Spectral evolution of the nova V2468 Cygni: asymmetric and variable profiles of its emission lines
Spectral evolution of the nova V2468 Cygni: asymmetric and variable profiles of its emission lines
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nova V2468 Cygni 的光谱演化：其发射线的不对称和可变轮廓
DOI：
10.1051/0004-6361/201015448
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
H. Naito
中科院分区：
文献类型：
--
作者：
T. Iijima;H. Naito
从2008年3月发现天鹅座新星V2468 （nova Cyg 2008）到2009年底，意大利的阿齐亚戈天体物理天文台和日本兵库县的西harima天文台对其光谱演变进行了监测。这颗新星光谱的显著特点是其发射线的不对称和可变轮廓。在2008年的早期下降阶段，H I的排放在线曲线发生了变化，而在2009年它们的排放在线曲线基本稳定。另一方面，2009年观测到[O III]、[Fe VII]和He II的发射谱线变化很大。在2009年10月15日获得的光谱中，[O III]的发射线的红色部分相对于9月的轮廓增强，而He II和[Fe VII]的发射线的红色部分减弱。[Fe VII] 5721和[Fe VII] + [Ca V] 6087的发射谱线在2009年9月27日和28日呈现凸谱线，与其他谱线相似，而只有这些谱线在10月26日和29日呈现凹谱线。似乎很难用任何已知的新星壳模型来解释发射线剖面的变化。在最亮处的绝对星等和到新星的距离估计为M， v = -8.8±0.3等，d = 5.5±0.8 kpc。利用2009年9月观测到的He I、He I和He II谱线的强度，我们估计氦丰度的数量为N(He) = 0.20±0.01，喷出物的质量为1.7±1 × 10- 5 M⊙。在2009年7月21日获得的光谱中发现了一条非常宽的3790a到3850a的发射线。我们提出[Fe V] 3F、3839.3、3794.9、3851.3、3819.9等多行在当时突然加强，但这种现象的原因尚不清楚。
The spectral evolution of the classical nova V2468 Cygni (Nova Cyg 2008) was monitored at Asiago Astrophysical Observatory in Italy and at Nishi-Harima Astronomical Observatory in Hyogo Japan from soon after the discovery in March 2008 to the end of 2009. The notable peculiarities in the spectra of this nova were the asymmetric and variable profiles of its emission lines. The emission-line profiles of H I varied in the early decline stage in 2008, while their profiles were nearly stable in 2009. On the other hand, large variations in the profiles of the emission lines of [O III], [Fe VII], and He II were observed in 2009. In the spectrum obtained on 2009 October 15, the red parts of the emission lines of [O III] strengthened with respect to the profiles in September, while the red parts of the lines of He II and [Fe VII] faded. The emission lines of [Fe VII] 5721 and [Fe VII] + [Ca V] 6087 exhibited convex profiles on 2009 September 27 and 28 in a similar way to the other lines, while only these lines had concave profiles on October 26 and 29. It seems to be difficult to explain the variations in the emission-line profiles with any known model of nova shells. The absolute magnitude at light maximum and the distance to the nova are estimated to be M v = -8.8 ± 0.3 mag and d = 5.5 ± 0.8 kpc. Using the intensities of H I, He I, and He II lines observed in September 2009, we estimated the helium abundance in number to be N(He) = 0.20 ± 0.01, and the mass of the ejecta to be 1.7 ± 1 × 10- 5 M ⊙ . A very broad emission line from 3790 A to 3850 A was detected in the spectrum obtained on 2009 July 21. We propose that the multiple lines of [Fe V] 3F, 3839.3, 3794.9, 3851.3, 3819.9 etc. suddenly strengthened at that time, but the cause of this phenomenon is not known.