An Ejecta Kinematics Study of Kepler’s Supernova Remnant with High-resolution Chandra HETG Spectroscopy
An Ejecta Kinematics Study of Kepler’s Supernova Remnant with High-resolution Chandra HETG Spectroscopy
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DOI：
10.3847/1538-4357/ab7db1
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发表时间：
2019-05
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影响因子：
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通讯作者：
M. Millard;J. Bhalerao;Sangwook Park;Toshiki Sato;J. Hughes;P. Slane;D. Patnaude;D. Burrows-
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文献类型：
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作者：
M. Millard;J. Bhalerao;Sangwook Park;Toshiki Sato;J. Hughes;P. Slane;D. Patnaude;D. Burrows-
我们报告我们的体积径向速度的测量，从样品的小，富含金属的喷射物结在开普勒的超新星遗迹（SNR）。利用Chandra高能透射光栅光谱仪的观测结果，我们测量了这些结的谱中类氦Si Kα线心能量的多普勒频移，从而估算了它们的径向速度。我们估计这些喷出物结的高径向速度高达8000 km s-1。我们还根据2000年、2006年和2014年拍摄的钱德拉高级CCD成像光谱仪数据来测量样品的自行。我们测量的径向速度和自行表明，这些喷出物结的一些几乎是自由膨胀后，自爆炸后的2400年。移动最快的节显示出每年高达100.2 ″的自行。假设这些高速喷射物结在SNR的前向激波之前行进，我们估计到开普勒SNR的距离为4.4-7.5 kpc。我们发现，在我们的样本中，喷出物结的平均空间速度为vs. 4600 km s−1（距离为6 kpc）。我们注意到，从我们的样本中的15个喷出物结中有8个显示出统计上显著的（在90%的置信水平）红移光谱，相比之下，只有两个具有蓝移光谱。这可能表明开普勒的SNR中的喷出物分布不对称沿着视线;然而，需要更大的样本量来确认这一结果。
We report our measurements of the bulk radial velocity from a sample of small, metal-rich ejecta knots in Kepler’s supernova remnant (SNR). We measure the Doppler shift of the He-like Si Kα line-center energy in the spectra of these knots based on our Chandra High-Energy Transmission Grating Spectrometer observation to estimate their radial velocities. We estimate high radial velocities of up to ∼8000 km s−1 for some of these ejecta knots. We also measure proper motions for our sample based on the archival Chandra Advanced CCD Imaging Spectrometer data taken in 2000, 2006, and 2014. Our measured radial velocities and proper motions indicate that some of these ejecta knots are almost freely expanding after ∼400 yr since the explosion. The fastest moving knots show proper motions of up to ∼0.″2 per year. Assuming that these high-velocity ejecta knots are traveling ahead of the forward shock of the SNR, we estimate the distance to Kepler’s SNR d ∼ 4.4–7.5 kpc. We find that the ejecta knots in our sample have an average space velocity of vs ∼ 4600 km s−1 (at a distance of 6 kpc). We note that 8 of the 15 ejecta knots from our sample show a statistically significant (at the 90% confidence level) redshifted spectrum, compared to only two with a blueshifted spectrum. This may suggest an asymmetry in the ejecta distribution in Kepler’s SNR along the line of sight; however, a larger sample size is required to confirm this result.