NEW CONSTRAINTS ON THE COOLING OF THE CENTRAL COMPACT OBJECT IN CAS A
NEW CONSTRAINTS ON THE COOLING OF THE CENTRAL COMPACT OBJECT IN CAS A
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DOI：
10.1088/0004-637x/779/2/186
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发表时间：
2013-11
期刊：
影响因子：
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通讯作者：
B. Posselt;G. Pavlov;V. Suleimanov;O. Kargaltsev
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文献类型：
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作者：
B. Posselt;G. Pavlov;V. Suleimanov;O. Kargaltsev
为了研究先前声称的Cas A超新星遗迹（SNR）中中央致密天体（CCO）的快速冷却，我们分析了两个钱德拉观测到的CCO，在一个最小化仪器光谱失真的设置中进行。我们用氢和碳中子星星大气模型拟合了2006年和2012年的两个CCO X射线光谱。两个历元之间5.5年内的温度和通量变化取决于对拟合参数的约束和有效面积校正的不确定性。如果我们允许改变等效发射区的大小，REm，有效温度基本上保持不变。如果REm保持恒定，则最佳拟合温度变化为负，但其统计显著性范围为0.8σ至2.5σ，具体取决于模型。如果我们假设2012年ACIS过滤器污染物的光学深度与其默认校准值相差±10%，则对于REm恒定的碳气氛，温度下降的显著性为0.8σ-3.1σ。因此，我们在数据中没有看到统计上显著的温度下降，但所涉及的不确定性太大，无法完全排除先前报道的快速冷却。我们的分析表明，在2006年和2012年之间，吸收通量在0.6-6 keV能量范围内减少了4%-6%（1.9σ-2.9σ显著性），在1.4-1.8 keV能量范围内最突出。这可能是由于探测器响应的未考虑变化或来自未分辨SNR材料沿沿着到CCO的视线的贡献引起的。
To examine the previously claimed fast cooling of the Central Compact Object (CCO) in the Cas A supernova remnant (SNR), we analyzed two Chandra observations of this CCO, taken in a setup minimizing instrumental spectral distortions. We fit the two CCO X-ray spectra from 2006 and 2012 with hydrogen and carbon neutron star atmosphere models. The temperature and flux changes in the 5.5 yr between the two epochs depend on the adopted constraints on the fitting parameters and the uncertainties of the effective area calibrations. If we allow a change of the equivalent emitting region size, REm, the effective temperature remains essentially the same. If REm is held constant, the best-fit temperature change is negative, but its statistical significance ranges from 0.8σ to 2.5σ, depending on the model. If we assume that the optical depth of the ACIS filter contaminant in 2012 was ±10% different from its default calibration value, the significance of the temperature drop becomes 0.8σ–3.1σ, for the carbon atmospheres with constant REm. Thus, we do not see a statistically significant temperature drop in our data, but the involved uncertainties are too large to firmly exclude the previously reported fast cooling. Our analysis indicate a decrease of 4%–6% (1.9σ–2.9σ significance) for the absorbed flux in the energy range 0.6–6 keV between 2006 and 2012, most prominent in the ≈1.4–1.8 keV energy range. It could be caused by unaccounted changes of the detector response or contributions from unresolved SNR material along the line of sight to the CCO.