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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 chinese academy of sciences-Peking University 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 (1.30 -±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

2MASS photometry and age estimation of the globular clusters in the outer halo of M31

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Research in Astronomy and Astrophysics 2012年第2期12卷 115-126页

作者： jun Ma 1,21 National astronomical observatories,chinese academy of sciences,beijing 100012,China 2 Key Laboratory of Optical Astronomy,National astronomical observatories,chinese academy of sciences,beijing 100012,China National astronomical observatories Chinese Academy of Sciences Beijing 100012 China Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China

We present the first photometric results in J, H and Ks from 2MASS （Two Micron All Sky Survey） imaging of 10 classical globular clusters （GCs） in the far outer regions of M31. Combined with the V and I photometric data from previous literature, we constructed a color-color diagram between J - Ks and V - Ⅰ. By comparing the integrated photometric measurements with evolutionary models, we estimate the ages of these clusters. The results showed that all of these clusters are older than 3 × 109 yr, and among them four are older than 10 Gyr and the other six have intermediate ages between 3 - 8 Gyr. The masses for these outer-halo GCs are from 7.0 × 104 M to 1.02 × 10^6 M. We argued that GC2 and GC3, whose ages, metallicities and distance moduli are almost the same, were accreted from the same satellite galaxy, if they did not form in situ. The statistical results show that the ages and metallicities of these 10 M31 outer-halo GCs do not vary with projected radial position, and a relationship between age and metallicity does not exist.

关键词： galaxies: halos - galaxies: individual (M31) - star clusters: general

A Method of Obtaining the Pitch Angle of Spiral Arms and the Inclination of Galactic Discs

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chinese Journal of Astronomy and Astrophysics 2001年第5期1卷 395-405页

作者： jun Ma (National astronomical observatories, chinese academy of sciences, beijing 100012) E-mail:majun@*** National astronomical observatories Chinese Academy of Sciences Beijing 100012

We investigate the mathematical form, the symmetry of spiral structure and the projected images of galactic discs. The measured pitch angles of spiral arms and inclination angles of galactic discs for 60 spiral galaxies are presented. The global spiral structure is emphasized in the study. It is found that, except for small-scale distortions, the spiral arms of those galaxies that were classified as AC 12 in the arm classification system of Elmegreen & Elmegreen, can be represented by the logarithmic spiral form.

关键词： galaxies: spiral galaxies - galaxies: spiral arm disc: inclination

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

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 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 Science Beijing 100012

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

What does the Sun tell and hint now?

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Research in Astronomy and Astrophysics 2009年第9期9卷 959-965页

作者： Ke-jun Li1,2 1 National astronomical observatories /Yunnan Observatory,chinese academy of sciences,Kunming 650011,China 2 Key Laboratory of Solar Activity,National astronomical observatories,chinese academy of sciences,beijing 100012,China National astronomical observatories/Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China Key Laboratory of Solar Activity National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China

Some historical records, which have held since the beginning of modern solar activity cycles, are being broken by the present Sun： cycle 23 records the longest cycle length and fall time; latitudes of high-latitude sunspots belonging to a new cycle around the minimum time of the cycle are statistically the lowest at present, compared with those of other cycles; there are only one or no sunspots in a month appearing at high latitudes for 58 months, which is the first time that such a long duration has been observed. The solar dynamo is believed to be slowing down due to：（1） the minimum smoothed monthly mean sunspot number is the smallest since cycle 16 onwards, and even probably among all modern solar cycles; and （2） once the time interval between the first observations of two neighboring sunspot groups is larger than 14 d, it should be approximately regarded as an observation of no sunspots on the visible solar disk, called a spotless event. Spotless events occur with the highest frequency around the minimum time of cycle 24, and the longest spotless event also appears around the minimum time for observations of the Sun since cycle 16. Cycle 24 is expected to have the lowest level of sunspot activity from cycle 16 onwards and even probably for all of the modern solar cycles.

关键词： Sun: activity -- Sun: general -- sunspots

A New Catalogue of Fine Structures Superimposed on Solar Microwave Bursts

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chinese Journal of Astronomy and Astrophysics 2004年第2期4卷 176-188页

作者： Qi-jun Fu, Yi-Hua Yan, Yu-Ying Liu, Min Wang and Shu-Juan WangNational astronomical observatories, chinese academy of sciences, beijing 100012 fuqijun2002@*** National astronomical observatories Chinese Academy of Sciences Beijing 100012

The 2.6-3.8 GHz, 4.5-7.5 GHz, 5.2-7.6 GHz and 0.7-1.5 GHz componentspectrometers of Solar Broadband Radio Spectrometer (SBRS) started routine observations,respectively, in late August 1996, August 1999, August 1999, and june 2000. They just managed tocatch the coming 23rd solar active maximum. Consequently, a large amount of microwave burst datawith high temporal and high spectral resolution and high sensitivity were obtained. A variety offine structures (FS) superimposed on microwave bursts have been found. Some of them are known, suchas microwave type Ⅲ bursts, microwave spike emission, but these were observed with more detail;some are new. Reported for the first time here are microwave type U bursts with similar spectralmorphology to those in decimetric and metric wavelengths, and with outstanding characteristics suchas very short durations (tens to hundreds ms), narrow bandwidths, higher frequency drift rates andhigher degrees of polarization. Type N and type M bursts were also observed. Detailed zebra patternand fiber bursts at the high frequency were found. Drifting pulsation structure (DPS) phenomenaclosely associated with CME are considered to manifest the initial phase of the CME, andquasi-periodic pulsation with periods of tens ms have been recorded. Microwave 'patches', unlikethose reported previously, were observed with very short durations (about 300 ms), very high fluxdensities (up to 1000 sfu), very high polarization (about 100% RCP), extremely narrow bandwidths(about 5%), and very high spectral indexes. These cannot be interpreted with the gyrosynchrotronprocess. A superfine structure in the form of microwave FS (ZPS, type U), consisting of microwavemillisecond spike emission (MMS), was also found.

关键词： sun: flares sun: radio radiation instrumentation: spectro-graphs

A Filament-Associated Halo Coronal Mass Ejection

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chinese Journal of Astronomy and Astrophysics 2001年第1期1卷 85-98页

作者： jun Zhang, Jingxiu Wang, and Nariaki Nitta ( beijing astronomical Observatory, National astronomical observatories,chinese academy of sciences, beijing 100012 Lockheed Martin Solar and Astrophysics Laboratory, Palo Alto, CA 94304, USA) Lockheed Martin Solar and Astrophysics Laboratory Palo Alto CA 94304 USA

There are only a few observations published so far that show the initiation of a coronal mass ejection (CME) and illustrate the magnetic changes in the surface origin of a CME. Any attempt to connect a CME with its local solar activities is meaningful. In this paper we present a clear instance of a halo CME initiation. A careful analysis of magnetograms shows that the only obvious magnetic changes in the surface region of the CME is a magnetic flux cancellation underneath a quiescent filament. The early disturbance was seen as the slow upward motion in segments of the quiescent filament. Four hours later, the filament was accelerated to about 50 km s-1 and erupted. While a small part of the material in the filament was ejected into the upper corona, most of the mass was transported to a nearby region. About forty minutes later, the transported mass was also ejected partially to the upper corona. The eruption of the filament triggered a two-ribbon flare, with post-flare loops connecting the flare ribbons. A halo CME, which is inferred to be associated with the eruptive filament, was observed from LASCO/C2 and C3. The halo CME contained two CME events, each event corresponded to a partial mass ejection of the filament. We suggest that the magnetic reconnection at the lower atmosphere is responsible for the filament eruption and the halo CME.

关键词： Sun: filament - Sun: magnetic fields-Sun: coronal mass ejection