GRS 1915+105的分层风几何：密度轮廓与半径
Stratified Wind Geometries of GRS 1915+105: Density Profiles and Radii
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中文总结 AI 辅助
该研究通过Chandra/HETG观测分析GRS 1915+105的风，利用AMD测量密度轮廓和半径，发现硬态密度反转和软态紧凑半径与慢速的普遍矛盾。
中文摘要 AI 辅助
低质量X射线双星GRS 1915+105展现出剧烈的光谱和通量变化，常伴随高度电离的外流。在本工作中，我们分析了跨越十多年的四次档案Chandra/HETG观测，这些观测的电离谱从软态（低内盘温度）到硬态（高内盘温度）变化很大。我们利用吸收测量分布（AMD，即柱密度随电离度的分布）这一深刻工具来测量风的性质。软态时期呈现出陡峭且单调上升的AMD，而硬态时期则在电离参数$\log\xi>3.3$处出现明显的转折。这是我们首次在外流中观察到负的AMD斜率，我们将其解释为局部的密度反转，这可能指向辐射压压缩区域。我们利用AMD形状和总柱密度测量来计算风的密度轮廓和距中心源的距离。对于硬态，我们在$10^{10}-10^{11}$ cm的半径处获得$10^{12}-10^{13}$ cm$^{-3}$的密度。这类测量通常无法通过X射线光谱直接实现。在这里，我们将外流的内半径和密度约束到两倍以内。软态中高达$\log\xi\sim6.5$的高$\xi$值且无转折，意味着更小的半径（约$10^8$ cm），这与观测到的慢速速度相矛盾。我们证明，这是恒星质量黑洞双星中高柱密度、高电离外流在紧凑发射半径与亚逃逸速度之间的普遍矛盾。
英文摘要
The low-mass X-ray binary GRS 1915+105 exhibits dramatic spectral and flux variability, often accompanied by highly ionized outflows. In this work, we analyze four archival Chandra/HETG observations spanning over a decade, which vary greatly in their ionizing spectrum from soft (low inner disk temperature) to hard (high inner disk temperature). We measure the wind properties, using the insightful tool of the absorption measure distribution (AMD, a distribution of column density with ionization). While the soft epoch reveals a steep, monotonically rising AMD, hard epochs feature a distinct turnover at high ionization parameter ($\logξ>3.3$). This is the first time we observe a negative AMD slope in an outflow, which we interpret as a localized density inversion, which could point to radiation-pressure compression zones. We utilize the AMD shape and total column density measurements to calculate the density profile and distance of the wind from the central source. For the hard states, we obtain densities of $10^{12}-10^{13}$ cm$^{-3}$ at radii of $10^{10}-10^{11}$ cm. Such measurements are usually not directly possible in X-ray spectroscopy. Here we constrain the inner radius and density of the outflow to a factor of two. The high-$ξ$ values up to $\logξ\sim6.5$ with no turnover in the soft state imply a smaller radius of a few $10^{8}$cm, which is in tension with the slow velocities observed. We demonstrate that this is a generic tension between compact launch radii and sub-escape velocities of high-column, high-ionization outflows observed in stellar-mass black hole binaries.
发表机构
- Technion（以色列理工学院）
- University of Michigan（密歇根大学）
- Villanova University（维拉诺瓦大学）
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