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Micro-arcsecond Celestial Reference Frames: definition and realization — Impact of the recent IAU Resolutions
Capitaine, Nicole
The adoption of the International Celestial Reference System (ICRS), based on Very Long Baseline Interferometry (VLBI) observations of extragalactic radiosources by the International Astronomical Union (IAU) since 1998 January 1, opened a new era for astronomy. The ICRS and the corresponding frame, the International Celestial Reference Frame (ICRF…
Interpretation of the coronal magnetic field configuration of the Sun
Li, Xing; Li, Bo; Yu, Hui
The origin of the heliospheric magnetic flux on the Sun, and hence the origin of the solar wind, is a topic of hot debate. While the prevailing view is that the solar wind originates from outside the coronal streamer helmets, there also exists the suggestion that the open magnetic field spans a far wider region. Without the definitive measurement …
Studies of a possible new Herbig Ae/Be star in the open cluster NGC 7380
Mathew, Blesson; Banerjee, D. P. K.; Subramaniam, Annapurni +3 more
We present a study of the star 2MASS J22472238+5801214 with the aim of identifying its true nature which has hitherto been uncertain. This object, which is a member of the young cluster NGC 7380, has been variously proposed to be a Be star, a D-type symbiotic and a Herbig Ae/Be star in separate studies. Here we present optical spectroscopy, near-I…
Properties of the high-mass star forming region IRAS 22475+5939
Wang, Jun-Jie; Liu, Xiao-Lan
IRAS 22475+5939 has been well studied by previous astronomers, but we can still discover new characteristics about it, using the first observations of the lines from CO J=2-1, 13CO J=2-1 and 13CO J=3-2 by the KOSMA 3m telescope. The mapping of the intensity ratio of 13CO J=3-2 and 13CO J=2-1 shows that t…
Observations of EUV and soft X-ray recurring jets in an active region
Bi, Yi; Yang, Li-Heng; Jiang, Yun-Chun +3 more
We present simultaneous observations of three recurring jets in EUV and soft X-ray (SXR), which occurred in an active region on 2007 June 5. By comparing their morphological and kinematic characteristics in these two different wavelengths, we found that EUV and SXR jets had similar locations, directions, sizes and velocities. We also analyzed thei…
Fractal dimension and thermodynamic fluctuation properties of IDV light curves
Leung, Chun-Sing; Wei, Jian-Yan; Kovács, Zoltan +1 more
Fractals are a basic tool for phenomenologically describing natural objects having a high degree of temporal or spatial variability. From a physical point of view the fractal properties of natural systems can also be interpreted by using the standard formalism of thermodynamical fluctuations. We introduce and analyze the fractal dimension of the I…
Observing the reconnection region in a transequatorial loop system
Liu, Chang; Stenborg, Guillermo; Liu, Rui +4 more
A vertical current sheet is a crucial element in many flare/coronal mass ejection (CME) models. For the first time, Liu et al. reported a vertical current sheet directly imaged during the flare rising phase with the EUV Imaging Telescope (EIT) onboard the Solar and Heliospheric Observatory (SOHO). As a follow-up study, here we present the comprehe…
Systematic differences in position and proper-motion between the PPMX and UCAC3 catalogs
Zhu, Zi; Liu, Jia-Cheng; Hu, Bo
Considered to be extensions of the Hipparcos reference system, PPMX and UCAC3 are two of the most important astrometric catalogs released in current years. Extensive analyses of these two large catalogs have been made in order to determine the local and overall systematic biases. The regional and magnitude dependent differences in stellar position…
XMM-Newton observation of the eclipsing binary Algol
Chen, Li; Aschenbach, Bernd; Lu, Fang-Jun +1 more
We present an XMM-Newton observation of the eclipsing binary Algol which contains an X-ray dark B8V primary and an X-ray bright K2IV secondary. The observation covered the optical secondary eclipse and captured an X-ray flare that was eclipsed by the B star. The XMM-Newton European Photon Imaging Camera and Reflection Grating Spectrometer spectra …
Detailed study of B037 based on HST images
Ma, Jun
B037 is of interest because it is both the most luminous and the most highly reddened cluster known in M31. Deep observations and high spatial resolution images with the Advanced Camera for Surveys on the Hubble Space Telescope (HST) first showed that this cluster is crossed by a dust lane. Photometric data in the F606W and F814W filters obtained …