基于AstroSat观测的NS双星系统GX 349+2的光谱演化
Spectral evolution of NS binary system GX 349+2 using AstroSat observations
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中文总结 AI 辅助
利用AstroSat数据对Z源GX 349+2进行宽带光谱拟合，发现内盘半径保持截断且质量吸积率变化不足以解释Z轨迹，能量耗散主要发生在中子星边界层。
中文摘要 AI 辅助
我们利用AstroSat的LAXPC和SXT在2019年和2024年期间获得的观测数据，对Sco-like Z源GX 349+2进行了宽带光谱研究。X射线光变曲线表现出大幅度的变化，硬度-强度图描绘出特征性的Z形轨迹。利用硬度比和强度，Z形轨迹被划分为六个区域，包括正常分支、软顶点和一个延伸的耀发分支。我们在0.7-25.0 keV能量范围内，使用两种模型配置tbabs*(thcomp*bbodyrad+diskbb)和tbabs*(bbodyrad+thcomp*diskbb)进行同步宽带光谱拟合，以研究中子星边界层、吸积盘和康普顿化冕沿Z形轨迹的发射演化。比较分析表明，无论采用何种康普顿化几何结构，推断的内盘半径保持较大（约100 km），并且随着源光度增加，没有表现出系统的向内运动。这表明吸积盘保持截断状态，盘光度趋于饱和，与辐射压力影响的内盘一致。跨分支推断的质量吸积率变化相对较小，表明仅凭$\dot{M}$的变化无法解释观测到的Z形轨迹演化。相反，边界层成分在向耀发分支方向逐渐占主导地位，其温度和通量都随总光度增加而增加，而盘的相对贡献则减少。这些结果表明吸积功率向边界层及其相关的康普顿化区域重新分配，表明GX 349+2中的主要能量耗散发生在中子星的边界层区域内。
英文摘要
We present a broadband spectral study of the Sco-like Z source GX 349+2 using AstroSat LAXPC and SXT observations obtained during 2019 and 2024. The X-ray light curves exhibit large variability, and the hardness-intensity diagram traces the characteristic Z-shaped track. Using hardness ratio and intensity, the Z-track is segmented into six regions comprising normal branch, soft apex, and an extended flaring branch. We perform simultaneous broadband spectral fitting in the energy range 0.7-25.0 keV using two model configurations, tbabs*(thcomp*bbodyrad+diskbb) and tbabs*(bbodyrad+thcomp*diskbb), to study the evolution of emission from the neutron-star boundary layer, accretion disk, and Comptonizing corona along the Z-track. The comparative analysis reveals that, irrespective of the adopted Comptonization geometry, the inferred inner disk radius remains large (~100 km) and exhibits no systematic inward motion as the source luminosity increases. This suggests that the accretion disk remains truncated and the disk luminosity tends to saturate, consistent with a radiation pressure influenced inner disk. The relatively small variation in the inferred mass accretion rate across the branches indicates that changes in $\dot{M}$ alone cannot account for the observed Z-track evolution. Instead, the boundary-layer component becomes progressively dominant toward the flaring branch, with both its temperature and flux increasing with total luminosity, while the relative contribution from the disk decreases. These results indicate a redistribution of accretion power toward the boundary layer and the associated Comptonizing region, suggesting that the primary energy dissipation in GX 349+2 occurs within the boundary layer region of the neutron star.
发表机构
- Jamia Millia Islamia（贾米阿米利娅伊斯兰大学）
- Inter-University Centre for Astronomy and Astrophysics（大学间天文学与天体物理学中心）
- Tezpur University（特兹普尔大学）
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