X-Ray Line Profiles from Parameterized Emission within an Accelerating Stellar Wind
X-Ray Line Profiles from Parameterized Emission within an Accelerating Stellar Wind
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加速恒星风内参数化发射的 X 射线线轮廓
DOI：
10.1086/322413
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
Doron Cohen
中科院分区：
文献类型：
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作者：
S. Owocki;Doron Cohen
最近的探测XMM和钱德拉卫星的X射线线发射热，发光的恒星的动机，我们提出了合成线配置文件的参数化模型的热星风内发射的X射线。X射线谱线的发射发生在一个明确定义的同动坐标系共振波长处，该波长被一个由“β”速度定律v（r）= v∞（1 - R*/r）β参数化的恒星风外流多普勒频移。在X射线发射的某个初始起始半径Ro以上，假设发射填充因子的径向变化按半径f（r）~ r-q的幂律下降。计算出的发射廓线还考虑了风内的连续吸收，其总体强度由累积光学深度τ* 表征。根据以风终端速度v∞为单位的线中心的波长偏移，我们给出了参数β，τ*，q和Ro的各种组合的归一化X射线线轮廓，并且还包括仪器和/或宏观湍流加宽的影响，其特征在于具有参数化宽度σ的高斯。我们讨论了解释观测到的热星X射线光谱的影响，重点是区分“日冕”和“风震”的情况下签名。特别是，我们注意到，在迄今为止观察到的配置文件中，大量的发射线中心的longward将很难与预期的衰减风和恒星核心的风激波或日冕模型。
Motivated by recent detections by the XMM and Chandra satellites of X-ray line emission from hot, luminous stars, we present synthetic line profiles for X-rays emitted within parameterized models of a hot-star wind. The X-ray line emission is taken to occur at a sharply defined comoving-frame resonance wavelength, which is Doppler-shifted by a stellar wind outflow parameterized by a "β" velocity law, v(r) = v∞(1 - R*/r)β. Above some initial onset radius Ro for X-ray emission, the radial variation of the emission filling factor is assumed to decline as a power law in radius, f(r) ~ r-q. The computed emission profiles also account for continuum absorption within the wind, with the overall strength characterized by a cumulative optical depth τ*. In terms of a wavelength shift from line center scaled in units of the wind terminal speed v∞, we present normalized X-ray line profiles for various combinations of the parameters β, τ*, q, and Ro and also including the effect of instrumental and/or macroturbulent broadening as characterized by a Gaussian with a parameterized width σ. We discuss the implications for interpreting observed hot-star X-ray spectra, with emphasis on signatures for discriminating between "coronal" and "wind-shock" scenarios. In particular, we note that in profiles observed so far the substantial amount of emission longward of line center will be difficult to reconcile with the expected attenuation by the wind and stellar core in either a wind-shock or coronal model.