中极区XY Ari的旋进吸积盘？
A precessing accretion disc in the intermediate polar XY Ari?
摘要：
白羊座XY是唯一一个显示其白矮星的深X射线日食的中间极地。先前发表的Ginga和Chandra的观测也揭示了一个广泛的X射线轨道调制，大致与日食反相，并推测是由于吸积盘边缘附近的扩展结构的吸收。在1996年的一次爆发中，RXTE观测到的X射线脉冲轮廓是单峰的，但通常观测到的X射线脉冲轮廓是双峰的。我们用RXTE观测了XY Ari，并分析了ASCA和XMM-Newton对该系统的先前未发表的档案观测。这些观察包括六次单独的访问，时间跨度约为十年。各种X射线观测表明，宽轨道调制在相位和意义上各不相同，然后在过去几年中最终完全消失。此外，X射线脉冲轮廓显示出深度和形状的变化，并且在最近的RXTE观测中没有显示出硬度比变化的证据。观察到的变化表明，脉冲轮廓和轨道调制都是由于在RXTE观测时的几何效应，而不是先前看到的光电吸收的相位依赖性变化。我们认为，这是一个旋进，倾斜吸积盘在这个系统中的证据。圆盘的进动使结构从我们的视线中移出，既在它的外边缘（改变轨道调制），也在它的内边缘，吸积幕被锚定（改变脉冲轮廓）。
英文摘要：
XY Ari is the only intermediate polar to show deep X-ray eclipses of its white dwarf. Previously published observations with Ginga and Chandra have also revealed a broad X-ray orbital modulation, roughly antiphased with the eclipse, and presumed to be due to absorption in an extended structure near the edge of an accretion disc. The X-ray pulse profile is generally seen to be double-peaked, although a single-peaked pulse was seen by RXTE during an outburst in 1996.We intended to investigate the cause of the broad orbital modulation in XY Ari to better understand the accretion flow in this system and other intermediate polars. We observed XY Ari with RXTE and analysed previously unpublished archival observations of the system made with ASCA and XMM-Newton. These observations comprise six separate visits and span about ten years. The various X-ray observations show that the broad orbital modulation varies in phase and significance, then ultimately disappears entirely in the last few years. In addition, the X-ray pulse profile shows variations in depth and shape, and in the recent RXTE observations displays no evidence for changes in hardness ratio. The observed changes indicates that both the pulse profile and the orbital modulation are solely due to geometrical effects at the time of the RXTE observations, rather than phase-dependent variations in photoelectric absorption as seen previously. We suggest that this is evidence for a precessing, tilted accretion disc in this system. The precession of the disc moves structures out of our line of sight both at its outer edge (changing the orbital modulation) and at its inner edge where the accretion curtains are anchored (changing the pulse profile).
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
