A photometric monitoring campaign has been conducted in order to investigate the character and origin of flaring events occasionally seen in the long-term low-state light curve of the polar prototype AM Her. Four telescopes employed during 2004 May–July revealed that the events have typical duty cycles of 2%–35%, amplitudes of 0.2–0.6 mag, and typical durations of 15–90 minutes. A striking concentration of the 2004 events appears near inferior and superior conjunction of the secondary star. Interestingly, in the long-term RoboScope-monitored light curve (1990–2003), similar events are uniformly distributed in phase. AM Her's accretion geometry and the nature of its low states allow for two likely origins for the observed events, namely, residual accretion during low states and activity (flares) on the secondary star. Considering that AM Her is likely a one-pole accretor in the low states, the former requires irregular mass transfer from the secondary, resulting in random accretion bursts, with cyclotron beaming concentrating the flares into two phase intervals. On the other hand, considering the stability of the magnetic poles, this cannot address the random distribution of the events during the long-term light curve. Drifting active regions on the secondary star could explain the random distribution of the events; however, coincidence must be invoked to explain their occurrence at the observed phases of orbital conjunction. A combination of the two ideas is also discussed, in which stellar activity on the secondary star induces random accretion bursts, with cyclotron beaming then concentrating the flares into two phase intervals.
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机译：为了调查偶尔发生在极地原型AM Her的长期低态光曲线中的耀斑事件的特征和起源，进行了光度监测运动。 2004年5月至7月期间使用了四架望远镜，这些事件的典型占空比为2％至35％，振幅为0.2至0.6 mag，典型持续时间为15至90分钟。 2004年事件的引人注目的集中出现在次要恒星的劣等结合附近。有趣的是，在RoboScope监测的长期光曲线（1990-2003年）中，相似的事件在相中均匀分布。 AM Her的吸积几何形状及其低态的性质为观察到的事件提供了两个可能的起源，即，低态时的残留增生和副星的活动（耀斑）。考虑到AM Her在低状态下可能是单极加速器，因此前者需要从次级状态进行不规则的质量转移，从而导致随机的增生爆发，而回旋加速器波束将火炬集中到两个相位间隔中。另一方面，考虑到磁极的稳定性，这不能解决长期光曲线期间事件的随机分布。次级恒星上活动区域的漂移可以解释这些事件的随机分布。但是，必须用巧合来解释它们在所观察到的轨道合相阶段的发生。还讨论了这两种想法的组合，其中次级恒星上的恒星活动会引起随机的增生爆发，然后用回旋加速器束将耀斑集中成两个相位间隔。
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