At any one time, approximately one-quarter of the most rapidly rotating normal A-type dwarfs (V sin i ≥ 200 km s~(-1)) show shell lines of Ti Ⅱ in the near-ultraviolet. Our observations during 22 years show that the lines appear and disappear on timescales of decades but do not display significant changes within 1 year. This implies that they are not remnants of the star formation but rather are probably caused by sporadic mass-loss events. A working hypothesis is that all A-type stars that are rotating near their limits have these shells, but for only one-quarter of the time. Because these lines do not appear in stars with smaller sin i, the shells must be disks. These are hot inner disks that may or may not be related to the cool outer disks seen by Smith and Terrile around β Pic or through infrared excesses around Vega and other A-type dwarfs. The similar, limited line widths indicate that the disks are ～7 R_* above the stellar surfaces.
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机译：在任何时候，旋转最快的正常A型矮星（V sin i≥200 km s〜（-1））中大约有四分之一在近紫外线中显示出TiⅡ的壳线。我们对22年的观察表明，这些线以几十年的时间尺度出现和消失，但在1年内没有显示出明显的变化。这意味着它们不是恒星形成的残余，而是可能由零星的质量损失事件引起。一个可行的假设是，所有在其极限附近旋转的A型恒星都具有这些壳，但是只有四分之一的时间。因为这些线不会出现在具有较小正弦i的恒星中，所以壳必须是圆盘。这些是热的内盘，可能与史密斯和Terrile在βPic附近看到的冷外盘有关，也可能与Vega和其他A型矮星周围的红外过剩有关。相似的有限线宽表示圆盘在恒星表面上方约〜7 R_ *。
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