再论长蛇座EX爆发
Outbursts of EX Hydrae Revisited
摘要：
我们目前的光学光谱EX Hya在其1991年爆发。这次爆发的特征是次级恒星的正面受到白矮星的强烈照射，这是一种在HeII中强烈可见的溢出流，并且光变曲线下降，在双星和自旋阶段从0.1延伸到0.6。吸积幕和盘的内部区域的强辐射导致HeII的强发射和Hg和Hb发射的抑制。在早期的研究中，在静止状态下观察到圆盘溢流，其中溢流流材料以接近1000 km/s的高速调制。在突出时，溢流物质以更高的速度（~1500 km/s）调制。这些是沿着靠近白矮星的磁力线流动的速度。观测到物质在盘外缘附近聚集并与吸积幕共转的证据。在下降过程中，这种物质和吸积幕遮蔽了几乎所有接近双星相0.4的发射，导致下降。倾角极小值几乎与自旋脉冲极小值相对应。这为扩展的吸积幕以及物质与盘外缘的吸积幕共转提供了额外的证据。从这些观察，我们认为，一个机制类似的Spruit和Taam，其中爆发的结果，由于磁层外的物质的存储和释放，触发了EX Hya的爆发。其次是由于吸积引起的辐射感应辐射对次级恒星的辐射。
英文摘要：
We present optical spectroscopy of EX Hya during its 1991 outburst. This outburst is characterised by strong irradiation of the front face of the secondary star by the white dwarf, an overflowing stream which is seen strongly in HeII and by a dip in the light curves, which extends from 0.1-0.6 in the binary and spin phases. Strong irradiation of the accretion curtain and that of the inner regions of the disc led to strong emission of HeII and to the suppression of the Hg and Hb emission. Disc overflow was observed in quiescence in earlier studies, where the overflow stream material was modulated at high velocities close to 1000 km/s. In outburst, the overflowing material is modulated at even higher velocities (~1500 km/s). These are streaming velocities down the field lines close to the white dwarf. Evidence for material collecting near the outer edge of the disc and corotating with the accretion curtain was observed. In decline, this material and the accretion curtain obscured almost all the emission near binary phase 0.4, causing a dip. The dip minimum nearly corresponds with spin pulse minimum. This has provided additional evidence for an extended accretion curtain, and for the corotation of material with the accretion curtain at the outer edge of the disc. From these observations we suggest that a mechanism similar to that of Spruit & Taam, where outbursts result due to the storage and release of matter outside the magnetosphere, triggers the outbursts of EX Hya. This is followed by the irradiation of the secondary star due to accretion induced radiation.
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