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Formation of Solar Delta Active Regions:Twist and Writhe of Magnetic Ropes

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chinese Journal of Astronomy and Astrophysics 2004年第6期4卷 563-577页

作者： Hong-QiZhang nationalastronomicalobservatories ChineseAcademyofSciencesBeijing100012

We analyze the process of formation of delta configuration in some well-known super active regions based on photospheric vector magnetogram observations. It is found that the magnetic field in the initial developing stage of some delta active regions shows a potential-like configuration in the solar atmosphere, the magnetic shear develops mainly near the magnetic neutral line with magnetic islands of opposite polarities, and the large-scale photospheric twisted field forming gradually later. Some results are obtained: (1) The analysis of magnetic writhe of whole active regions cannot be limited in the strong field of sunspots, because the contribution of the fraction of decayed magnetic field is non-negligible. (2) The magnetic model of kink magnetic ropes, supposed to be generated in the subatmosphere, is not consistent with the evolution of large-scale twisted photospheric transverse magnetic field and not entirely consistent with the relationship with magnetic shear in some delta active regions. (3) The proposition is that the large-scale delta active regions are formed from contribution by small-scale non-potential magnetic flux bundles generated in the subatmosphere.

关键词： sun activity sun flares sun magnetic fields

Entropy of Dilatonic Black Hole due to Arbitrary Spin Fields

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chinese Journal of Astronomy and Astrophysics 2001年第4期1卷 357-364页

作者： You-Gen Shen and Chang-Jun Gao (Shanghai astronomical Observatory, chinese academy of sciences, Shanghai 200030 national astronomical observatories, chinese academy of sciences, beijing 100012 Institute of Theoretical Physics, chinese academy of Scienc Shanghai astronomical Observatory Chinese Academy of Sciences Shanghai 200030 national astronomical observatories Chinese Academy of Sciences Beijing 100012 Institute of Theoretical Physics Chinese Academy of Sciences Beijing 100080

Using the membrane model based on the brick-wall model, we calculate the free energy and entropy of dilatonic black hole due to arbitrary spin fields. The result shows that the entropy of scalar field and the entropy ... 详细信息

关键词： black hole physics - entropy - spin

Solar Radio Bursts in the Period Oct. 22-Nov. 4, 2003

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chinese Journal of Astronomy and Astrophysics 2004年第3期4卷 205-208页

作者： Cheng-Ming Tan Qi-Jun Fu Yi-Hua Yan Yu-Ying Liu national astronomical observatories chinese academy of sciences beijing 100012 national astronomical observatories Chinese Academy of Sciences

A series of solar radio bursts were observed in AR NOAA 10486 with the SolarBroadband (1.1-7.6 GHz) Radio Spectrometers (SBRS of china). Here we analyze four significant eventsassociated with CME events and strong X-ray flares that occurred on 2003 October 22, 26, 27, *** Oct. 26 event is a long duration event (LDE) with drift pulsation structure (DPS), narrowbanddm-burst (DCIM), and more than seven types of Fine Structures (FSs); its time of the maximum flux(07:30 UT) is about half an hour later than the X-flare (06:54 UT).

关键词： sun: flares sun: radio radiation sun: fine structures

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 Joint beijing Astrophysics Center, Peking University, beijing 100871 national astronomical observatories Chinese Academy of Sciences

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

Do Globular Clusters Harbor Black Holes?

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chinese Journal of Astronomy and Astrophysics 2001年第4期1卷 291-295页

作者： Xian-Zhong Zheng (national astronomical observatories, chinese academy of sciences, beijing 100012)E-mail:zxz@*** national astronomical observatories Chinese Academy of Sciences

It has been firmly established that there exists a tight correlation be- tween the mass of the central black hole and velocity dispersion (or luminosity) in elliptical galaxies, 'pseudobulges' and bulges of galaxies, although the nature of this correlation still remains nuclear. We explore the possibility of extrapolating such a correlation to less massive, spherical systems like globular clusters. In particular, motivated by the apparent success in the globular cluster M15, we present an estimate of the central black hole mass for a number of globular clusters with available velocity dispersion data.

关键词： black hole physics-globular clusters: general - galaxies: general

A Test on Different Types of the Time Curve of Hardness Ratio of Gamma-Ray Bursts based on the Curvature Effect

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chinese Journal of Astronomy and Astrophysics 2008年第4期8卷 451-464页

作者： Lan-Wei Jia national astronomical observatories/Yunnan Observatory,chinese academy of sciences,Kunming 650011,china Graduate School of chinese academy of sciences,beijing 100049,china national astronomical observatories/ Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China Graduate School of chinese academy of sciences Beijing 100049 China

We analyzed a sample of 66 gamma-ray bursts （GRBs） and statistically confirmed the prediction on the time curve of the hardness ratio of GRBs made by Qin et al. based on the curvature effect. In their analysis, GRB pulses are divided into three types according to the shape of their raw hardness ratio （RHR） time curves, defined as to include the background counts to the signal counts, so as to make use of counts within small time intervals. Of the three types, very hard sources exhibit a perfect pulse-like profile （type 1）, hard bursts possess a pulse-like profile with a dip in the decay phase （type 2）, and soft bursts show no pulse-like profile but have only a dipped profile （type 3）. In terms of the conventional hardness ratio, type 3 sources are indeed generally softer than those of type 1 and type 2, in agreement with the prediction. We found that the minimum value of RHR is sensitive in distinguishing the different types. We propose that GRB pulses can be classified according to the minimum value of RHR and that the different type sources may be connected with different strengths of the shock or/and the magnetic field.

关键词： gamma-rays burst -- gamma-rays observations - methods statistical

An Efficient High-Resolution Shock-Capturing Scheme for Multi-Dimensional Flows I. Hydrodynamics

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chinese Journal of Astronomy and Astrophysics 2006年第6期6卷 680-688页

作者： Cong Yu national astronomical observatories / Yunnan astronomical Observatory, chinese academy of sciences, Kunming 650011 Graduate School of chinese academy of sciences, beijing 100049 national astronomical observatories / Yunnan astronomical Observatory Chinese Academy of Sciences Graduate School of chinese academy of sciences

Many problems at the forefront of theoretical astrophysics require a treatment of dynamical fluid behavior. We present an efficient high-resolution shock-capturing hydrodynamic scheme designed to study such phenomena. We have implemented a weighted, essentially non-oscillatory （WENO） scheme to fifth order accuracy in space, lILLE approximate Riemann solver is used for the flux computation at cell interface, which does not require spectral decomposition into characteristic waves and so is computationally friendly. For time integration we apply a third order total variation diminishing （TVD） Runge-Kutta scheme. Extensive testing and comparison with schemes that *** characteristic decomposition are carried out demonstrating the ability of our scheme to address challenging open questions in astrophysics.

关键词： accretion - hydrodynamics- method numerical - shock waves

Near-Infrared Imaging Observations of the Orion A-W Star Forming Region

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chinese Journal of Astronomy and Astrophysics 2002年第3期2卷 260-265页

作者： Jun-Jie Wangnational astronomical observatories, chinese academy of sciences, beijing 100012chinese academy of sciences-Peking University Joint beijing Astrophysics Center, beijing100871 national astronomical observatories Chinese Academy of Sciences Beijing 100012 Chinese Academy of Sciences-Peking University Joint Beijing Astrophysics Center Beijing 100871

We carried out near-infrared imaging observations of the Ori A-W region using the Italian 1.5 m TIRGO infrared telescope at Gornergrat. A group of infrared objects is visible on the K band image, including an IRAS source (IRS 1). From its IRAS flux density the IRAS luminosity is derived to be 45L⊙, which shows that IRS 1 is a low-mass protostar. By superimposing the position of the VLA H2O maser on the K image, we can identify the less evolved object IRS 1 as the excitation source of the H2O maser, within a projected distance of 470AU. This would be evidence that the maser effect is associated with the youngest phase of stellar evolution. The first probable HH object candidate in the Ori A-W region is discovered from the H2S(1)1-0 observation. Comparing the position of the H2O maser with the direction of the molecular hydrogen emission in the region, we suggest that the observed H2O maser could be tracing the circumstellar disk of IRS 1.

关键词： Stars: formation - ISM: jets and outflows

Information from the Kinematics of F and G Stars in the Solar Neighborhood

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chinese Journal of Astronomy and Astrophysics 2002年第5期2卷 419-428页

作者： Yu-Qin Chen, Gang Zhao and Jian-Rong Shinational astronomical observatories, chinese academy of sciences, beijing 100012 national astronomical observatories Chinese Academy of Sciences Beijing 100012

We have calculated the orbital parameters for 90 stars in Chen et al. and updated the kinematic data for stars in Edvardsson et al. by using the accurate Hipparcos parallaxes and proper motions, and recalculated the α-element abundances in Edvardsson et al. in a way consistent with Chen et al. The two sets of data are combined in a study of stellar populations and characteristics of F & G stars in the solar neighborhood. We confirm the result of Chen et al. that a distinguishable group of stars may belong to the thick disk rather than the thin disk. The ages for the stars are determined using the theoretical isochrones of VandenBerg et al. The age-metallicity relation is investigated for different subgroups according to distance from the sun and galactic orbital parameters. It is found that a mixing of stars with different orbital parameters significantly affect the age-metallicity relation for the disk. Stars with orbits confined to the solar circle all have metallicities [Fe/H] > -0.3 irrespective of their distances from the sun or from the Galactic plane.

关键词： stars: kinematics - Galaxy: evolution - Galaxy: solar neighborhood