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Vilnius Photometry and Reddening of the Young Open Cluster NGC 6913

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Chinese Journal of Astronomy and Astrophysics 2001年第4期1卷 333-343页

作者： Jun-Jie Wang and Jing-Yao Hu (National Astronomical Observatories, Chinese academy of sciences, beijing 100012 beijing Astronomical Observatory, Chinese academy of sciences, beijing 100012 Chinese academy of sciences-peking university joint beijing As National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 beijing Astronomical Observatory Chinese Academy of Sciences Beijing 100012 Chinese academy of sciences-peking {3. joint beijing Astrophysical Center Beijing 100871

stars in the NGC 6913.field with both UBV and Vilnius photometry are selected to be the sample. The membership probability of the stars is greater than 50%. The correlation among Vilnius photometry, UBV photometry and reddening in the cluster is reviewed. It is found that the photometry in the Vilnius X, Y and Z bands can be used to make rough spectral classification. The values of E(B - V) are well correlated with the Vilnius colors of X - Y, Y - Z, Z - V and V - S in NGC 6913. The ratio of (V - S)/(Y - Z) of the MPCM (Most Possible Cluster Members) is a constant (1.3. -±0.06), and has no effect on the values of E(B - V), (B - V)0 and V0. Comparing with the observational data of all the stars of NGC 6913.region, we propose that the value of (V - S)/(Y - Z) can probably be used to select the preliminary candidates of one open cluster. In addition, 12 variable stars are discovered in the NGC 6913.region, in which star #155 has a variation with an amplitude of 4.25 mag.

关键词： Galaxy: open clusters and associations - ISM: dust extinction

Infall and Outflow Activities in the Be star FY CMa

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Chinese Journal of Astronomy and Astrophysics 2001年第6期1卷 514-524页

作者： Hui-Lai Cao National Astronomical Observatories, Chinese academy of sciences, beijing 100012 CAS-PKU {3. beijing Astrophysics Center, peking university, beijing 100871 National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 CAS-PKU joint beijing Astrophysics Center Peking University Beijing 100871

Unusual activity of outflow mass motion connected with infall events was recorded for the B0.5 IVe star FY CMa in February 1987 from both archival IUE spectrograms of circumstellar N v resonance lines and optical spectra of Ha and HeI γ5876 A emission lines which showed inverse P Cygni-type profiles. We estimate the mass loss rate using ultraviolet Si IVresonance lines with expanding atmosphere modeling calculations, and describe how the radial pressure performs the dominant role in accelerating the stellar wind. We attempt to give a qualitative explanation for the activity observed for FY CMa in terms of circumstellar matter raining down to the star.

关键词： line: proffles - stars: activity - stars: emission-line Be -circumstellar matter - stars: mass-loss - ultraviolet: stars

ON THE CENTRAL RELAXING SCHEME Ⅱ: SYSTEMS OF HYPERBOLIC CONSERVATION LAWS

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Journal of Computational Mathematics 2001年第6期19卷 571-582页

作者： Hua-zhong Tang (School of Mathematical sciences, peking university, {3. 100871, China) (LSEC,ICMSEC academy of Mathematics and Systems sciences, Chinese academy of sciences, {3. 100080, China) School of Mathematical sciences Peking University Beijing 100871 China

This paper continues to study the central relaxing schemes for system of hyperbolic conservation laws, based on the local relaxation approximation. Two classes of relaxing systems with stiff source term are introduced to approximate system of conservation laws in curvilinear coordinates. Based on them, the semi-implicit relaxing schemes are con- structed as in [6, 12] without using any linear or nonlinear Riemann solvers. Numerical experiments for one-dimensional and two-dimensional problems are presented to demon- strate the performance and resolution of the current schemes.

关键词： Hyperbolic conservation laws The relaxing system The central relaxing schemes The Euler equations.

CONVERGENCE OF VORTEX METHODS FOR 3.D EULER EQUATIONS

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Journal of Computational Mathematics 2000年第3期18卷 239-250页

作者： Jia-fu Lin (Institute of System Science, academy of Mathematics and System sciences, Chinese academy of sciences, beijing, 100080, China School of Mathematical sciences, peking university, beijing 100871, China) 中科院系统科学所北京 100080

Presents a study on the convergence of vortex methods for the three-dimensional Euler equations in bounded domains. Related studies on the convergence of vortex methods; Formulation of vortex methods; Convergence for ... 详细信息

关键词： Euler equations vortex methods convergence initial-boundary value problem

The regular representation and regular covariant representation of crossed products of Woronowicz C^(*)-algebras

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Science China Mathematics 2005年第9期48卷 1245-1259页

作者： ZHANG Xiaoxia~(1,2) & GUO Maozheng~(1,3. 1. School of Mathematical sciences,peking university,{3. 100871,China 2. Department of Mathematics,Yantai university,Yantai 264005,China 3. LMAM,peking university,{3. 100871,China School of Mathematical sciences Peking University Beijing China Department of Mathematics Yantai University Yantai China LMAM Peking University Beijing China

In this paper,it is shown that the regular representation and regular covariant representation of the crossed products A×α G correspond to the twisted multiplicative unitary operators,where A is a Woronowicz C~*-algebra acted upon by a discrete group ***,it is also shown that the regular covariant C~*-algebra is the Woronowicz C~*-algebra which corresponds to a multiplicative ***,an explicit description of the multiplicative unitary operator for C(SU_q(2) )×α (?) is given in terms of those of the Woronowicz C~*-algebra C(SU_q(2) ) and the discrete group G.

关键词： multiplicative unitary operator, Woronowicz C*-algebra, crossed product.

A submillimeter observation and study of star-forming regions

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Chinese Science Bulletin 2002年第1期47卷 16-21页

作者： JIANG Linhua, WU Yuefang & M. MillerDepartment of Astronomy, peking university, beijing 100871, China Chinese {3. of sciences-peking university joint beijing Astrophysics Center, beijing 100871, China I. Physikalisches Institut, Zulpicher Str Department of Astronomy Peking University Beijing China Chinese academy of sciences-peking {3. joint beijing Astrophysics Center Beijing China I. Physikalisches Institut Koeln 41 Germany

Using the 3.m radio telescope of KOSMA, we mapped 12CO (J = 3.2) lines for three molecular clouds, B3., S146 and TMC-2A. High-velocity molecular outflows are found in all these regions. The physical and dynamical pa-rameters of the outflows are derived, and their shapes and driving sources are analyzed. Contour maps of center veloci-ties show that the large scale systematic gradients exist in the three clouds. These observed motions are best explained by rotation after excluding the cause of outflows. Furthermore, in the core region of TMC-2A there is a velocity gradient in opposite direction from that of the large scale. It may be caused by magnetic braking. Finally, angular velocities of the clouds are calculated, and the effects of rotation against gravity and lowering the star-formation rate are also ana-lyzed.

关键词： dynamics of interstellar medium jets and outflows star formation.

INFINITE ELEMENT METHOD FOR THE EXTERIOR PROBLEMS OF THE HELMHOLTZ EQUATIONS

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Journal of Computational Mathematics 2000年第6期18卷 657-672页

作者： Lung-an Ying (School of Mathematical sciences, peking university, {3. 100871, China) 北京大学北京 100871

There are two cases of the exterior problems of the Helmholtz equation. If λ ≥ 0 the bilinear form is coercive, and if λ < 0 it is the scattering problem. We give a new approach of the infinite element method, which enables us to solve these exterior problems as well as corner problems. A numerical example of the scattering problem is given. [ABSTRACT FROM AUTHOR]

关键词： Helmholtz equation exterior problem infinite element method

Convergence analysis of the adaptive finite element method with the red-green refinement

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Science China Mathematics 2010年第2期53卷 499-512页

作者： ZHAO XuYing 1, 3., HU Jun 2,? & SHI ZhongCi 1 1 State Key Laboratory of Scientific and Engineering Computing, Institute of Computational Mathematics and Scientific/Engineering Computing, academy of Mathematics and Systems Science, Chinese academy of sciences, {3. 100190, China 2 Key Laboratory of Mathematics and Applied Mathematics (peking university), Ministry of Education and School of Mathematical sciences, peking university, {3. 100871, China 3.Graduate university of Chinese academy of sciences, {3. 100190, China State Key Laboratory of Scientific and Engineering Computing Institute of Computational Mathematics and Scientific/Engineering Computing Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing China Graduate university of Chinese academy of sciences Beijing China Key Laboratory of Mathematics and Applied Mathematics (peking university) Ministry of Education and School of Mathematical Sciences Peking University Beijing China

In this paper, we analyze the convergence of the adaptive conforming P 1 element method with the red-green refinement. Since the mesh after refining is not nested into the one before, the Galerkin-orthogonality does not hold for this case. To overcome such a difficulty, we prove some quasi-orthogonality instead under some mild condition on the initial mesh (Condition A). Consequently, we show convergence of the adaptive method by establishing the reduction of some total error. To weaken the condition on the initial mesh, we propose a modified red-green refinement and prove the convergence of the associated adaptive method under a much weaker condition on the initial mesh (Condition B).

关键词： red-green refinement adaptive finite element method convergence non-nested local refinement

Origin and Properties of Strong MgII Quasar Absorption Line Systems

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Chinese Journal of Astronomy and Astrophysics 2001年第1期1卷 21-28页

作者： Wei-Peng Lin and Zhen-Long Zou ( beijing Astronomical Observatory, Chinese academy of sciences, beijing 100012 CAS-peking university joint beijing Astrophysical Center, beijing 100871 Shanghai Astronomical Observatory,the Partner Group of MPI fur Astrop beijing Astronomical Observatory Chinese Academy of Sciences Beijing 100012 CAS-peking university joint {3. Astrophysical Center Beijing 100871 Shanghai Astronomical Observatory the Partner Group of MPI für Astrophysik Shanghai 200030

Strong MgII quasar absorption line systems provide us with a useful tool to understand the gas that plays an important role in galaxy formation. In this paper, placing the theories of galaxy formation in a cosmological context, we present semi-analytic models and Monte-Carlo simulations for strong MgII absorbers produced in gaseous galactic haloes and/or galaxy discs. We investigate the redshift path density for the MgII absorption lines and the properties of galaxy/absorber pairs, in particular the anti-correlation between the equivalent width of MgII absorption line and the projected galaxy-to-sightline distance. The simulated result of the mean redshift path density of strong MgII systems is consistent with the observational result. The fraction of strong MgII systems arising from galaxy disks is predicted to be ~ 10% of the total. There exists an anti-correlation between the absorption line equivalent and the projected distance of sightline to galaxy center and galaxy luminosity. We determined that the mean absorbing radius Rabs≈29 h-1 bpc(LB/LB*)0.3.. After taking selection effects into consideration, this becomes Rabs ≈3. h-1 bpc(LB/LB*)0.18, which is in good agreement with the observational result. This shows the importance of considering selection effects when comparing models with observations.

关键词： galaxies: formation-galaxies: fundamental parameters-galaxies: haloes- quasars: absorption lines