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Verification of Short-Term Predictions of Solar Soft X-ray Bursts for the Maximum Phase (2000-2001) of Solar Cycle 23

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chinese Journal of Astronomy and Astrophysics 2003年第6期3卷 563-568页

作者： Cui-Lian Zhu and Jia-Long Wangnational astronomical observatories, chinese academy of sciences, beijing 100012 national astronomical observatories Chinese Academy of Sciences Beijing 100012

We present a verification of the short-term predictions of solar X-ray bursts for the maximum phase (2000–2001) of Solar Cycle 23, issued by two prediction centers. The results are that the rate of correct predictions is about equal for RWC-china and WWA; the rate of too high predictions is greater for RWC-china than for WWA, while the rate of too low predictions is smaller for RWC-china than for WWA.

关键词： sun: X-ray bursts sun: short-term prediction

Searching for Variable Stars in and around Open Clusters

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chinese Journal of Astronomy and Astrophysics 2002年第6期2卷 481-486页

作者： Yu Xin, Xiao-Bin Zhang and Li-Cai Dengnational astronomical observatories, chinese academy of sciences, beijing 100012 national astronomical observatories Chinese Academy of Sciences Beijing 100012 China

We present a snapshot-of our recent results of a variable star survey in 1 degree fields around three open clusters: NGC 188, NGC 7789 and M67. A total number of 39 variable stars are newly discovered, including 22 W ... 详细信息

关键词： open clusters : individual : NGC 188, NGC 7789 and M67 stars : variables

A Note on the Mixing Length Theory and Massive Star Evolution

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chinese Journal of Astronomy and Astrophysics 2001年第1期1卷 50-56页

作者： Li-Cai Deng and Da-Run Xiong ( beijing astronomical Observatory, chinese academy of sciences, beijing 100012 Purple Mountain Observatory, chinese academy of sciences, Nanjing210008 national astronomical observatories, chinese academy of sciences, Beij beijing astronomical Observatory Chinese Academy of Sciences Beijing 100012 national astronomical observatories Chinese Academy of Sciences Beijing 100012 CAS-Peking University Joint beijing Astrophysical Center Beijing 100871 Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008

In this paper, we investigate the problem of supersonic convection caused by the application of the usual Mixing Length Theory (MLT), and give a modification to the original expression of the MLT. In the case of the usual MLT, a zone of supersonic convection exists when the stellar model goes into yellow-red supergiant phase. When the modification is applied, the models of late type supergiants possess shallower convective envelopes for a given temperature compared with the normal formalism of the MLT. Therefore the stellar models made with our new formalism move to lower effective temperature by 100-400 K depending on the luminosity of the star. Such a modification does not affect the convective envelope structure of lower luminosity late type stars, as both expressions of the MLT give the same result. In these stars.

关键词： convection - stars: supergiants - stars: massive stars - stars: evolution

Wavelet Analysis of the Schwabe Cycle Properties in Solar Activity

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chinese Journal of Astronomy and Astrophysics 2004年第6期4卷 578-582页

作者： Gui-Ming Lenational astronomical observatories, chinese academy of sciences, beijing 100012 Center for Space Science and Applied Research Center, chinese academy of sciences, beijing 100080 national astronomical observatories Chinese Academy of Sciences Beijing 100012 Center for Space Science and Applied Research Center Chinese Academy of Sciences Beijing 100080

Properties of the Schwabe cycles in solar activity are investigated by using wavelet transform. We study the main range of the Schwabe cycles of the solar activity recorded by relative sunspot numbers, and find that the main range of the Schwabe cycles is the periodic span from 8-year to 14-year. We make the comparison of 11-year’s phase between relative sunspot numbers and sunspot group numbers. The results show that there is some difference between two phases for the interval from 1710 to 1810, while the two phases are almost the same for the interval from 1810 to 1990.

关键词： sun sunspot sun activity method data analysis

The Hβ Chromospheric Magnetic Field in a Quiescent Filament

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chinese Journal of Astronomy and Astrophysics 2003年第1期3卷 87-94,i002-i004页

作者： Xing-Ming Bao and Hong-Qi Zhangnational astronomical observatories, chinese academy of sciences, beijing 100012 baoxm@*** national astronomical observatories CAS NAOC Beijing 100012 China

We observed the line-of-sight magnetic field in the chromosphereand photosphere of a large quiescent filament on the solar disk on September 6, 2001 using the Solar Magnetic Field Telescope in Huairou Solar Observing Station. The chromospheric and photospheric magnetograms together with Hβ filtergrams of the filament were examined. The filament was located on the neutral line of the large scale longitudinal magnetic field in the photosphere and the chromosphere. The lateral feet of the filament were found to be related to magnetic structures with opposite polarities. Two small lateral feet are linked to weak parasitic polarity. There is a negative magnetic structure in the photosphere under a break of the filament. At the location corresponding to the filament in the chromospheric magnetograms, the magnetic strength is found to be about 40-70 Gauss (measuring error about 39 Gauss). The magnetic signal indicates the amplitude and orientation of the internal magnetic field in the filament. We discuss several possible causes which may produce such a measured signal. A twisted magnetic configuration inside the filament is suggested .

关键词： Sun: chromosphere - Sun: filaments - Sun: magnetic fields

Polarization Position Angle Swings caused by Relativistic Effects

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chinese Journal of Astronomy and Astrophysics 2003年第1期3卷 75-86页

作者： Shan-Jie Qian and Xi-Zhen Zhangnational astronomical observatories, chinese academy of sciences, beijing 100012 rqsj@*** national astronomical observatories CAS NAOC Beijing 100012 China

Polarization position angle swings of 180° observed in extragalactic radio sources are a regular behavior of variability in polarization. They should be due to some kind of physically regular process. We consider relativistic shocks which propagate through and `illuminate' regular configurations of magnetic field, producing polarization angle swing events. Two magnetic field configurations (force-free field and homogeneous helical field) are considered to demonstrate the results. It is shown that the properties of polarization angle swings and the relationship between the swings and variations in total and polarized flux density are critically dependent on the configuration of magnetic field and the dynamical behavior of the shock. In particular, we find that in some cases polarization angle swings can occur when the total and polarized flux densities only vary by a very small amount. These results may be useful for understanding the polarization variability with both long and short timescales observed in extragalactic radio sources.

关键词： radio continuum: galaxies polarization galaxies: magnetic fields

astronomical function and date of the Taosi observatory

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Science china(Physics,Mechanics & Astronomy) 2009年第1期52卷 151-158页

作者： WU JiaBi1, CHEN MeiDong2 & LIU CiYuan3 1 national astronomical observatories, chinese academy of sciences, beijing 100012, china 2 Institute for the History of Natural Science, chinese academy of sciences, beijing 100010, china 3 national Time Service Center, chinese academy of sciences, Xi’an 710600, china national astronomical observatories Chinese Academy of Sciences Beijing China Institute for the History of Natural Science Chinese Academy of Sciences Beijing China national Time Service Center Chinese Academy of Sciences Xi’an China

The Taosi site in Xiangfen County,Shanxi Province,may be the capital of the King Yao. Archeologists recently discovered a large semi-circular stamped-earth platform, II FJT1,which has a clear and definite pounded-earth central core together with a curved wall perforated by twelve gaps. The platform is said to be an ancient observatory used to determine the seasons by watching the sunrise. Each feature of II FJT1 was precisely measured and the data are reproduced in this paper. An astronomical analysis of slots E2 and E12 was carried out using the azimuths of the slots' centerlines and the vertical angle of the mountain ridge opposite, above which the sun rises. The results show that at present the sun is close to the two slots but does not exactly enter them at summer and winter solstice sunrise. Using 14C analysis archeologists dated the site to about 2100 BC. Because of the secular change in the obliquity of the ecliptic,at that date on the summer solstice the half-risen sun would have appeared inside slot E12 just to the right of the centerline,and on the winter solstice the sun would have been exactly on the centerline of slot E2. This result provides compelling proof that II FJT1 is an ancient observatory.

关键词： astro-archeology astro-chronology Taosi culture ancient observatory time service

Discrepancy between infrared and optical emission in some Be stars

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chinese Science Bulletin 2002年第18期47卷 1511-1513页

作者： LIU Qingzhong & WEI JianyanPurple Mountain Observatory, chinese academy of sciences, Nanjing210008, china national astronomical observatories, chinese academy of sciences, beijing 100012, china Purple Mountain Observatory Chinese Academy of Sciences Nanjing China national astronomical observatories Chinese Academy of Sciences Beijing China

An expanding ring model is put forward to investigate the original regions of Ha line emission and infrared excess emission in Be stars, by taking optical depth into account. We find that the two regions depend strongly on the physical properties of the envelope of Be stars such as the initial density and density structure. This model can be used to qualitatively interpret the disagreement between the near infrared excess and the equivalent width (EW) of Ha emission line, as observed in some Be stars.

关键词： Be star emission line near infrared excess.

A Possible Origin of 6.7 GHz Linear Methanol Maser Sources

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chinese Journal of Astronomy and Astrophysics 2001年第5期1卷 389-394页

作者： Ye Xu (Shanghai astronomical Observatory, chinese academy of sciences, Shanghai 200030) (Urumqi astronomical Observatory, chinese academy of sciences, Urumqi 830011) (national astronomical observatories, chinese academy of sciences, beijing 100012) E-mail Shanghai astronomical Observatory Chinese Academy of Sciences Shanghai 200030 Urumqi astronomical Observatory Chinese Academy of Sciences Urumqi 830011 national astronomical observatories Chinese Academy of Sciences Beijing 100012

We present a model which explains the observed multi-linear spatial structures with different velocity gradients of the 50-61A+ methanol line at 6.7 GHz. We consider this and other hypotheses and conclude that the met... 详细信息

关键词： masers - stars: circumstellar matter - stars: formation