海山二的历史光变曲线：来自主星的周期性洛希瓣渗溢证据
Eta Carinae's historical light curve: evidence for cyclic Roche lobe overflow from the primary star
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中文总结 AI 辅助
本研究利用HST观测校准地基光度数据，分离海山二恒星核心与星云的V波段流量，发现大振幅轨道光变曲线，证实主星存在周期性洛希瓣渗溢，并解释了相关光度特征的成因。
中文摘要 AI 辅助
自1940年以来获取的大量海山二（$η$ Carinae）地基光度测量数据，因恒星核心与周围星周星云的流量混合，一直难以进行定量建模。在哈勃空间望远镜时代，空间分辨成像与分光光度测量实现了这些成分的分离，使得从地基观测中恢复恒星核心的$V$波段亮度成为可能。我们利用1999—2020年的HST（ACS和STIS）观测数据，分离出恒星核心与星云的$V$波段流量，并以此校准同期的地基光度测量数据。主要发现是一条振幅为$Δm \approx \pm 0.2$星等的轨道光变曲线，其振幅比主星椭球形变模型预测的高出数倍。观测表明，洛希瓣渗溢始于近星点前$-75$天，与轨道光变曲线的上升起始时间重合，且持续150天。一团不断膨胀（随后消散）的气体云反射主星的光线，能够解释观测到的轨道光变曲线大振幅。在近星点前约$-18$天会出现一个尖锐的周期性光度峰，随后在伴星上合附近（T$_0+5.2$天）出现一个宽谷，我们将其解释为抛射物质的部分食，这一现象与X射线中的“浅谷”重合，而后者也被归因于食效应。
英文摘要
The large amount of ground-based photometric measurements of $η$ Carinae obtained since 1940 have remained problematic for quantitative modeling due to the blending of flux from the stellar core and the surrounding circumstellar nebula. In the era of the Hubble Space Telescope, spatially resolved imaging & spectrophotometry have enabled disentanglement of these components, allowing recovery of the stellar core $V$-band brightness from ground-based observations. We isolate the $V$-band fluxes of the stellar core and nebula using 1999--2020 HST (ACS and STIS) observations, and use these to calibrate coeval ground-based photometry. The main finding is an orbital light curve with an amplitude $Δm \approx \pm 0.2\,$mag, many times higher than that modeled by ellipsoidal deformation of the primary. The observations suggest that Roche lobe overflow starts at $- 75$ days before periastron in coincidence with the start of rising in the orbital light curve, and remains for 150 days. An expanding (and afterwards dissipating) gas cloud reflecting the light from the primary would explain the observed large amplitude of the orbital light curve. A sharp periodic photometric peak occurs at $\sim -18$ days from the periastron. It is followed by a broad minimum around the superior conjunction of the secondary (T$_0+5.2$ days), which we interpret as a partial eclipse of the ejected material, in coincidence with the \emph{shallow minimum} in X-rays, which also has been attributed to an eclipse.
