非常快速新星V1674天琴座壳层形成：超亮度起源
Formation of an optically thick shocked shell in the very fast nova V1674 Herculis: the origin of superbrightness
AI总结：
V1674天琴座的超亮度源于激波壳层的形成，其伽马射线峰值早于光学峰值，模型解释了这一现象。
摘要：
V1674天琴座是银河系中最快的（t2≈1天）经典新星，其绝对V峰值亮度M_V, max≈-10.2比典型快速新星亮一等。这种新星有时被称为超亮度新星。利用我们完全自洽的新星爆发模型结合1.35 M_太阳白矮星（WD）的光学厚风，其质量积累率为1×10^-11 M_太阳/年，我们澄清了在爆发后0.3天出现强反冲激波，刚好在白矮星光球最大膨胀之后。被激波冲击的壳层是光学厚的，以约3500 km/s的速度膨胀。当壳层膨胀到R_shell≈300 R_太阳时，其V亮度达到最大值M_V, max=-10.2，发生在第0.7天。之后，壳层转为光学薄，亮度低于新星风的自由自由发射。按时间顺序，自由自由发射的光学亮度在第0.3天达到最大值M_V=-9。然而，在第0.5-0.7天被光学厚的激波壳层约1等更亮的亮度所超越。GeV伽马射线流量在第0.4天达到最大值，因为伽马射线由第0.3天出现的激波发出。我们的模型一致解释了超亮度和伽马射线峰值明显早于光学V峰值的时间顺序。我们还为另一个超亮度新星V1500天琴座提供了类似的光变曲线模型。
英文摘要：
V1674 Her is the fastest ($t_2\sim 1$ day) classical nova in our Galaxy and its absolute $V$ peak of $M_{V,\rm max}\sim -10.2$ is one magnitude brighter than typical very fast novae. Such a nova is sometimes called a superbright nova. Using our fully self-consistent nova outburst model combined with the optically thick winds on a $1.35 ~M_\odot$ white dwarf (WD) with a mass accretion rate of $1\times 10^{-11} ~M_\odot$ yr$^{-1}$, we have clarified that a strong reverse shock arises $0.3$ days after the outburst, which is just after the maximum expansion of the WD photosphere. The shocked shell is optically thick and expanding with the velocity of $\sim 3500$ km~s$^{-1}$. Its $V$ brightness reaches maximum of $M_{V,\rm max}=-10.2$ when the shocked shell expands to $R_{\rm shell}\sim 300 ~R_\odot$ on day $\sim 0.7$. After that, the shocked shell turns to optically thin and becomes fainter than the brightness of free-free emission from the nova wind. In chronological order, the optical brightness of free-free emission reaches maximum of $M_V=-9$ on day 0.3. However, it is overtaken on day 0.5--0.7 by the $\sim$1 mag brighter luminosity of the optically thick shocked shell. The GeV gamma-ray flux reaches maximum on day 0.4 because the gamma-rays are emitted by the shock that arises on day 0.3. Our model consistently explains both the superbrightness and chronological order that the gamma-ray peak precedes substantially before the optical $V$ peak. We also present a similar light curve model for another superbright nova V1500 Cyg.
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