通过环双星盘观测到的主序前双星系统：KH 15D的新阶段
A Pre-Main Sequence Binary Viewed Through its Circumbinary Disk: A New Phase for KH 15D
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中文总结 AI 辅助
本研究分析KH 15D双星系统的测光数据，确定其修正后的测光周期，发现大振幅测光变异性时代结束，支持环双星盘后缘更透明的模型，为研究行星形成区提供观测阶段建议。
中文摘要 AI 辅助
双星T Tauri系统KH 15D在未来几年有望提供其环双星盘约3-5天文单位处气体与冰的前所未有的详细信息。我们首次分析了KH 15D系统的完整地面时间序列测光数据，其中2022年10月至2025年4月的数据此前从未被公开。通过结合最新的I波段数据与历史测量结果，我们发现大振幅测光变异性的时代已经结束。我们确定了修正后的测光周期P=48.365±0.005天，该周期可准确将75年时间跨度内的数据按相位对齐。我们采用恒星的星等与色指数来定义不同阶段，即1995-2008年恒星A或2010-2012年恒星B为系统非食外亮度的主要来源。我们首次假设存在灰色消光，测定了2002年至2025年期间系统的有效光学深度。当前系统非食外的色指数与两颗恒星的光组合结果一致，支持此前提出的环双星盘后缘比前缘更透明的模型。当恒星探测掩蔽物质时，我们在入凌和出凌阶段仍观测到“团块”和可变透明度的证据，并建议在这些阶段开展观测，以研究环双星盘中行星形成区的物理与化学性质。
英文摘要
The binary T Tauri system, KH 15D, is poised to provide unprecedented detail of gas and ices located between $\sim$3-5 AU of its circumbinary disk over the next few years. We analyze for the first time a complete set of ground-based time series photometry of the KH 15D system for which the 2022 October - 2025 April data have never been presented. By combining the latest $I$-band data with historical measurements, we show that the era of large amplitude photometric variability has ended. We define a revised photometric period of $P$ = 48.365 $\pm$ 0.005 days, which accurately phases data over a time span of seventy-five years. We adopt magnitudes and colors for the stars that define the epochs when either star A (1995-2008) or star B (2010-2012) is the primary source of the out-of-eclipse brightness of the system. We determine for the first time the effective optical depth for the system between 2002 and 2025 assuming gray extinction. The current out-of-eclipse system color is consistent with a combination of the light from both stars, supporting the previously suggested model in which the trailing edge of the circumbinary disk is more transparent than the leading edge. We continue to see evidence for ``clumps'' and variable transparency along ingress and egress when the stars are probing the occulting material and suggest that observations made during these phases should permit studies of the physical and chemical nature of the planet-forming zone with the circumbinary disk.
