高质量Gamma-Ray双星1FGL周围SNR G284 .3 $-$ 1.8中的富镁喷出物J1018 .6 $-$ 5856
Magnesium-rich Ejecta in the SNR G284.3$-$1.8 Around the High-Mass Gamma-Ray Binary 1FGL J1018.6$-$5856
摘要：
我们目前的结果，从两个{ \it钱德拉}观测的16.6 d X射线/ $γ$射线高质量的二进制1FGL J1018.6 $-$ 5856位于中心的超新星遗迹G284.3 $-$ 1.8。在二元相位中分离0.25的二元光谱与两次观测的具有$Γ\approx1.7-1.8$的吸收幂律模型拟合（第二次观测期间的通量小1.7倍）。在高分辨率的ACIS-I图像中，我们发现了一个延伸发射$\approx2''$的暗示- $3''$东南的二进制，在$3σ$水平显着。双星演化代码再现了系统的观测属性，两颗大质量恒星的初始周期为18天，经历质量转移，留下一颗重$\approx2$ $\msun$中子星。在这种情况下，原始恒星的初始质量是27 $\pm 4$ $\msun$。残骸的\emph{Chandra}和{ \it XMM-Newton}图像显示它具有相对较低的X射线表面亮度。扩展X射线发射的两个最明亮的区域，其亮度为$d=5$ kpc的$\sim10^{33}$ erg s $^{-1}$，位于北部和西部，并显示出明显不同的光谱。北部的补丁是一致的冲击ISM，具有低温和长的电离时间尺度。然而，西部补丁主要是喷出物，并显示出显着增强镁含量相对于其他喷出物产品。推测的丰度比类似于大麦哲伦云遗迹N49 B。据我们所知，这只是在SNR中发现的第二种富含镁的喷出物。核心崩溃SNe的核合成模型预测富含镁的喷出物从非常大的$>25$ $\msun$祖。
英文摘要：
We present results from two {\it Chandra} observations of the 16.6 d X-ray/$γ$-ray high-mass binary 1FGL J1018.6$-$5856 located at the center of the supernova remnant G284.3$-$1.8. The binary spectra, separated by 0.25 in binary phase, are fit with an absorbed power-law model with $Γ\approx1.7-1.8$ for both observations (the flux during the second observation is a factor of 1.7 smaller). In the high-resolution ACIS-I image we found a hint of extended emission $\approx2''$--$3''$ southeast of the binary, significant at the $3σ$ level. Binary evolution codes reproduce the system's observed properties with two massive stars with an initial 18-day period, undergoing mass transfer and leaving behind a heavy $\approx2$ $\msun$ neutron star. The initial mass of the progenitor star in this scenario is 27 $\pm 4$ $\msun$. \emph{Chandra} and {\it XMM-Newton} images of the remnant show it has a relatively low X-ray surface brightness. The two brightest regions of extended X-ray emission, with luminosities $\sim10^{33}$ erg s$^{-1}$ for $d=5$ kpc, lie in the northern and western portions and show significantly different spectra. The northern patch is consistent with shocked ISM, with a low temperature and long ionization timescale. However, the western patch is dominated by ejecta, and shows significantly enhanced Mg content relative to other ejecta products. The abundance ratios inferred resemble those from the Large Magellanic Cloud remnant N49B. To our knowledge, this is only the second case of such Mg-rich ejecta found in an SNR. Nucleosynthesis models for core-collapse SNe predict Mg-rich ejecta from very massive progenitors of $>25$ $\msun$.
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