A previously unremarkable star near the Canis Major OB1/R1 association underwent an episode of multiple deep brightness minima. Light curves based on archival Gaia, ZTF, NEOWISE data and additional observations from LCO and UKIRT show that the star was not variable prior to 2019 Aug 18 (MJD 58700), and on that date started showing brightness dips of up to 3 magnitudes in the Gaia G and ZTF r bandpasses. After MJD 59500, ~800 days after the onset of these dipping events, the star returned to its previous brightness, and no significant dipping events have been recorded since. Compared to the stable phase, NEOWISE infrared photometry in the W1 and W2 bands indicates a generally redder color, and both decreases and increases in brightness at different times during the dipping episode. The spectrum of Gaia21bcv taken after the end of the dipping episode shows several neutral and ionized metal absorption lines, including Li, indicating a spectral type of ~ K5. Variable emission from [OI] was observed. The H alpha absorption in Gaia21bcv is too faint and irregular for this spectral type, indicating that the line is partly filled in by variable emission, a signature of weak episodic accretion. Gaia21bcv lies above the zero-age main sequence, but is much fainter than typical R CrB stars. We interpret the light curve of Gaia21bcv as being similar to the occultation events in Epsilon Aurigae, i.e., occultation by a disk around a companion object orbiting the primary star.
Solar flare-related eruptions followed by long-lasting occultation of the emission in the He II 304 A line and in microwaves
等离子体的温度接近色球层的一个是在太阳爆发喷射。这样的等离子体可以掩盖太阳活动区和安静区致密源的部分发射。吸收现象可以在微波范围内观察到所谓的“负爆发”，也可以在He II 304 A线中观察到。本文考虑了与相当强大的耀斑有关的三个爆发事件。从一次喷发的“负爆发”的多频记录中估计了喷发的吸收物质参数。在一些事件中，我们发现了一个爆发的暗条的“破坏”，它像云一样在一个巨大的区域上分散，作为304 A线发射的巨大凹陷。本文考虑了我们已知的三个事件中的一个。另一个事件是可能的。
Variability of Disk Emission in Pre-Main Sequence and related Stars. V. Occultation Events from the innermost disk region of the Herbig Ae Star HD 163296
HD 163296是一颗赫比格Ae型恒星，在2001年经历了V光度带亮度的戏剧性下降$\sim$ 0.8等，并在2002年经历了近红外亮度的增亮。由于这颗恒星拥有赫比格-哈罗天体，它们以流出的双极喷流的形式运动，因此有人认为亮度的下降是由于盘风中夹带的一团尘埃，阻挡了朝向恒星的视线。为了量化这一假设，我们研究了亮度下降，在可见光波长和亮度在近红外波长的HD 163296使用蒙特卡罗辐射转移代码，HOCHUNK 3D。我们创建了三个模型来理解这些事件。模型1描述了系统的静态。模型2描述了导致2001年亮度下降的结构变化。模型3描述了产生2002年观测到的近红外波长增亮所需的结构。模型2和模型3利用圆盘风和中心双极流的组合。通过在模型2和模型3中引入填充的双极腔，我们能够成功地模拟具有盘风的恒星的喷流状结构，并创造了系统亮度的下降和随后的增加。另一方面，当双极腔未填充时，模型1复制系统的静态。
The nature of ASASSN-24fw's occultation: modelling the event as dimming by optically thick rings around a sub-stellar companion
Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences（波兰科学院尼古拉·哥白尼天文学中心）；Inter-University Centre for Astronomy and Astrophysics（大学天文与天体物理联合中心）；Institute of Astronomy and Astrophysics, Academia Sinica（中央研究院天文及天文物理学研究所）；Instituto de Astrofísica de Canarias（加那利群岛天体物理学研究所）；Departamento de Astrofísica, Universidad de La Laguna（拉帕鲁纳大学天体物理学系）；European Space Agency (ESA)（欧洲空间局）；Division of Physics, Mathematics and Astronomy, California Institute of Technology（加州理工学院物理、数学与天文学部）
Complex Variability of the H$α$ Emission Line Profile of the T Tauri Binary System KH 15D: The Influence of Orbital Phase, Occultation by the Circumbinary Disk, and Accretion Phenomenae
Planetary Construction Zones in Occultation: Discovery of an Extrasolar Ring System Transiting a Young Sun-like Star and Future Prospects for Detecting Eclipses by Circumsecondary and Circumplanetary Disks
ASASSN-24fw: Candidate circumplanetary disk occultation of a main-sequence star
Johns Hopkins University（约翰斯·霍普金斯大学）；Institute for Advanced Study（高等研究院）；New Mexico State University（新墨西哥州立大学）；Moscow State University（莫斯科国立大学）；Charles University（查理大学）；Imperial College London（帝国理工学院）；Gemini Observatory（吉米尼天文台）；NSF’s NOIRLab（美国国家科学基金会NOIR实验室）；Silesian University of Technology（西里西亚理工大学）；University of Warsaw（华沙大学）；Jagiellonian University（雅盖隆大学）；National Observatory of Athens（雅典国家天文台）；National Centre for Nuclear Research（国家核研究中心）；Vilnius University（维尔纽斯大学）；University of North Carolina at Chapel Hill（北卡罗来纳大学教堂山分校）；University of Zielona Gora（绿山城大学）
