Spectral evolution of Nova (V1494) Aql and its high velocity jets
Spectral evolution of Nova (V1494) Aql and its high velocity jets
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Nova (V1494) Aql 及其高速射流的光谱演化
DOI：
10.1051/0004-6361:20030528
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发表时间：
2003
影响因子：
6.5
通讯作者：
H. Esenoğlu
中科院分区：
文献类型：
--
作者：
T. Iijima;H. Esenoğlu
在1999年12月至2000年9月发现快速新星V1494 Aql后不久，对它的光谱演化进行了监测。第一个光谱显示出突出的H I和Fe II的发射线，而He I被认为是在吸收。H I、He I和N II的吸收分量的径向速度在下降初期迅速增加（负向），而Fe II的径向速度几乎保持不变。当2000年2月6日在季节性中断后拍摄到新的光谱时，这颗新星正处于过渡阶段。过渡阶段的光谱显示出H I、He I、He II、N II、N III、Si II、（N II）、（O I）、（O III）、（Fe II）、（Fe VI）、（Ca V）等发射线，因此Fe Ⅱ的发射谱线消失了。2000年2月至4月中旬，在V波段观测到了一个时间尺度约为16：51天，平均振幅约为1.2等的光度准周期振荡。He Ⅱ和（Ca V）的发射线在振荡的最大值附近消失，而N Ⅱ和N Ⅲ的发射线增强。与此同时，高速（2900和+2830公里秒-1）宽发射翼的H-I线出现，这表明喷射高速射流。整个星云阶段的兴奋状态增加。2000年9月拍摄的最后一个光谱显示出高度激发的发射线，高达（Fe VII）和（Fe X）6374.5。由Na I D1和D2的星际吸收分量的等效宽度估计星际消光为E（B V）= 0：6 0：1。利用这个结果，到新星的距离估计为1：6 0：2 kpc。结果表明，喷出物的质量和氦丰度分别为6：2 1：4 10 5 M和N（He）/N（H）= 0：13 0：0 1。在星云阶段，喷出物的电子密度以Ne /t0：8的比例下降，其中t是从光最大值开始的时间。这种低的下降率表明，喷出物有一个环形的形状，以及一个大的质量损失，可能一直持续到整个星云阶段。
Spectral evolution of the fast nova V1494 Aql was monitored soon after its discovery in December 1999 to September 2000. The first spectra showed prominent emission lines of H I and Fe II, while He I was seen in absorption. The radial velocities of the absorption components of H I, He I and N II rapidly increased (in the negative sense) during the early decline stage, while those of Fe II remained nearly constant. When a new spectrum was taken on February 6, 2000 after the seasonal interruption, this nova was in the transition stage. The spectra in the transition stage showed emission lines of H I, He I, He II, N II, N III, Si II, (N II), (O I), (O III), (Fe II), (Fe VI), (Ca V) etc., hence the emission lines of Fe II had disappeared. A quasi-periodic oscillation of luminosity with a time scale of about 16:5 1 days and a mean amplitude of about 1.2 mag in V band was seen from February to the middle of April 2000. The emission lines of He II and (Ca V) disappeared around a light maximum of the oscillation, while the emission lines of N II and N III strengthened. At the same time high velocity ( 2900 and+2830 km s 1 ) broad emission wings of H I lines appeared, which suggest an ejection of high velocity jets. The excitation state increased throughout the nebular stage. The last spectra taken in September 2000 showed highly excited emission lines up to (Fe VII) and (Fe X)6374.5. The interstellar extinction is estimated as E(B V) = 0:6 0:1 from the equivalent widths of the interstellar absorption components of Na I D1 and D2. Using this result, the distance to the nova is estimated as 1:6 0:2 kpc. The mass and the helium abundance of the ejecta are estimated as 6:2 1:4 10 5 M and N(He)/N(H)= 0:13 0:01, respectively. The electron density of the ejecta decreased as Ne / t 0:8 during the nebular stage, where t is time from light maximum. This low decline rate suggests that the ejecta had a ring like shape as well a large mass loss which may have continued throughout the nebular stage.