X-Ray and Optical Study of Low Core Density Globular Cluster NGC6144 & E3

低核密度球狀星團NGC6144以及E3的X光與可見光波段之研究

藍仕豪(Shih-Hao Lan)

指導教授 ： 江國興

國立清華大學/理學院/天文研究所/碩士(2009年)

摘要

本篇論文將描述兩個低核密度球狀星團：NGC6144、以及E3的X光與可見光觀測及分析，並藉此討論其中X光源數量與球狀星團內，恆星經由遭遇生成雙星系統、以及原生雙星系統的關係。我們使用錢卓拉X光望遠鏡的觀測資料，經由CIAO軟體分析；以及使用哈伯太空望遠鏡尋找其可見光之對應物，並經由DOLPHOT軟體分析。在NGC614以及E3各自的半質量半徑內，我們分別偵測到NGC6144有六個X光源；而E3有三個X光源。然而在我們的觀測中，NGC6144估計將有4-5個X光源來自背景；E3則會有2個X光源來自背景，從統計上的結果，我們無法排除所有偵測到的光源皆不是來自背景。因為觀測時間與儀器敏感度，我們只會偵測到光度(在光子能量介於0.3-10千電子伏範圍內) 大於每秒 1.7×10^30 爾格的光源。經由分析，我們確定在NGC6144中有1-2組激變變星(CVs)及一組活躍雙星(ABs)；在E3中則有一組疑似激變變星。這些結果為原生雙星的重要證據。

關鍵字

球狀星團 ； NGC6144 ； E3 ； X光 ； 雙星系統 ； 激變變星

並列摘要

We report on the Chandra X-ray Observatory and Hubble Space Telescope observation of two low core density globular clusters, NGC6144 and E3. Within the half-mass radius and at a detection limit of L_X = 1.7 × 10^30 ergs/s , we found 6 X-ray sources in NGC6144, of which 4-5 are expected to be background sources; and 3 X-ray sources within the half-mass radius of E3, of which 2 are expected to be background sources. Therefore, we cannot exclude that all our sources are background sources. However, combining the results from X-ray and optical observations, we found that 1-2 sources in NGC6144 and 1 source in E3 are likely to be cataclysmic variables and that 1 source in NGC6144 is an active binary, based on the X-ray and optical properties. The number of faint X-ray sources in NGC6144 and E3 found with Chandra and HST is higher than a prediction based on collision frequency, but is closer to that based on mass. Our observations strongly suggest that the compact binary systems in NGC6144 and E3 are primordial in origin.

並列關鍵字

globular clusters ； NGC6144 ； E3 ； cataclysmic variables ； X-ray ； binaries

參考文獻

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