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A GRB Follow-up System at the Xinglong Observatory and Detection of the High-Redshift GRB 060927

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Chinese Journal of Astronomy and Astrophysics 2008年第6期8卷 693-699页

作者： Wei-Kang Zheng Jin-Song Deng Meng Zhai Li-Ping Xin Yu-Lei Qiu Jing Wang Xiao-Meng Lu Jian-Yan Wei Jing-Yao Hu national astronomical observatories Chinese Academy of Sciences Beijing 100012 China Graduate School of Chinese Academy of Sciences Beijing 100049 China

A gamma-ray burst （GRB） optical photometric follow-up system at the Xinglong Observatory of national astronomical observatories of China （NAOC） has been constructed. It uses the 0.8-m Tsinghua-NAOC Telescope （TNT） and the 1-m EST telescope, and can au- tomatically respond to GRB Coordinates Network （GCN） alerts. Both telescopes slew relatively fast, being able to point to a new target field within - 1 min upon a request. Whenever available, the 2.16-m NAOC telescope is also used. In 2006 the system responded to 15 GRBs and detected seven early afterglows. In 2007 six GRBs have been detected among 18 follow- up observations. TNT observations of the second most distant GRB 060927 （z = 5.5） are shown, which started as early as 91 s after the GRB trigger. The afterglow was detected in the combined image of the first 19 × 20 s unfiltered exposures. This GRB follow-up system has joined the East-Asia GRB Follow-up Observation Network （EAFON）.

关键词： gamma-rays： bursts gamma-rays： observations telescopes

Ionization state of cosmic hydrogen by early stars and quasars

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Research in Astronomy and Astrophysics 2009年第6期9卷 665-681页

作者： Xiao-Chun Mao1,2 1 national astronomical observatories, Chinese Academy of Sciences, Beijing 100012, China 2 Graduate University of Chinese Academy of Sciences, Beijing 100049, China national astronomical observatories Chinese Academy of Sciences Beijing 100012 China Graduate University of Chinese Academy of Sciences Beijing 100049 China

Cosmic hydrogen is reionized and maintained in its highly ionized state by the ultraviolet emission attributed to an early generation of stars and quasars. The Lyα opacity observed in absorption spectra of high-redshift quasars permits more stringent constraints on the ionization state of cosmic hydrogen. Based on density perturbation and structure formation theory, we develop an analytic model to trace the evolution of the ionization state in the post-overlap epoch of reionization, in which the bias factor is taken into account. For quasars, we represent an improved luminosity function by utilizing a hybrid approach for the halo formation rate that is in reasonable agreement with the published measurements at 2 ≤ z ≤ 6. Comparison with the classic Press-Schechter mass function of dark matter halos, we demonstrate that the biased mass distribution indeed enhances star formation efficiency in the overdense environment by more than 25 per cent following the overlap of ionized bubbles. In addition, an alternative way is introduced to derive robust estimates of the mean free path for ionizing photons. In our model, star-forming galaxies are likely to dominate the ionizing background radiation beyond z = 3, and quasars contribute equally above a redshift of z ～ 2.5. From 5 ≤ z ≤ 6, the lack of evolution in photoionization rate can thus be explained by the relatively flat evolution in star formation efficiency, although the mean free path of ionizing photons increases rapidly. Moreover, in the redshift interval z ～ 2 - 6, the expected mean free path and Gunn-Peterson optical depth obviously evolve by a factor of ～ 500 and ～50 respectively. We find that the relative values of critical overdensities for hydrogen ionization and collapse could be 430% at z ≈2 and 2% at z ≈6, suggesting a rapid overlap process in the overdense regions around instant quasars following reionization. We further illustrate that the absolute estimates of the fraction of neutral hydrogen computed from theoretical models may not be important becau

关键词： cosmology theory -- formation galaxies -- quasars general -- diffuse radiation -- intergalactic medium

Spectroscopic and photometric observations of unidentified ultraviolet variable objects in the GUVV-2 Catalog

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Research in Astronomy and Astrophysics 2011年第7期11卷 833-842页

作者： You Li Jing Wang Jian-Yan Wei Xiang-Tao He Department of Astronomy Beijing Normal University Beijing 100875 China national astronomical observatories Chinese Academy of Sciences Beijing 100012 China

An NUV-optical diagram composed from sources from the second Galaxy Evolution Explorer（GALEX） Ultraviolet Variability（GUVV-2） Catalog provides us with a method to tentatively classify the unknown GUVV-2 sources by their NUV-optical magnitudes.For the purpose of testing the correctness and generality of the method,we carry out a program on the spectroscopic observations of the unidentified GUVV-2 sources.The spectroscopic identification of these 37 sources are 19 type-A to-F stars,10 type-G to-K stars and 7 M dwarf stars together with an AGN.We also present the light curves in the R-band for two RR Lyrae star candidates selected from the NUV-optical diagram,both of which undergo cyclic variations.Combining their light curves and colors,we classify them as RR Lyrae stars.To confirm the re-sults,we show a color-color diagram for the 37 newly identified spectroscopic objects compared with previously identified ones,which are consistent with our previous re-sults,indicating that the ultraviolet variable sources can initially be classified by their NUV/optical color-color diagram.

关键词： stars：variables：general—galaxies：active—methods：observational—ultraviolet emission

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) Beijing astronomical Observatory National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 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

An orbital period investigation of the Algol-type eclipsing binary VW Hydrae

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Chinese Journal of Astronomy and Astrophysics 2009年第3期9卷 307-314页

作者： Jia Zhang Sheng-Bang Qian Boonrucksar Soonthomthum national astronomical observatories/Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China Graduate School of the Chinese Academy of Sciences Beijing 100039 China national astronomical Research Institute of Thailand/Ministry of Science and Technology Bangkok Thailand

Orbital period variations of the Algol-type eclipsing binary, VW Hydrae, are analyzed based on one newly determined eclipse time and the other times of light minima collected from the literature. It is discovered that the orbital period shows a continuous increase at a rate ofdP/dt = ＋6.34 × 10^-7 d yr^-1 while it undergoes a cyclic change with an amplitude of 0.0639 d and a period of 51.5 yr. After the long-term period increase and the large-amplitude period oscillation were subtracted from the O-C curve, the residuals of the photoelectric and CCD data indicate a small-amplitude cyclic variation with a period of 8.75 yr and a small amplitude of 0.0048 d. The continuous period increase indicates a conservative mass transfer at a rate of dM2/dt = 7.89 × 10^-8 M⊙ yr^-1 from the secondary to the primary. The period increase may be caused by a combination of the mass transfer from the secondary to the primary and the angular momentum transfer from the binary system to the circumbinary disk. The two cyclic period oscillations can be explained by light-travel time effects via the presence of additional bodies. The small-amplitude periodic change indicates the existence of a less massive component with mass M3 〉 0.53 M⊙, while the large-amplitude one is caused by the presence of a more massive component with mass M4 〉 2.84M⊙. The ultraviolet source in the system reported by Kviz ＆ Rufener （1987） may be one of the additional components, and it is possible that the more massive one may be an unseen neutron star or black hole. The rapid period increase and the possibility of the presence of two additional components in the binary make it a very interesting system to study. New photometric and high-resolution spectroscopic observations and a detailed investigation of those data are required in the future.

关键词： stars binaries close - stars binaries eclipsing - multiple stars - stars individual （VW Hya）

The global image of the Moon obtained by the Chang'E-1:Data processing and lunar cartography

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Science China Earth Sciences 2010年第8期53卷 1091-1102页

作者： LI ChunLai1, LIU JianJun1, REN Xin1, MOU LingLi1, ZOU YongLiao1, ZHANG HongBo1, Lü Chang1, LIU JianZhong1, ZUO Wei1, SU Yan1, WEN WeiBin1, BIAN Wei1, ZHAO BaoChang2, YANG JianFeng2, ZOU XiaoDuan1, WANG Min1, XU Chun1, KONG DeQing1, WANG XiaoQian1, WANG Fang1, GENG Liang1, ZHANG ZhouBin1, ZHENG Lei1, ZHU XinYing1, LI JunDuo1 & OUYANG ZiYuan11 national astronomical observatories, Chinese Academy of Sciences, Beijing 100012, China 2 Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an 710119, China national astronomical observatories Chinese Academy of Sciences Beijing China Xi’an Institute of Optics and Precision Mechanics Chinese Academy of Sciences Xi’an China

The global lunar image of the first phase of Chinese Lunar Exploration Program is the first image that covered all over the surface of the Moon. It will serve as a critical foundation for succeeding exploration and scientific research. In this paper, the acquisition, characteristics, and data quality of Chang'E-1 CCD image data are described in detail. Also described are the methodology and procedure of data processing. According to rule of planetary cartography, the image data have been processed, geometrically corrected, and then mosaicked and merged in a scale of 1:2.5 million. The results of data processing and charting show that the image data of Chang'E-1 CCD and their geometric precision meet the demand of charting a map in the scale of 1:2.5 million. The relative geometric positioning precision of the global image is better than 240 m, and the absolute geometric positioning precision is slightly better than that of the ULCN2005 and Clementine lunar basemap (V2.0). The plane positioning precision is approximately 100-1500 m. This global image proves to be the best global image of the Moon so far in terms of space coverage, image quality, and positioning precision.

关键词： Chang’E-1 lunar CCD data processing lunar image position lunar global image

astronomical Test with CMOS on the 60 cm Telescope at the Xinglong Observatory,NAOC

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Research in Astronomy and Astrophysics 2024年第5期24卷 85-102页

作者： Hai-Yang Mu Zhou Fan Yi-Nan Zhu Yu Zhang Hong Wu Key Laboratory of Optical Astronomy National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101People’s Republic of China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049People’s Republic of China

This work shows details of an evaluation of an observational system comprising a complementary metal-oxidesemiconductor detector, 60 cm telescope and filter complement. The system’s photometric precision and differential photometric precision, and extinction coefficients were assessed through observations of Supersky flat fields, open clusters, standard stars and exoplanets. Photometry was precision achieved at the 0.02 mag level, with differential photometry of 0.004 mag precision. Extinction was found to agree with previous studies conducted at Xinglong Observatory. Ultimately, the results demonstrate this observing system is capable of precision scientific observations with a charge-coupled device across the optical wavelengths.

关键词： atmospheric effects-instrumentation detectors-techniques polarimetric-stars atmospheres-eclipses

Polar Coronal Holes During Solar Cycles 22 and 23

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Chinese Journal of Astronomy and Astrophysics 2005年第5期5卷 531-538页

作者： Jun Zhang J. Woch S. Solanki national astronomical observatories Chinese Academy of Sciences Beijing 100012 Max-Planck-Institut fiir Sonnensystemforschung Katlenburg-Lindau D-37191 Germany

Data from the Solar Wind Ion Composition Spectrometer （SWICS） on Ulysses and synoptic maps from Kitt Peak are used to analyze the polar coronal holes of solar activity cycles 22 and 23 （from 1990 to end of 2003）. In the beginning of the declining phase of solar cycles 22 and 23, the north polar coronal holes （PCHs） appear about one year earlier than the ones in the south polar region. The solar wind velocity and the solar wind ionic charge composition exhibit a characteristic dependence on the solar wind source position within a PCH. From the center toward the boundary of a young PCH, the solar wind velocity decreases, coinciding with a shift of the ionic charge composition toward higher charge states. However, for an old PCH, the ionic charge composition does not show any obvious change, although the latitude evolution of the velocity is similar to that of a young PCH.

关键词： Sun： coronal - Sun： particle emission - Sun： solar wind

Dynamical Dark Energy in Light of Cosmic Distance Measurements. Ⅰ.A Demonstration Using Simulated Datasets

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Research in Astronomy and Astrophysics 2024年第6期 9-16页

作者： Gan Gu Xiaoma Wang Xiaoyong Mu Shuo Yuan Gong-Bo Zhao national astronomical observatories Chinese Academy of Sciences University of Chinese Academy of Sciences Institute for Frontiers in Astronomy and Astrophysics Beijing Normal University

We develop methods to extract key dark energy information from cosmic distance measurements including the BAO scales and supernova(SN) luminosity distances. Demonstrated using simulated data sets of the complete DESI, LSST and Roman surveys designed for BAO and SN distance measurements, we show that using our method, the dynamical behavior of the energy, pressure, equation of state(with its time derivative) of dark energy and the cosmic deceleration function can all be accurately recovered from high-quality data, which allows for robust diagnostic tests for dark energy models.

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