标题： 新星V382 Velorum 1999的X射线发射线光谱 显示英文标题

标题： An X-ray emission line spectrum of Nova V382 Velorum 1999

摘要： 我们报告了对经典新星V382 Vel（1999）的X射线光栅光谱的分析，该光谱是利用CHANDRA卫星上的LETG+HRC-S仪器获得的，显示发射线强于任何连续谱。检测到了Si、Mg、Ne、O、N和C的发射线，但未发现Fe的发射线。这些线的总亮度为4×10^27erg/s（修正了N_H=1.2×10^21cm^-2）。这些线具有宽轮廓，FWHM对应的速率为2900±200km/s。在轮廓中识别出了一些结构，但对于不同的元素，我们发现了不同的轮廓结构。虽然O的线显示出增宽的高斯轮廓，但Ne的线是双峰的，表明发射等离子体是碎片化的。利用发射度分布，我们推导出了相对元素丰度，并发现Ne和N的丰度相对于O有显著增强，而Fe并不过量。没有超过50Å的源发射以及OVIII Ly_alpha/Ly_beta线比值支持先前的氢柱密度值。我们在白矮星上发现了微弱的连续谱发射，与温度上限为T=3×10^5K的黑体谱一致，假设源半径为6000公里。集成黑体亮度的上限为2×10^36erg/s。BeppoSAX和Chandra ACIS对V382 Vel的观测显示，直到1999年12月30日，新星仍然明亮且处于超软相。我们的LETG观测是在6周后进行的，随后的所有X射线观测都显示了一个显著的衰减，几乎变为纯发射线阶段，这表明白矮星上的核燃烧在二月份已经停止。在没有光离化源的情况下，发射线是在碰撞电离和激发的膨胀壳层中形成的。 显示英文摘要

摘要： We report on the analysis of an X-ray grating spectrum of the Classical Nova V382 Vel (1999), obtained with the LETG+HRC-S instrument on board CHANDRA, which shows emission lines dominating over any continuum. Lines of Si, Mg, Ne, O, N, and C are identified, but no Fe lines are detected. The total luminosity in the lines is 4x10^27erg/s (corrected for N_H=1.2x10^21cm^-2). The lines have broad profiles with FWHM corresponding to a velocity 2900+-200km/s. Some structure is identified in the profiles, but for different elements we find different profile structures. While lines of O show a broadened Gaussian profile, those of Ne are double-peaked, suggesting a fragmented emitting plasma. Using the emission measure distribution we derive relative element abundances and find abundances of Ne and N that are significantly enhanced relative to that of O, while Fe is not over-abundant. The lack of any source emission longwards of 50A and the OVIII Ly_alpha/Ly_beta line ratio support previous values of the hydrogen column-density. We find weak continuum emission from the white dwarf, consistent with a black-body spectrum with an upper limit to the temperature of T=3x10^5K, assuming a source radius of 6000km. The upper limit for the integrated black-body luminosity is 2x10^36erg/s. The BeppoSAX and Chandra ACIS observations of V382 Vel show that the nova was bright and in the Super Soft phase as late as 1999 December 30. Our LETG observation obtained 6 weeks later, as well as all subsequent X-ray observations, showed a remarkable fading to a nearly pure emission line phase which suggests that nuclear burning on the white dwarf had turned off by February. In the absence of a photoionizing source the emission lines were formed in a collisionally ionized and excited expanding shell.