发表机构
Ariel University; Technion - Israel Institute of Technology（阿里埃勒大学; 以色列理工学院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文观测船底座η星2025.6 X射线极小期，发现其提前约10天，并证实X射线下降源于恒星风不稳定性及主星风吸积到次星，而非视线吸收，且吸积可能驱动喷流。
AI 中文摘要
我们展示了近期2025.6 X射线极小期及船底座η星恢复的观测结果，这些观测由NICER/XTI、Swift/XRT、XRISM/Xtend和Chandra/HRC-I获得。我们构建了软（0.5–2 keV）和硬（2–10 keV）波段的 light curves（光变曲线），并推导了硬度比。X射线发射达到极小值的时间比前五个周期早了约10天。与之前的事件一样，光谱在下降期间变软，而X射线光度在短时间尺度上发生变化。这些发现强化了以下结论：增强的视线方向吸收（例如日食期间预期的那种吸收）在产生光谱事件中并不起重要作用。相反，它们表明X射线的下降是由两颗恒星风及其相互作用中的随机变化和不稳定性、碰撞风区的破坏以及主星风吸积到次星上引起的。近星点附近深X射线极小期背后的主要过程是主星损失的质量吸积到次星上。船底座η星近星点经过时的吸积意味着，在十九世纪的大爆发和小爆发期间，当主星以高得多的速率损失质量时，吸积以高得多的速率发生。这种吸积很可能发射喷流。更广泛的意义在于，双星系统中的吸积事件（可能伴随喷流发射）为其他亮蓝变星巨爆发和中等光度光学暂现源提供能量。
英文摘要
We present observations of the recent 2025.6 X-ray minimum and recovery of $η$~Carinae, obtained with NICER/XTI, Swift/XRT, XRISM/Xtend, and Chandra/HRC-I. We construct light curves in the soft (0.5--2 keV) and hard (2--10 keV) bands and derive hardness ratios. The X-ray emission reached its minimum about 10 days earlier than in the previous five cycles. As in previous events, the spectrum softened during the decline, while the X-ray luminosity varied on short timescales. These findings strengthen the conclusion that enhanced line-of-sight absorption, such as that expected during an eclipse, does not have a significant role in producing the spectroscopic event. Instead, they indicate that the X-ray decline is caused by stochastic variations and instabilities in the two stellar winds and their interaction, destruction of the colliding winds region, and accretion of primary wind onto the secondary. The main process behind the deep X-ray minimum near periastron is the accretion of mass lost by the primary star onto the secondary star. Accretion at periastron passages in $η$ Carinae implies that accretion occurred at much higher rates during the nineteenth-century Great and Lesser Eruptions, when the primary star lost mass at much higher rates. Such accretion likely launches jets. The broader implication is that accretion events in binary systems, possibly with jet launching, power other luminous blue variable giant eruptions and intermediate-luminosity optical transients.
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