FG Sge：2019年新的太阳能测光和短期尘壳清除
FG Sge: new multicolor photometry and short-term dust shell clearing in 2019
摘要：
我们提出了一个新阶段的长期测光研究的FG Sge，这是一个快速发展的中心恒星的行星状星云母鸡1-5。我们在2008-2021年和2013-2021年分别在光学（$BVR_CI_C$）和红外（IR）（$JHKLM$）区域对SAI MSU望远镜进行的新观测使我们能够追踪近年来恒星亮度的演变。最重要的观测是在2019年进行的，当时这颗恒星经历了短暂的尘埃壳清理，并在$BVR_C$中可见。根据FG Sge在0.4-5 $μ$ m波长范围内的光谱能量分布，导出了尘埃壳层参数：尘埃颗粒尺寸$a=0.01μ$ m，内半径温度$T_{\text{dust}}=900$ K，光学厚度$τ(K)=0.5$（$τ(V)=4.5$），尘埃总质量$M_{\text{dust}}=7\cdot10^{-5} M_{\odot}$。在2019年尘埃壳的短期清理之后，另一个尘埃结构被喷射出来，导致恒星在所有观测到的波段中衰落。根据红外亮度和颜色曲线，我们估计了2019-2020年的尘埃深度增长。
英文摘要：
We present the results of a new stage of the long-term photometric study of FG Sge which is a quickly evolving central star of the planetary nebula Hen 1-5. Our new observations carried out on the SAI MSU telescopes in the optical ($BVR_CI_C$) and infrared (IR) ($JHKLM$) regions in 2008-2021 and 2013-2021, respectively, allowed us to trace the evolution of the star's brightness in recent years. The most significant observations were performed in 2019 when the star suffered a short clearing of the dust shell and became visible in $BVR_C$. Based on the spectral energy distribution of FG Sge in the 0.4-5 $μ$m wavelength range we derived the dust shell parameters: the size of dust grains $a=0.01μ$m, the inner radius temperature $T_{\text{dust}}=900$ K, optical depth $τ(K)=0.5$ ($τ(V)=4.5$), the total mass of dust $M_{\text{dust}}=7\cdot10^{-5} M_{\odot}$. After the short-term clearing of the dust shell in 2019, another dust structure was ejected that resulted in the star fading in all the observed bands. Based on the IR brightness and color curves, we estimated the dust depth growth in 2019-2020.
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