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A Check on the Variations of Earth's Rotation with an Ancient Solar Eclipse

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chinese Journal of Astronomy and Astrophysics 2003年第6期3卷 569-575页

作者： Yan-Ben Han and Qi-Yuan Qiao national astronomical {2., chinese academy of sciences, beijing 100012 national astronomical {2. Chinese Academy of Sciences Beijing 100012

We address the relation between an ancient total eclipse, which occurred on A.D.1542.August 11 and the variation of Earth's rotation. The total eclipse was recorded in some ancient chinese books, especially in local chronicles. Some of the documents include useful information for determining the location of the totality zone. The parameters of the eclipse are calculated by using the DE406 Ephemeris. A high-precision value of ΔT which expresses the variation of the Earth's rotation, of about 300 ~ 380 s, is obtained.

关键词： solar eclipse earth rotation

Gamma-ray Bursts: a Probe of Black Holes

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chinese Journal of Astronomy and Astrophysics 2001年第6期1卷 487-493页

作者： Wei Wang and Yong-Heng Zhao national astronomical {2., chinese academy of sciences, beijing 100012 national astronomical {2. Chinese Academy of Sciences Beijing 100012

There is strong evidence for the existence of black holes (BHs) in some X-ray binaries and in most galactic nuclei based on different types of measurement, but black holes have not been definitely identified for the lack of very firm observational evidence up to now. Because direct evidence for BHs should come from determination of strong gravitational redshift, we expect an object can fall into the region near the BH horizon where radiation can be detected. Therefore the object must be a compact star such as a neutron star (NS), and intense astrophysical processes will release highly energetic radiation that is transient and fast-varying. These characteristics may point to the observed gamma-ray bursts (GRBs). Recent observations of iron lines suggest that afterglows of GRBs show properties similar to those observed in active galactic nuclei (AGNs), implying that the GRBs may originate from intense events related to black holes. A model for GRBs and after-glows is proposed here to obtain the range of gravitational redshifts (zg) of GRBs with known cosmological redshifts. Here, we provide a new method that, with a search for high-energy emission lines (X- or -γ-rays) in GRBs, one can determine the gravitational redshift. We expect zg to be 0.5 or even larger, so we can rule out the possibility of other compact objects such as NSs, and identify the central progenitors of GRBs as black holes.

关键词： black hole physics - accretion accretion disks - gamma rays: burst

A network flow algorithm to position tiles for LAMOST

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Research in Astronomy and Astrophysics 2009年第11期9卷 1277-1284页

作者： Guang-Wei Li and Gang Zhao national astronomical {2., chinese academy of sciences, beijing 100012. China national astronomical {2. Chinese Academy of Sciences Beijing 100012 China

We introduce the network flow algorithm used by the Sloan Digital Sky Survey （SDSS） into the sky survey of the Large sky Area Multi-Object fiber Spectroscopic Telescope （LAMOST） to position tiles. Because fibers in LAMOST＇s focal plane are distributed uniformly, we cannot use SDSS＇ method directly. To solve this problem, firstly we divide the sky into many small blocks, and we also assume that all the targets that are in the same block have the same position, which is the center of the block. Secondly, we give a value to limit the number of the targets that the LAMOST focal plane can collect in one square degree so that it cannot collect too many targets in one small block. Thirdly, because the network flow algorithm used in this paper is a bipartite network, we do not use the general solution algorithm that was used by SDSS. Instead, we give our new faster solution method for this special network. Compared with the Convergent Mean Shift Algorithm, the network flow algorithm can decrease observation times with improved mean imaging quality. This algorithm also has a very fast running speed. It can distribute millions of targets in a few minutes using a common personal computer.

关键词： methods data analysis -- methods statistical

Annual Modulation in Intraday Variability Timescales of Extragalactic Radio Sources

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chinese Journal of Astronomy and Astrophysics 2001年第2期1卷 133-143页

作者： Shan-Jie Qian and Xi-Zhen Zhang (beijing astronomical Observatory, {2. astronomical observatories, chinese academy of sciences, beijing 100012. beijing astronomical Observatory National Astronomical Observatories Chinese Academy of Sciences Beijing 100012

Annual modulations in timescales of intraday variability (IDV hereafter) are discussed for six extragalactic sources: 0716+714, 0917+62., 0954+65, 1749+70, 1803+78 and 2.07+77. The timescales calculated from scintillation theory are compared with the observational data . It is emphasized that systematic observations are required to identify the phenomenon and to determine the motion of the interstellar medium with respect to the Local Standard of Rest. In addition, significant deviations from the annual modulation could be due to intrinsic variations.

关键词： scattering - ISM: kinematics - BL Lacertae objects: individual: 0716+71 - quasars: individual: 0917+62.- radiation mechanisms: non-thermal

Discovery of an Optical Jet in the Rosette Nebula: Rosette HH2

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chinese Journal of Astronomy and Astrophysics 2003年第6期3卷 495-498页

作者： Jin-Zeng Linational astronomical {2., chinese academy of sciences, beijing 100012 national astronomical {2. Chinese Academy of Sciences Beijing 100012

We report on the discovery of an optical jet - Rosette HH2.- in the RosetteNebula. The jet system bears unique features for residing at the center of a giant HII region, andits energy source is visible with apparently very low extinction along the line of sight. Unlikemost other Herbig-Haro jets, this jet indicates a high-excitation origin, and its extended portionshows a seemingly intact structure, instead of normally a shocked working surface, which isattributed to photoablation.

关键词： stars: formation stars: pre-main sequence herbig-haro objects ISM: jetsand outflows

A method to predict amplitude and date of maximum sunspot number

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chinese Science Bulletin 2000年第14期45卷 1287-1290页

作者： HAN Yanbenbeijing astronomical Observatory,{2., national astronomical observatories,{2., beijing 100012. China beijing astronomical Observatory Chinese Academy of Sciences National Astronomical Observatories Chinese Academy of Sciences Beijing China

A method to predict the amplitude and date of the maximum sunspot number is introduced. The regression analysis of the relationship between the variation rate of monthly sunspot numbers in the initial stage of solar cycles and both of the maximum and the time-length of ascending period of the cycle showed that they are closely correlative. In general, the maximum will be larger and the ascending period will be shorter when the rate is larger. The rate of sunspot numbers in the initial 2.years of the 2.rd cycle is thus analyzed based on these grounds and the maximum of the cycle is predicted. For the smoothed monthly sunspot numbers, the maximum will be about 139.2.±18.8 and the time-length of ascending period will be about 3.31 ±0.42.years, that is to say, the maximum will appear around the spring of the year 2.00. For the mean monthly ones, the maximum will be near 170.1±2..9 and the time-length of ascending period will be about 3.42.±0.46 years, that is to say, the appearing date of the maximum

关键词： solar activity prediction sunspot number 2.rd solar cycle.

IRAS 01005+7910:a High Galactic Latitude Post-AGB Star

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chinese Journal of Astronomy and Astrophysics 2002年第3期2卷 193-196页

作者： Jing-Yao Hunational astronomical {2., chinese academy of sciences, beijing 100012 national astronomical {2. Chinese Academy of Sciences Beijing 100012

IRAS 01005+7910 is a cold IRAS source. We present its optical identification, photometric and spectroscopic observation results. Its optical counterpart is classified as a B2.e star with V magnitude 10.85. Its Hα line shows the P Cygni profile. According to its location in the Galaxy (b = 16.6), we consider it to be a post-AGB star or a proto-planetary nebula.

关键词： stars: post-AGB - infrared: stars - stars: evolution

Spectroscopic study of globular clusters in the halo of M31 with the Xinglong 2.16 m telescope

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Research in Astronomy and Astrophysics 2011年第11期11卷 1298-1310页

作者： Zhou Fan1,2.Ya-Fang Huang1,2.Jin-Zeng Li1,2.Xu Zhou1,2.Jun Ma1,2.Hong Wu1,2.Tian-Meng Zhang1,2.and Yong-Heng Zhao1,2.1 national astronomical {2.,chinese academy of sciences,beijing 100012.China 2.Key Laboratory of Optical Astronomy,national astronomical {2.,chinese academy of sciences,beijing 100012.China national astronomical {2. Chinese Academy of Sciences Beijing 100012 China Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China

We present spectroscopic observations for 11 confirmed globular clusters(GCs) of M31 with the OMR spectrograph on the 2.16 m telescope at the Xinglong site of national astronomical {2.,chinese academy of *** of our sample clusters are located in the halo of M31 and the most remote one is out to a projected radius of 78.75 kpc from the galactic *** all our sample clusters,we measured the Lick absorption-line indices and radial *** is noted that most GCs in our sample are distinct from the HI rotation curve of galaxy M31,especially for B514,MCGC5,H12.and B517,suggesting that most of our sample clusters do not have a kinematic association with the star-forming young disk of the *** separately fitted the absorption line indices from the updated stellar population model of Thomas et *** two different tracks of Cassisi and Padova,by applying the χ2.minimization *** fitting results show that all our sample clusters are older than 10 Gyr,and metal-poor(2.38 ≤ [Fe/H] ≤ 0.91 dex).After merging the spectroscopic metallicity of our work with the previously published ones,we extended the cluster sample out to a projected radius of 117 kpc from the galaxy's *** found the metallicity gradient exists for all the confirmed clusters with a slope of 0.02. ± 0.001 dex kpc ***,the slope turns out to be 0.018 ± 0.001 dex kpc 1 for all the halo clusters,which is much *** we only consider the outer halo clusters with rp > 2. kpc,the slope becomes 0.010 ± 0.002.dex kpc 1 and if one cluster G001 is excluded from the outer halo sample,the slope is 0.004 ± 0.002.dex kpc ***,we conclude that the metallicity gradient for M31's outer halo clusters is not significant,which agrees well with previous findings.

关键词： galaxies individual(M31) — galaxies star clusters — globular clusters general — star clusters general

Inhomogeneity in Spectral Transmission of the Coated UB VRI Filters of BFOSC and its Influence on Photometry

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chinese Journal of Astronomy and Astrophysics 2002年第6期2卷 563-575页

作者： Bao-An Yao and Liu Huang1 Shanghai astronomical Observatory, chinese academy of sciences, Shanghai 2.0030{2., chinese academy of sciences, beijing 100012 national astronomical {2. Chinese Academy of Sciences Beijing 100012

In order to realize the Johnson UBV and Kron-Cousins RI photometric systems in BFOSC, glass filters were purchased according to the Bessell prescription. All the filters are anti-reflection coated,on both sides to increase the transmission. By comparing two dome flat-field exposures taken through any one of these filters set in two orientations 90degrees apart, inhomogeneities in the filter transmission is clearly demonstrated. Using a PDS microphotometer, we have confirmed that the form of their spectral transmission curve varied from point to point on the filters. This kind of inhomogeneity cannot be eliminated by dividing by flat-fielding exposure and must be ascribed to inhomogeneities in the coating. This is not some accidental defect in coating, it is in the existing coating technique because all the filters (including the narrow-band interference ones) for the BFOSC and a Hbeta filter made by another manufacturer showed a similar pattern. We found that for the studies of variable stars with amplitudes less than 0.05 mag. or studies aiming at establishing accurate C-M diagrams of star clusters, the usual uncoated Schott glass filters of Bessell's prescription are to be preferred.

关键词： methods : data analysis techniques : photometric