率和激波速度。将我们的模型与观测结果进行比较，我们得出结论，无论是在风中的内部冲击还是入射到磁盘表面的X射线，通常都会产生所观察到的[Ne ii]线，尽管在某些情况下EUV可能占主导地位。由风与盘的斜向相互作用产生的激波不太可能是[Ne ii]源，因为这些激波太弱，不可能是Ne源。即使[Ne ii]主要是由X射线或内部风激波产生的，氖的观测通常将这些年轻低质量恒星的EUV光子光度上限定为1042 s−1。观测到的[O i] 6300线既有低速分量（LVC），又有高速分量。后者可能是由内部风震引起的。对于前者，我们发现，X射线可能产生更多的[O i]亮度比EUV层，EUV和X射线层之间的过渡层，或剪切层的原恒星风的冲击和夹带盘材料在径向流在整个磁盘的表面。我们的软X射线模型产生了亮度高达10−4 L的[O i] LVC，但可能无法解释最明亮的LVC。
Extreme ultraviolet (EUV; 13.6 eV <hν ≲ 100 eV) and X-rays in the 0.1–2 keV band can heat the surfaces of disks around young, low-mass stars to thousands of degrees and ionize species with ionization potentials greater than 13.6 eV. Shocks generated by protostellar winds can also heat and ionize the same species close to the star/disk system. These processes produce diagnostic lines (e.g., [Ne ii] 12.8 μm and [O i] 6300 Å) that we model as functions of key parameters such as EUV luminosity and spectral shape, X-ray luminosity and spectral shape, and wind mass loss rate and shock speed. Comparing our models with observations, we conclude that either internal shocks in the winds or X-rays incident on the disk surfaces often produce the observed [Ne ii] line, although there are cases where EUV may dominate. Shocks created by the oblique interaction of winds with disks are unlikely [Ne ii] sources because these shocks are too weak to ionize Ne. Even if [Ne ii] is mainly produced by X-rays or internal wind shocks, the neon observations typically place upper limits of ≲1042 s−1 on the EUV photon luminosity of these young low-mass stars. The observed [O i] 6300 Å line has both a low velocity component (LVC) and a high velocity component. The latter likely arises in internal wind shocks. For the former we find that X-rays likely produce more [O i] luminosity than either the EUV layer, the transition layer between the EUV and X-ray layer, or the shear layer where the protostellar wind shocks and entrains disk material in a radial flow across the surface of the disk. Our soft X-ray models produce [O i] LVCs with luminosities up to 10−4 L☉, but may not be able to explain the most luminous LVCs.
X 射线照射的原行星盘大气。
DOI：
10.1088/0004-637x/699/2/1639
发表时间：
2009
期刊：
The Astrophysical Journal
影响因子：
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作者：
Ercolano B
通讯作者：
Ercolano B