这颗独特的天蝎座AR双星由一颗异步旋转的磁化白矮星（WD）组成，它与它的红矮星伴星相互作用，每1.97分钟产生一次大振幅、高度相干的脉动。在两年的时间里，我们以5秒的典型节奏获得了39小时的时间分辨的AR Sco的光学测光，以研究这种脉动。我们发现，它经历了显着的变化，整个双星轨道周期，其振幅，相位和波形都作为轨道相位的函数而变化。我们表明，这些变化可以解释的建设性和相消干涉之间的两个周期性的，双峰信号：自旋轨道拍脉冲，和一个较弱的WD自旋脉冲。光变曲线的建模表明，在光学中，主自旋脉冲的振幅是主拍振幅的50%，而拍频脉冲和自旋脉冲的次最大值具有相似的振幅。最后，我们使用我们的节拍脉冲的定时，以确认存在争议的旋转下降的WD。我们测量到拍频导数为-5.14（32）x 10^-17 Hz/s，并表明这是由于WD的自旋下降。这一数值大约是Marsh et al.（2016）估计值的两倍，但与Potter & Buckley（2018）建立的约束条件一致。我们对自旋下降速率的精确测量证实，磁化白矮星的衰变旋转能量足以为双星发出的多余电磁辐射提供动力。
英文摘要：
The unique binary AR Scorpii consists of an asynchronously rotating, magnetized white dwarf (WD) that interacts with its red-dwarf companion to produce a large-amplitude, highly coherent pulsation every 1.97 minutes. Over the course of two years, we obtained thirty-nine hours of time-resolved, optical photometry of AR Sco at a typical cadence of 5 seconds to study this pulsation. We find that it undergoes significant changes across the binary orbital period and that its amplitude, phase, and waveform all vary as a function of orbital phase. We show that these variations can be explained by constructive and destructive interference between two periodic, double-peaked signals: the spin-orbit beat pulse, and a weaker WD spin pulse. Modelling of the light curve indicates that in the optical, the amplitude of the primary spin pulse is 50% of the primary beat amplitude, while the secondary maxima of the beat and spin pulses have similar amplitudes. Finally, we use our timings of the beat pulses to confirm the presence of the disputed spin-down of the WD. We measure a beat-frequency derivative of -5.14(32) x 10^-17 Hz/s and show that this is attributable to the spin-down of the WD. This value is approximately twice as large as the estimate from Marsh et al. (2016) but is nevertheless consistent with the constraints established in Potter & Buckley (2018). Our precise measurement of the spin-down rate confirms that the decaying rotational energy of the magnetized white dwarf is sufficient to power the excess electromagnetic radiation emitted by the binary.
Confirmation of simultaneous p and g mode excitation in HD 8801 and Gamma Peg from time-resolved multicolour photometry of six candidate "hybrid" pulsators
Parallaxes, Proper Motions, and Near-Infrared Photometry for 173 L and T Dwarfs From The US Naval Observatory Infrared Astrometry Program
United States Naval Observatory（美国海军天文台）；Flagstaff Dark Skies Coalition（弗拉格斯塔夫黑暗天空联盟）；L-3 Communications/Brashear（L-3通信/布莱尔）；Gemini Observatory/NSF’s NOIRLab（吉米尼天文台/美国国家科学基金会NOIR实验室）；California Institute of Technology (IPAC)（加州理工学院（IPAC））；Center for Astrophysics and Space Science, University of California San Diego（加州大学圣地亚哥分校天体物理与空间科学中心）
Red supergiant stars in binary systems II. Confirmation of B-type companions of red supergiants in the Small Magellanic Cloud using Hubble ultra-violet spectroscopy
J0404+1112: A 3-Hour Eclipsing White Dwarf-Brown Dwarf Probing Multiple Atmospheric Regimes
Massachusetts Institute of Technology（麻省理工学院）；Instituto de Astrofísica de Canarias (IAC)（加那利天体物理学研究所）；Universidad de La Laguna (ULL)（拉古纳大学）；NASA Johnson Space Center（美国国家航空航天局约翰逊航天中心）；University of Leicester（莱斯特大学）；University of Virginia（弗吉尼亚大学）；University of Birmingham（伯明翰大学）
