AI 中文总结
本研究针对近邻超大质量星团Westerlund 1，利用钱德拉ACIS-I观测数据分离点源后分析其弥散X射线辐射，揭示了不同区域的辐射机制及星团风性质，为恒星反馈研究提供了关键观测依据。
AI 中文摘要
Westerlund 1（Wd 1）是距离太阳最近的超大质量星团，拥有超过10万颗各类光谱型的恒星，质量范围延伸至褐矮星。这些恒星强烈加热周围的星际介质（ISM），使Wd 1成为研究恒星对星团内气体反馈的关键场所。我们开展了迄今为止对其弥散辐射最详细的X射线研究，旨在分离并量化点源对真实弥散辐射的贡献。我们分析了8×8角分视场内的36次钱德拉（Chandra）ACIS-I观测数据。通过ACIS Extract工具，利用与能量相关的点扩散函数（PSF）模型和自适应99% enclosed-energy掩模，去除了4922个点源；随后减去PSF翼污染并校正背景，再在软、中、硬波段应用自适应平滑处理。光谱拟合显示，弥散X射线与大质量恒星在空间上相关，核心区域（2号区域）符合APEC+PSHOCK模型，温度为1.81±0.24 keV和4.11±1.98 keV，并存在6.7 keV的铁Kα线；外围1号区域呈现电荷交换（CXE）发射，符合CXE+NEI模型，温度更软，为0.27±0.04 keV和1.09±0.05 keV。柱密度范围为1.84-2.24×10²² cm⁻²，0.5-8.0 keV波段的总弥散光度约为9.6(±0.3)×10³³ erg/s。核心附近的硬辐射可能来自热化为沃尔夫-拉叶星（Wolf-Rayet）星风及星风碰撞，经绝热膨胀和与较冷ISM的湍流混合后变软；软成分延伸得更远，可能来自消光较低区域的CXE，未发现非热贡献。星团风模型预测的光度比观测值高约2.2倍，与低密度、部分排空的星团内介质一致；得到的风- X射线效率η约为4.3×10⁻⁶，比天鹅座OB2低约两个数量级，因此产生的弥散X射线辐射相对较暗。
英文摘要
Westerlund 1 (Wd 1) is the closest supermassive star cluster to the Sun, with over 100,000 stars of all spectral types down to brown dwarfs. This population strongly heats the surrounding interstellar medium (ISM), making Wd 1 a key site to study stellar feedback on intracluster gas. We present the most detailed X-ray study to date of its diffuse emission, aiming to separate and quantify the point-source contribution to the true diffuse emission. We analysed 36 Chandra ACIS-I observations within an 8x8 arcmin window. After removing 4922 point sources with ACIS Extract using energy-dependent PSF models and adaptive 99% enclosed-energy masks, we subtracted PSF-wing contamination and corrected for background, then applied adaptive smoothing in soft, medium, and hard bands. Spectral fitting suggests a shocked thermal plasma, with diffuse X-rays correlating spatially with massive stars. The core (Region #2) fits an APEC+PSHOCK model, with temperatures of 1.81+/-0.24 and 4.11+/-1.98 keV and a 6.7 keV Fe K-alpha line. The outer Region #1 shows charge-exchange emission, fitting a CXE+NEI model with softer temperatures of 0.27+/-0.04 and 1.09+/-0.05 keV. Column densities range from 1.84-2.24x10^22 cm^-2, and the total (0.5-8.0 keV) diffuse luminosity is ~9.6(+/-0.3)x10^33 erg/s. Near the core, hard emission likely arises from thermalised Wolf-Rayet winds and wind-wind collisions, softened by adiabatic expansion and turbulent mixing with cooler ISM. The soft component extends farther out, possibly from CXE in lower-extinction regions. No non-thermal contribution is found. A cluster-wind model predicts a luminosity ~2.2 above that observed, consistent with a low-density, partially evacuated intracluster medium. The resulting wind-to-X-ray efficiency, eta ~4.3x10^-6, is about two orders of magnitude below Cygnus OB2, yielding comparatively subluminous diffuse X-ray emission.
