经典新星的$UBV$颜色演化。IV。爆发新星的时间拉伸$(U-B)_0$ - $(M_B-2.5\log f_{\rm s})$和$(V-I)_0$ - $(M_I-2.5\log f_{\rm s})$色量图
The $UBV$ Color Evolution of Classical Novae. IV. Time-Stretched $(U-B)_0$-$(M_B-2.5\log f_{\rm s})$ and $(V-I)_0$-$(M_I-2.5\log f_{\rm s})$ Color-Magnitude Diagrams of Novae in Outburst
摘要：
利用$t'=t/f_{\rm s}$对两颗经典新星的光变曲线和颜色演化进行适当的压缩和拉伸，可以得到两颗经典新星的光变曲线和颜色演化曲线的重叠。然后目标新星的亮度与模板新星的亮度通过$(M[t])_{\rm template} = (M[t/f_{\rm s}] - 2.5 \log f_{\rm s})_{\rm target}$相关，其中$M[t]$是绝对星等和时间的函数$t$，$f_{\rm s}$是目标新星和模板新星之间的时间尺度之比。在本系列的前几篇论文中，我们证明了许多新星在时间拉伸的$(B-V)_0$ - $(M_V-2.5 \log f_{\rm s})$色星等图中广泛重叠。在本文中，我们提出了另外两个$(U-B)_0$ - $(M_B-2.5\log f_{\rm s})$和$(V-I)_0$ - $(M_I-2.5\log f_{\rm s})$图，并表明它们的轨道重叠的16新星和52新星，分别。在这里，$(U-B)_0$、$(B-V)_0$和$(V-I)_0$是固有的$U-B$、$B-V$和$V-I$颜色，并且不被时间拉伸改变，并且$M_B$、$M_V$和$M_I$是绝对的$B$、$V$和$I$量值。使用这些属性，我们大大改善了以前的估计，他们的距离和红化。所得距离与{ \it Gaia}数据Release 2星表的距离基本一致。
英文摘要：
Light curves and color evolutions of two classical novae can be largely overlapped if we properly squeeze or stretch the timescale of a target nova against that of a template nova by $t'=t/f_{\rm s}$. Then the brightness of the target nova is related to the brightness of the template nova by $(M[t])_{\rm template} = (M[t/f_{\rm s}] - 2.5 \log f_{\rm s})_{\rm target}$, where $M[t]$ is the absolute magnitude and a function of time $t$, and $f_{\rm s}$ is the ratio of timescales between the target and template novae. In the previous papers of this series, we show that many novae broadly overlap in the time-stretched $(B-V)_0$-$(M_V-2.5 \log f_{\rm s})$ color-magnitude diagram. In the present paper, we propose two other $(U-B)_0$-$(M_B-2.5\log f_{\rm s})$ and $(V-I)_0$-$(M_I-2.5\log f_{\rm s})$ diagrams, and show that their tracks overlap for 16 novae and for 52 novae, respectively. Here, $(U-B)_0$, $(B-V)_0$, and $(V-I)_0$ are the intrinsic $U-B$, $B-V$, and $V-I$ colors and not changed by the time-stretch, and $M_B$, $M_V$, and $M_I$ are the absolute $B$, $V$, and $I$ magnitudes. Using these properties, we considerably refine the previous estimates of their distance and reddening. The obtained distances are in reasonable agreement with those of {\it Gaia} Data Release 2 catalogue.
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