Fig: (left) The mHz QPO dynamic power spectra of 4U 1636-53 from the data collected by XMM-Newton in 2008. (right) The Hilbert spectra from the same data analyzed by HHT whereas the contours are the dynamic power spectra. It is evidently that the Hilbert spectra can provide better precision in time-frequency analysis.
Fig: The pulse phase evolution of accreting millisecond pulsar IGR J17591-234 under
the assumption of constant pulsation frequency. The best fitted quadratic curve (the
red dashed line) indicates that the spin frequency derivative of the neutron star is (-6±1)x10-14 Hz/s. According to the accretion torque theory, the surface magnetic field of this
neutron star is estimated as about 4x108 Gauss.
Fig: The Asteroid Rotation Period Survey Using the CNEOST
Prof. Ngeow: Kundu et al (2019) identified 5 extra-tidal RR Lyrae that could be associated with globular cluster NGC5024, shown as red squares in the above picture. However, 4 of them actually belong to a nearby globular cluster NGC5053, where the known RR Lyrae in this globular cluster is marked with green crosses. Using Gaia and ZTF data, we further searched for possible extra-tidal RR Lyrae that could be associated with both of the globular clusters, and we found none. This work is published in Ngeow et al (2020) AJ 160:31.
Dr. Chien-De Lee: HO Pup is an new discovered dwarf nova by ZTF and NCU. Dwarf nova is a mass transfer binary including a mass donor star and a white dwarf surrounded by the accretion disk. In 2019, we observed the variation of Hα line from 3/15-3/22 with CFHT/EsPADOnS spectroscopy. The brightening part of the outburst was fully observed at these eight nights. When the outer disk accretes enough mass, here coms the photometric brightening. Before the luminosity maximum, the absorption part of Hα line was obviously shown in the spectra of HO Pup. Mass transfer rate of accretion play a major role behind this photometric and spectroscopic variability. (Including Prof. C.-C. Ngeow and Ph.D student J.-Y. Ou)
Figure. The flare frequency distribution of different energy release levels
of M-type stars.
陳文屏教授：利用 Gaia 太空望遠鏡的精確恆星距離與運動數據，研究距離我們約750光年，年齡約1億年的年輕星團 Blanco 1，一共指認出644顆成員星，包括488顆位於星團核心，表示此星團目前仍處於動力穩定狀態，但已經顯示質量分層效應，也就是大質量成員星集中在中央區域。我們首度發現 Blanco 1 有潮汐尾，分別在星團核心（33光年）兩端，延伸長達180光年，亦顯示星團正開始瓦解。右圖展示星團成員的質量函數，在0.2～0.3太陽質量達到最高。垂直線標示數據的完整極限，目前尚未涵蓋棕矮星 （< 0.1太陽質量）。這項研究成果發表在 Zhang et al. Astrophysical Journal (2020), 889, 99
Fig: Radial Acceleration Relation in CLASH Galaxy Clusters
Fig. Asteroid Discovery and Light Curve Extraction Using the Hough Transform: A Rotation Period Study for Subkilometer Main-belt Asteroids