原恒星FU Orionis可能并非在爆发：嵌入年轻偏心双星中的剧烈吸积抑制
The protostar FU Orionis may not be bursting: dramatic accretion suppression in embedded young eccentric binaries
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中文总结 AI 辅助
本研究通过星团形成模拟发现，FU Orionis等FUor爆发可能源于嵌入年轻偏心双星中近星点处的吸积抑制与BHL吸积爆发，而非持续爆发。
中文摘要 AI 辅助
1936年，原恒星FU Orionis开始变亮。两年后，其亮度增加了100倍，且此后未曾变暗。该天体定义了原恒星中FUor型吸积爆发的类别。以往模拟FUors的尝试模拟了孤立原恒星盘，从而限制了驱动爆发可用的质量并缩短了其持续时间。然而，这些原恒星嵌入在星际介质中，并通过吸积流从星际介质中主动吸积。本研究旨在从星际介质尺度出发探寻FUors的起源。我们对一个分辨率为25AU的星团形成模拟中的恒星粒子进行了无偏搜索，以寻找FUor候选体。大多数候选体是高度偏心双星中的低质量次星，正如FU Orionis。分辨率低至0.79AU的放大模拟发现，候选体在近星点处双星间距最小时经历剧烈的吸积抑制和爆发。接近近星点时，候选体的轨道速度变为超音速，剥离了附近的气体。经过近星点后，轨道速度降低，使得气体通过Bondi-Hoyle-Lyttleton（BHL）吸积迅速被候选体吸积。BHL吸积尾在候选体后方形成，并表现为吸积流。这种在近星点附近的剧烈抑制和爆发是嵌入年轻偏心双星中强烈变吸积的物理机制。该机制也意味着FU Orionis已恢复到其之前的吸积率。
英文摘要
In 1936, the protostar FU Orionis began to brighten. Two years later, it was 100 times brighter and has not dimmed since. This object defined the class of FUor-type accretion bursts in protostars. Previous attempts to model FUors simulate isolated protostellar discs, thereby limiting the mass available to drive the burst and shortening its duration. However, these protostars are embedded within the interstellar medium, from which they actively accrete via accretion streamers. This work seeks the origin of FUors starting at interstellar medium scales. An unbiased search of star particles from a 25AU resolution star cluster formation simulation was performed to find FUor candidates. Most candidates were low-mass secondary stars in highly eccentric binaries, like FU Orionis. Zoom-in simulations down to 0.79AU resolution found candidates experience dramatic accretion suppression and bursts at the closest binary separation at periastron. Approaching periastron, the candidate's orbital speed becomes supersonic striping away nearby gas. After periastron, the orbital speed decreases allowing gas to accrete onto the candidate rapidly via Bondi-Hoyle-Lyttleton (BHL) accretion. BHL accretion tails form behind the candidate and appear as accretion streamers. This dramatic suppression and burst near periastron is a physical mechanism for strong variable accretion in embedded young eccentric binaries. This mechanism also implies that FU Orionis returned to its former accretion rate.
发表机构
- Heidelberg Institute for Theoretical Studies（海德堡理论研究所）
- Research School of Astronomy & Astrophysics, Australian National University（澳大利亚国立大学天体物理与天文研究学院）
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