发表机构
University of Southampton; University of Warwick; Institute of Space Sciences (ICE, CSIC); Institut d’Estudis Espacials de Catalunya (IEEC); Kapteyn Astronomical Institute, University of Groningen; Instituto Argentino de Radioastronoía (CCT La Plata, CONICET; CICPBA; UNLP); INAF – Osservatorio Astronomico di Capodimonte; Durham University; Coventry University; Instituto de Astronomía, Universidad Nacional Autónoma（南安普顿大学; 华威大学; 空间科学研究所（ICE，CSIC）; 加泰罗尼亚空间研究学院（IEEC）; 格罗宁根大学卡普坦天文研究所; 阿根廷射电天文研究所（CCT拉普拉塔，CONICET；CICPBA；UNLP）; 意大利国家天体物理研究所 - 卡波迪蒙特天文台; 杜伦大学; 考文垂大学; 天文学研究所，国立自治大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究利用OPTICAM多波段数据，在磁激变变星V709 Cas中发现频率依赖的红延迟（最大约4-6秒），并论证吸积盘亮斑中的复合过程可解释该延迟及其光谱特征。
AI 中文摘要
激变变星（CVs）是双星系统，其中白矮星（WD）主星通常通过吸积盘从晚型次星吸积物质。迄今为止，仅发现六颗激变变星（均为非磁系统）表现出延迟（一个波段相对于另一个波段的延迟变化）。在这六个案例中，这些延迟均为“红”延迟（即红光滞后于蓝光），时间延迟量级为秒。虽然目前尚无普遍接受的机制来解释激变变星中的红延迟，现有理论认为延迟源于吸积盘中的再处理过程，可能发生在热时标或复合时标上，或源于穿过吸积盘的由内向外传播的激波。利用光学定时相机（OPTICAM）的 g、r 和 i 波段数据，我们报告发现了 V709 Cas 的频率依赖红延迟：V709 Cas 是一颗属于中介偏振（IP）亚类的磁激变变星。这些红延迟在 7.4–13.0 分钟的时间尺度上最大可达约 4–6 秒，与先前在非磁激变变星中报告的延迟相似。在中介偏振星中探测到延迟具有重要意义，因为白矮星的磁场截断了吸积盘，将基于盘的延迟机制限制在大半径区域；因此，典型的吸积盘时间尺度无法解释观测到的延迟。然而，即使在吸积盘被截断的系统中，复合过程也可以在秒量级的时间尺度上发生。例如，我们表明，吸积盘亮斑（即从次星溢出的物质与吸积盘外缘相遇处）中的复合过程，可以合理地解释 V709 Cas 的光学光谱、光学自旋-轨道拍频脉动的显著性以及本工作中发现的红延迟。
英文摘要
Cataclysmic variables (CVs) are binary systems in which a white dwarf (WD) primary accretes material from a late-type secondary, typically via a disc. To date, only six CVs, all of which are non-magnetic, have been found to exhibit lags (delayed variability in one band with respect to another). In all six cases, these lags are ``red'' (i.e., red lags blue) with a time lag of order seconds. While there is no generally accepted mechanism for producing red lags in CVs, current theories suggest reprocessing in the disc, either on the thermal or recombination time-scales, or inside-out shocks propagating through the disc. Using $g$-, $r$-, and $i$-band data from the OPtical TIming CAMera (OPTICAM), we report the discovery of frequency-dependent red lags from V709 Cas: a magnetic CV of the intermediate polar (IP) subclass. These red lags reach a maximum of $\sim$4--6 s on time-scales of 7.4--13.0 min, similar to previously-reported lags in non-magnetic CVs. The detection of lags in an IP is significant as the WD's magnetic field truncates the accretion disc, limiting disc-based lag mechanisms to large radii; as a result, characteristic accretion disc time-scales cannot explain the observed lags. However, recombination can occur on second time-scales, even in systems with truncated discs. For example, we show that recombination in the disc's bright spot, where overflowing material from the secondary meets the outer-edge of the disc, plausibly explains V709 Cas's optical spectrum, the prominence of optical spin-orbit beat pulsations, and the red lags found in this work.
Comments17 pages, 10 figures, accepted for publication in MNRAS
