臺灣博碩士論文加值系統

在低質量恆星形成過程中，磁場及其活動被認為扮演著重要的角色。被強烈認為是磁場活動產物的高能輻射也在低質量年輕恆星體周圍被偵測到。因此，2007年，Glassgold等人提出一價氖離子在12.81微米及二價氖離子在15.55微米的精細結構譜線能夠成為X-ray等高能輻射之追蹤方式。我們利用X-wind 模型來計算在一定範圍的質量逸散率及X-ray光度下，年輕恆星體之噴流所產生的精細結構譜線之通量及譜線的形狀。所有的譜線光度都與X-wind 模型中主要參數，質量逸散率，呈現良好的相關性，與X-ray光度，及各自譜線本身亦呈現良好的相關性。譜線的形狀寬且帶有強烈藍移的頂峰，其頂峰之速度接近噴流之終端速度。這樣的特徵提供了一個可測試的方向，來驗證氖之精細結構譜線及氧的禁制線產生自噴流。

Magnetic field and its activities are believed to play an important role in the low-mass star formation. High-energy radiations near the low-mass young stellar objects are detected and strongly believed to be the products of magnetic activities. The fine-structure transitions of NeII and NeIII at 12.81 and 15.55 is proposed to be the tracer of the high-energy radiation, X-ray by Glassgold et al. 2007. We use X-wind model of jets to calculate the flux and line shape of these lines for young stellar objects with a range of mass-loss rates and X-ray luminosities. All the line luminosities correlate well with the main parameter in the X-wind model, the mass-loss rate, and with the X-ray luminosity, and with one another. The line shapes are broad and have strong blue-shifted peaks near the effective terminal velocity of the jet. This characteristic provides a testable aspect of jet production of neon fine-structure lines and the OI forbidden transitions.

Contests

Acknowledgements i
Abstract (Chinese) ii
Abstract (English) iii
1 Introduction 1
2 Methodology 3
2.1 Young Stellar Objects …………………………………… 3
2.2 X-ray ………………………………………………………… 6
2.2.1 Observational evidences ………………………… 6
2.2.2 Theoretical simulation …………………………… 8
2.3 An Indicator of X-ray Ionization …………………… 11
2.3.1 Ionization of Neon atom ……………………… 11
2.3.2 Fine-structure of neon ions ………………… 15
2.4 A Reference Case ………………………………………… 18
3 Results 19
3.1 Physical Properties of the Reference Case ……… 19
3.2 Line Emission and the Correlation ………………… 26
3.3 Line Profiles …………………………………………… 35
4 Discussions 39
5 Conclusions 42
References 43

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