一颗非常明亮、高度熄灭、速度非常快的新星-- V1721天鹰座
A very luminous, highly extinguished, very fast nova - V1721 Aquilae
摘要：
快新星主要位于银河系平面内，慢新星则位于其凸起处。由于沿视线的高度星际消光，许多靠近飞机的新星都被错过了，只有最亮的才能看到。一颗非常靠近银河平面的新星是V1721天鹰座，在2008年9月22日的爆发中被发现。爆发后2.69天获得的光谱显示了非常高的膨胀速度（FWHM ~6450 km/s）。本文利用现有的爆发前后测光和爆发后谱学资料，认为该天体是一个非常快、明亮、高度熄灭的新星系统，平均抛射速度约为3400 km/s。2 MASS的爆发前近红外颜色表明，在静止时，该天体类似于许多静止的CNe，似乎有一个主序/次巨星次级，而不是巨星。根据新星的下降速度及其发射线轮廓，我们假设新星喷出物的轴比为~1.4，其倾角是这样的，中央双星吸积盘是面对观察者。吸积盘的蓝色贡献系统的近红外静止的颜色可能是显着的。新星喷出物的简单模型已被构造使用的形态建模代码XS 5，结果支持上述假设。由于低信噪比和高消光，该天体的光谱分类一直很困难，这消除了光谱内任何He/N或Fe II发射的所有证据。我们建议V1721 Aql的性质有两种可能性：它是一个U Sco型RN，有一个次巨星次级，或者，不太可能，它是一个高能量的明亮和快速的经典新星，有一个主序星次级。未来监测对象可能的RN事件可能是值得的，因为将档案搜索以前的爆发。
英文摘要：
Fast novae are primarily located within the plane of the Galaxy, slow novae are found within its bulge. Because of high interstellar extinction along the line of sight many novae lying close to the plane are missed and only the brightest seen. One nova lying very close to the Galactic plane is V1721 Aquilae, discovered in outburst on 2008 September 22. Spectra obtained 2.69 days after outburst revealed very high expansion velocities (FWHM ~6450 km/s). In this paper we have used available pre- and post-outburst photometry and post-outburst spectroscopy to conclude that the object is a very fast, luminous, and highly extinguished A_V=11.6+/-0.2) nova system with an average ejection velocity of ~3400 km/s. Pre-outburst near-IR colours from 2MASS indicate that at quiescence the object is similar to many quiescent CNe and appears to have a main sequence/sub-giant secondary rather than a giant. Based on the speed of decline of the nova and its emission line profiles we hypothesise that the axis ratio of the nova ejecta is ~1.4 and that its inclination is such that the central binary accretion disc is face-on to the observer. The accretion disc's blue contribution to the system's near-IR quiescent colours may be significant. Simple models of the nova ejecta have been constructed using the morphological modelling code XS5, and the results support the above hypothesis. Spectral classification of this object has been difficult owing to low S/N levels and high extinction, which has eliminated all evidence of any He/N or FeII emission within the spectra. We suggest two possibilities for the nature of V1721 Aql: that it is a U Sco type RN with a sub-giant secondary or, less likely, that it is a highly energetic bright and fast classical nova with a main sequence secondary. Future monitoring of the object for possible RN episodes may be worthwhile, as would archival searches for previous outbursts.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
