AI 中文总结
研究对γ Cas类似物短期X射线行为进行系统评估，通过生成功率谱等方法，对26个类似物及候选源的131次探测分析，识别出五个有重复周期变化的源等，发现其短期X射线变化特性与其他吸积WD系统一致。
AI 中文摘要
背景。总体而言，γ Cas类似物是一类显示明亮且硬X射线发射的OBe星。这种发射最近被确定是吸积到伴白矮星（WD）上的结果，该白矮星可能是磁WD。目的。我们对γ Cas类似物在短期（千秒，ks）尺度上的特性进行系统综述，以进一步研究X射线源的性质。特别是，周期性的存在可能与磁WD的旋转有关。方法。我们生成了功率谱和广义傅里叶算法。我们对26个γ Cas类似物和两个候选源的131次X射线探测应用了历元折叠方法以及Z2n方法。结果。我们识别出五个源（γ Cas、ζ Tau、HD45314、V771 Sgr和π Aqr）在观测中具有重复的周期性变化（P ~ 1.2 - 5.4 ks）。周期值和脉冲分数与中间极化星的报告值一致。然而，虽然在一个物体的所有曝光中发现了相似的周期，但确切的周期值或折叠光曲线形状可能会变化。我们还识别出另外九个显示周期性但无法确认的源，因为只有一次观测可用于分析。在其他情况下，周期性最多是瞬态的和/或边缘显著的。18个源的非周期性变化可以用幂律拟合，幂律指数总是~ 1，这与其他吸积WD中观察到的情况一样。结论。观测到的γ Cas类似物短期X射线变化的整体特性与其他吸积WD系统中观察到的一致。
英文摘要
Context. Overall, $γ$ Cas analogues represent a class of OBe stars displaying bright and hard X-ray emission. This emission was recently determined to be the result of accretion onto a companion white dwarf (WD), which might possibly be a magnetic WD. Aims. We present a systematic review of the properties of $γ$ Cas analogues on short-term (kilosecond, ks) scales to further investigate the nature of the X-ray source. In particular, the presence of periodicities could be associated with the rotation of a magnetic WD. Methods. We generated the power spectra and a generalised Fourier algorithm. We applied an epoch folding method, along with Z2n approaches, to 131 X-ray detections of 26 $γ$ Cas analogues and two candidate sources. Results. We identified five sources ($γ$ Cas, $ζ$ Tau, HD45314, V771 Sgr, and $π$ Aqr), with recurrent periodic variability (P $\sim$ 1.2-5.4 ks) across observations. Period values and pulsed fractions are consistent with those reported for intermediate polars. However, while similar periods are found in all exposures of an object, the exact period value or folded light curve shape can vary. We also identify another nine sources displaying periodicities that cannot be confirmed, as there was only one observation available for their analysis. In other cases, periodicities appear (at best) transient and/or marginally significant. Aperiodic variability could be fitted by a power law in 18 of the sources, while the power-law index always is $\sim$ 1, as observed in other accreting WDs. Conclusions. The global properties of the observed short-term X-ray variability of the $γ$ Cas analogues are consistent with those observed from other accreting WD systems.
CommentsAccepted for publication in A&A
Journal refA&A, 713, A163 (2026)
DOI：10.1051/0004-6361/202660455
