Abstract—

Instrumentation for observing occultations of stars by Solar System bodies and its parameters are described. The complex is designed for observations at the AZT-2 telescope (D = 70 cm, F = 10.5 m) of the Main Astronomical Observatory of the National Academy of Sciences of Ukraine (МAO NASU); it is equipped with an optical reducer of the focal length and may also be mounted at the other telescopes. The observation complex uses the Apogee Alta U47 CCD camera as a light receiver, which operates in the drift scan mode. The results of the study of two phenomena that were observed with this complex are described. During the observations on September 21, 2018, a decrease of approximately 0.04^m in the brightness of the star HD 45314 was detected near the ephemeris moment of occultation by comet 21P/Giacobini−Zinner. This value exceeds the level of errors possible in the photometry of a stellar track. A possible explanation of this effect by the attenuation of light in a symmetrical dust coma of the comet was analyzed. It has been shown that this factor cannot yield the required magnitude of the light attenuation. The observed decrease in brightness is explained by the passage of the star through the jet structure with sharp boundaries, the optical thickness of which is 0.035 ± 0.012 and the opening angle is 54.6°. The single scattering albedo of dust particles in this jet is in the range of 0.04−0.06. The occultation of the star UCAC4-475-051755 by asteroid (259) Alethea was recorded on March 31, 2019, and it lasted for 16.7 s. This occultation duration corresponds to the asteroid chord 185 km long, while the expected one is 61 km, and it exceeds a value of 179 km accepted for this asteroid diameter. This difference is explained by the ellipsoidal shape of asteroid (259) Alethea, and the grounds for a value of 1 : 1.19 for its axial ratio are presented.

中文翻译：

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小行星（259）Alethea和彗星21P / Jacobini-Zinner的恒星掩星观测

摘要-

描述了用于观测太阳系天体掩星的仪器及其参数。该综合体是为在乌克兰国家科学院主要天文台（МAONASU）的AZT-2望远镜（D = 70 cm，F = 10.5 m）上进行观测而设计的；它配备了焦距光学衰减器，也可以安装在其他望远镜上。观测大楼使用Apogee Alta U47 CCD摄像机作为光接收器，该摄像机以漂移扫描模式运行。描述了用这种复合物观察到的两种现象的研究结果。在2018年9月21日的观测期间，减少了约0.04 ^m在彗星21P / Giacobini-Zinner掩星的星历时，检测到了恒星HD 45314的亮度。此值超过了恒星轨道光度法中可能出现的错误级别。通过对彗星对称尘埃彗形图中的光进行衰减，分析了这种影响的可能解释。已经表明，该因素不能产生所需的光衰减量。观察到的亮度下降是由于恒星穿过具有尖锐边界的射流结构而引起的，该结构的光学厚度为0.035±0.012，打开角度为54.6°。该射流中尘埃颗粒的单次散射反照率在0.04-0.06的范围内。小行星（259）Alethea对恒星UCAC4-475-051755的掩星记录于2019年3月31日进行，持续了16.7 s。该掩星持续时间对应于小行星弦长185 km，而预期的长为61 km，并且超过了该小行星直径可接受的179 km。小行星（259）Alethea的椭圆形状解释了这种差异，并给出了其轴向比率为1：1.19的依据。