2003,
Vol.3, No.4 (August 20, 2003)
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Invited Review
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Letter
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The Galaxy |
Cosmology
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Extragalactic
Astronomy
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Stars
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The Sun
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Measuring the Fundamental Parameters of Hot Hydrogen-Rich White Dwarfs M. A. Barstow Affiliation: Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK E-mail: mab@star.le.ac.uk
Abstract |
Discovery of Four Peculiar Variable Stars Xiao-Bin Zhang (1,2) and Rong-Xian Zhang (1) Affiliation: (1) National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (2) CAS-PKU Joint Beijing Astrophysics Center, Beijing 100871 E-mail: xzhang@bao.ac.cn (corresponding author) Abstract |
Non-LTE Analysis of the Sodium Abundance of Metal-Poor Stars in the Galactic Disk and Halo Yoichi Takeda (1), Gang Zhao (2), Masahide Takada-Hidai (3), Yu-Qin Chen (2), Yu-ji Saito (4) and Hua-Wei Zhang (5,6) Affiliation: (1) Komazawa University, Komazawa, Setagaya, Tokyo 154-8525, Japan (2) National Astronomical Observatories, CAS (NAOC), Beijing 100012, China (3) Liberal Arts Education Center, Tokai University, Hiratsuka, Kanagawa 259-1292, Japan (4) Department of Physics, Faculty of Science, Tokai University, Hiratsuka, Kanagawa 259-1292, Japan (5) Department of Astronomy, School of Physics, Peking University, Beijing 100871 (6) CAS-Peking University Joint Beijing Astrophysical Center, Beijing 100871 E-mail: takedayi@cc.nao.ac.jp (corresponding author)
Abstract |
A Check on the Cardassian Expansion Model with Type-Ia
Supernovae Data Li Cao Affiliation: National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 E-mail: caoli@bao.ac.cn Abstract We use the magnitude-redshift relation for the type Ia supernova data compiled by Riess et al. to analyze the Cardassian expansion scenario. This scenario assumes the universe to be flat, matter dominated, and accelerating, but contains no vacuum contribution. The best fitting model parameters are H0 = 65.3 ksm, n =0.35 and ![]() ![]() Key words: supernovae: general --- cosmology: theory --- distances and redshifts PDF file (593 KB) | gzipped PS file (138 KB) | Back to Contents |
On the Spectral Index-Flux Density Relation for Large Samples of Radio Sources Xi-Zhen Zhang (1), W. Reich (2), P. Reich (2) and R. Wielebinski (2) Affiliation: (1) National Astronomical Observatories, CAS (NAOC), Beijing 100012, China (2) Max-Planck-Institut f\"ur Radioastronomie, Auf dem H\"ugel 69, D-53121 Bonn, Germany E-mail: zxz@bao.ac.cn (coressponding author) Abstract We present new statistical results on the spectral index--flux density relation for large samples of radio sources using archival data of the most sensitive surveys, such as 6C, Miyun, WENSS, B3, NVSS, GB87. Instrumental selection effects and the completeness of the catalogs are discussed. Based on the spectral indices calculated for about 200000 sources from the WENSS (327 MHz) and NVSS (1.4 GHz) catalogs, we obtained (1) The median spectral index increases from ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() Key words: radio continuum: general --- methods: statistical --- cosmology PDF file (483 KB) | gzipped PS file (487 KB) | Back to Contents |
A Study of Neutron Star Structure in Strong Magnetic Fields that includes Anomalous Magnetic Moments Guang-Jun Mao (1,2), Akira Iwamoto (1) and Zhu-Xia Li (3) Affiliation: (1) Japan Atomic Energy Research Institute, Tokai, Naka, Ibaraki 319-1195, Japan (2) Institute of High Energy Physics, Chinese Academy of Science, Beijing 100039 (3) China Institute of Atomic Energy, Beijing 102413 E-mail: maogj@mail.ihep.ac.cn (corresponding author) Abstract We study the effect of strong magnetic fields on the structure of neutron star. We find that if the interior field is on the same order as the surface field currently observed, then the influences of the field on the star's mass and radius are negligible; if the field is as large as that estimated from the scalar virial theorem, then considerable effects will be induced. The maximum mass of the star will be increased substantially while the central density is greatly reduced. The radius of a magnetic star can be larger by about 10% ![]() Key words: stars: neutron stars --- stars: magnetic fields --- equation of state PDF file (256 KB) | gzipped PS file (332 KB)| Back to Contents |
Near Real-Time Calculation of Ionospheric Electric Fields and Currents Using GEDAS H. Shirai (1,2), Y. Kamide (1), E. A. Kihn (3), B. Hausman (4), M. Shinohara (1,5), H. Nakata (1,6), M. Isowa (1), T. K. Takada (1), Y. Watanabe (1), and S. Masuda (1) Affiliation: (1) Solar-Terrestrial Environment Laboratory, Nagoya University, Toyokawa, Aichi 442-8507, Japan (2) Now at Ichinoseki National College of Technology, Ichinoseki, Iwate 021-8511, Japan (3) NOAA National Geophysical Data Center, Boulder, Colorado 80303-3328, U.S.A. (4) Department of Physics and Astronomy, Rice University, Houston, Texas 77005-1892, U.S.A. (5) Now at Communications Research Laboratory, Koganei, Tokyo 184-8795, Japan (6) Now at Chiba University, Chiba, Chiba 263-8522, Japan E-mail: (corresponding author) Abstract This paper presents the recent progress in our project of estimating near real-time electric fields and currents in the ionosphere through our computer system called the Geospace Environment Data Analysis System (GEDAS). We show a new technique in which data from ground magnetometers are collected by the system and used as input for the KRM and AMIE programs to calculate the distribution of ionospheric electric fields and currents, as well as of other ionospheric parameters, such as electric potential patterns. One of the goals of this project is to specify ionospheric processes. Examples of the near real-time calculation and the data flow of our scheme are presented. Key words: data analysis --- solar-terrestrial relations PDF file (223 KB) | gzipped PS file (320 KB) | Back to Contents |
Solar Partial N-burst Zong-Jun Ning (1), Yu-Ying Liu (1), Qi-Jun Fu (1) and Fu-Ying Xu (2) Affiliation: (1) National Astronomical Observatories, CAS (NAOC), Beijing 100012, China (2) Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 E-mail: (corresponding author) Abstract We present a new sub-class of type III solar radio burst at the high frequencies around 6.0 GHz. In addition to a descending and an ascending branch on the dynamic spectrum, it has an inverted morphology different from the simple type U-burst. We call it ``partial N-burst'' because it is interpreted as the known N-burst minus its first branch. The partial N-burst presented here was detected among a reverse slope type III (RS-III) burst group prior to the type V solar radio continuum and was simultaneously recorded by two spectrometers at the National Astronomical Observatories, Chinese Academy of Sciences (NAOC, 5.20 ![]() ![]() Key words: Sun: radio radiation --- Sun: magnetic fields PDF file (1073 KB) | gzipped PS file (469 KB) | Back to Contents |
ChJAA, 2003, Vol.3,
No.4
Chinese Journal of Astronomy and Astrophysics:
Online Edition
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