2004, Vol.4, No.4 (August 20, 2004)


Contents

RESEARCH PAPERS
Extragalactic Astronomy
  • UBVI Surface Photometry of the Spiral Galaxy NGC 300 in the Sculptor Group    p.299
    Sang Chul Kim, Hwankyung Sung,Hong Soo Park  and Eon-Chang Sung  
    Abstract | | PDF file (780 KB) | PS file *.gz  (1086 KB) 
  • The Synchrotron Emission of Jets with Transverse Velocity Discrepancy    p.311
    Hui-Quan Li, Jian-Cheng Wang and Li Xue  
    Abstract | | PDF file (223 KB) | PS file *.gz  (243 KB) 
Stars
  • Spin Evolution of Neutron Stars in OB/X-ray Binaries    p.320
    Fan Zhang, Xiang-Dong Li and Zhen-Ru Wang 
    Abstract | | PDF file (348 KB) | PS file *.gz  (384 KB) 
  • Time-dependent Behaviour of the Low Amplitude $\delta$ Scuti Star HD 52788   p.335
    Ai-Ying Zhou
    Abstract | | PDF file (244 KB) | PS file *.gz  (342 KB)  
  • Golden Ratio Sinusoidal Sequences and the Multimode Pulsation of the $\delta$ Sct Star V784 Cassiopeiae   p.343
    Juan Garcia Escudero
    Abstract | | PDF file (217 KB) | PS file *.gz  (413 KB)  
  • The Role of T50 in the Classification of Gamma-ray Bursts   p.349
    Xiao-Hong Zhao, Yi-Ping Qin, Yun-Ming Dong and Zhao-Yang Peng
    Abstract | | PDF file (403 KB) | PS file *.gz  (702 KB)  
The Sun
  • On the Positronium Continuum and 0.511 MeV Line in Solar Flares   p.357
    Wei-Qun Gan, Jin Chang, You-Ping Li, Yang Su and L. I. Miroshnichenko
    Abstract | | PDF file (166 KB) | PS file *.gz  (133 KB)  
  • Calibration of Vector Magnetogram with the Nonlinear Least-squares Fitting Technique   p.365
    Jiang-Tao Su and Hong-Qi Zhang
    Abstract | | PDF file (783 KB) | PS file *.gz  (923 KB)  

 

  • Unusually Broadened Spectral Profiles Observed in Solar Prominences   p.377
    Hui Li, Jian-Qi You and Eijiro Hiei
    Abstract | | PDF file (1043 KB) | PS file *.gz  (7271 KB)  
Instruments, Observational Techniques and Data Processing
  • Upgrade Procedure for the Delingha 13.7-m Telescope   p.390
    Ying-Xi Zuo, Ji Yang, Sheng-Cai Shi, Shan-Huai Chen, Li-Ben Pei, Qi-Jun Yao, Jin-Jiang Sun and Zhen-Hui Lin
    Abstract | | PDF file (292 KB) | PS file *.gz  (301KB)  
  • A Performance Study of the CCD Cameras of the Joint Laboratory of Optical Astronomy   p.397
    Bao-An Yao, Chun-Sheng Zhang and Qing Lin
    Abstract | | PDF file (1373KB) | PS file *.gz  (2831 KB)  

 


Abstract

 


UBVI Surface Photometry of the Spiral Galaxy NGC 300 in the Sculptor Group 

Sang Chul Kim (1), Hwankyung Sung (2), Hong Soo Park (3) and Eon-Chang Sung (1) 

Affiliation:    (1) Korea Astronomy Observatory, Taejon 305-348, Republic of Korea; sckim@kao.re.kr 
                     (2) Department of Astronomy and Space Science, Sejong University, 98 Gunja-dong, Gwangjin-gu, Seoul 143-747, Republic of Korea
                     (3) Astronomy Program, SEES, Seoul National University, Seoul 151-742, Republic of Korea
 
E-mail:    sckim@kao.re.kr    (corresponding author)

Abstract

We present  UBVI surface photometry over a 20.5' × 20.5' area of the late-type spiral galaxy NGC 300. We have derived isophotal maps, surface brightness profiles, ellipticity profiles, position angle profiles, and color profiles. By merging our I-band measurements with those of Böker et al. based on Hubble Space Telescope observations, we have obtained combined I-band surface brightness profiles for the region 0.02'' < r < 500'' and have decomposed the profiles into three components: a nucleus, a bulge, and an exponential disk.

Key words: galaxies: spiral --- galaxies: photometry --- galaxies: individual (NGC 300) --- galaxies: nuclei

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The Synchrotron Emission of Jets with Transverse Velocity Discrepancy 

Hui-Quan Li (1,2,3), Jian-Cheng Wang (1,2) and Li Xue (1,2,3)

Affiliation:   (1)  National Astronomical Observatories, Yunnan Observatory, Chinese Academy of Sciences, Kunming 650011; li_huqu@sohu.com 
                    (2)  United Laboratory for Optical Astronomy, Chinese Academy of Sciences
                    (3)  Graduate School of the Chinese Academy of Sciences

E-mail:   li_huqu@sohu.com   (corresponding author)

Abstract

It has been commonly accepted that the bulk velocity of extragalactic jets varies in all directions. We examined the synchrotron radiation of a jet with velocity structure in the direction perpendicular to its axis and found that the spectral energy distribution (SED) is not strongly influenced by this circumstance, that there is only a small increase in the emission intensity and almost no shift in the peak frequency. For objects with smaller inclined angles $\theta _0$ between the jet axis and the line of our sight, such as Blazars, the effect is more important. When $\theta _0$ exceeds a critical value there is no longer any change in the SED. To compare the bulk speed with different velocity structure, an equivalent speed $\langle \beta \rangle $ is defined which would reproduce the same spectral profile. There possibly exists a stress $f_\mu (y)$ between layers of the outflow when the velocity is not the same in the jet.

Key words:  galaxies: jets --- radiation mechanisms: non-thermal --- methods: numerical

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Spin Evolution of Neutron Stars in OB/X-ray Binaries

Fan Zhang, Xiang-Dong Li and Zhen-Ru Wang

Affiliation:    National Astronomical Observatories, CAS (NAOC), Beijing 100012, China
               
E-mail:   zfastro@nju.edu.cn   (corresponding author)

Abstract

We have investigated the relation between the orbital period Porb and the spin period Ps of neutron stars in OB/X-ray binaries. By simulating the time-development of the mass loss rate and radius expansion of a 20$M_{\odot}$ donor star, we have calculated the detailed spin evolution of the neutron star before steady wind accretion occurs (that is, when the break spin period is reached), or when the OB star begins evolving off the main sequence or has filled its Roche lobe. Our results are compatible with the observations of OB/X-ray binaries. We find that in relatively narrow systems with orbital periods less than tens of days, neutron stars with initial magnetic field B0 stronger than about 3×1012 G can reach the break spin period to allow steady wind accretion in the main sequence time, whereas neutron stars with B0 < 3×1012 G and/or in wide systems would still be in one of the pulsar, rapid rotator or propeller phases when the companion evolves off the main sequence or fills its Roche lobe. Our results may help understand the various characteristics of the observed OB/neutron star binaries along with their distributions in the Ps-Porb diagram.

Key words:  binaries: close -- stars: evolution -- stars: pulsars -- stars: supergiants -- stars: winds, outflows

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Time-dependent Behaviour of the Low Amplitude $\delta$ Scuti Star HD 52788

Ai-Ying Zhou

Affiliation:    National Astronomical Observatories, CAS (NAOC), Beijing 100012, China
                   
E-mail:    aiying@bao.ac.cn    

Abstract

Wavelet transform is applied to reanalyze the low amplitude $\delta$ Scuti star HD 52788, which exhibits complex light variations with uncertain frequency solutions. We gain an insight into the strong instability of pulsation present in the star. Based on an estimate of the star's physical parameters, its evolutionary status is determined. An attempt of asteroseismic modelling failed to predict the observed dense frequencies. Because of its varying pulsation spectrum, HD 52788 is a distinctive and very interesting object among $\delta$ Sct stars for testing current models of stellar evolution and pulsation.

Key words:  methods: data analysis --- stars: oscillations --- $\delta$ Scuti --- stars: individual (HD 52788)

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Golden Ratio Sinusoidal Sequences and the Multimode Pulsation of the $\delta$ Sct Star V784 Cassiopeiae

Juan Garcia Escudero


Affiliation:   Departamento de Fisica, Universidad de Oviedo, 33007-Oviedo Spain

E-mail:      jjge@pinon.ccu.uniovi.es    (corresponding author)
  
Abstract

Non periodic ordered sequences obtained by production rules in formal grammars are applied to the analysis of the multi-periodicity of the $\delta$ Scuti type variable star V784 Cas. An artificial light curve for V784 Cas is generated by a non deterministic derivation in a context-sensitive grammar by concatenation of two sinusoidal fragments following certain word sequences. The two basic building blocks represent temporal segments in a golden ratio and the number of long and short segments in a word are also in a golden ratio.

Key words:   stars: variables:  $\delta$ Scuti --- stars: individual: V784 Cas

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The Role of T50 in the Classification of Gamma-ray Bursts

Xiao-Hong Zhao, Yi-Ping Qin, Yun-Ming Dong and Zhao-Yang Peng

Affiliation:    Yunnan Observatory, Chinese Academy of Sciences, Kunming 650011     
                    
E-mail:    agns00@public.km.yn.cn      (corresponding author)

Abstract

The role of T50 in classifying gamma-ray bursts (GRBs) is investigated. We take T50=0.7 s as the line of division and find that some bursts belonging to the class of long bursts defined by T90 $\geq$ 2 s now become short bursts (sample 1), while some belonging to the class of short bursts defined by T90 < 2 s now become long bursts (sample 2). We study how these sources are affected by the two methods of classification and find the change of classes of sample 1 is due to some peculiar properties of the light curves. Based on their characters, most of the bursts of sample 1 should be taken as short bursts.

Key words:  gamma ray: bursts --- gamma ray: observations

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On the Positronium Continuum and 0.511 MeV Line in Solar Flares

Wei-Qun Gan (1), Jin Chang (1), You-Ping Li (1), Yang Su (1) and L. I. Miroshnichenko (2)

Affiliation:    (1) Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008; 
                     (2)  IZMIRAN, Troitsk, Moscow Region, 142190, Russia
E-mail:     wqgan@mail.pmo.ac.cn     (corresponding author)

Abstract

We have studied the influence of the density of the annihilation region on the positronium continuum. A relation between the ratio 3$\gamma$/2$\gamma$ and the density is explicitly given, with which one can derive directly from the observed 3$\gamma$/2$\gamma$ the density where the annihilation occurs. A unique solution may be found from the observed width of the 0.511 MeV line. We applied the method to three flares observed by GRS/SMM. It is shown that due to the measuring uncertainties in the 0.511 MeV line width, we cannot distinguish a chromospheric source from a coronal source, though both accurately localized. To improve the measuring accuracy of the 0.511 MeV line and the ratio 3$\gamma$/2$\gamma$ will be an important step for a better understanding of the annihilation process in solar flares.

Key words:  Sun: flares --- Sun: X-rays, gamma-rays

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Calibration of Vector Magnetogram with the Nonlinear Least-squares Fitting Technique

Jiang-Tao Su and Hong-Qi Zhang

Affiliation:     National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012
                    
E-mail:    sjt@sun10.bao.ac.cn     (corresponding author)

Abstract

To acquire Stokes profiles from observations of a simple sunspot with the Video Vector Magnetograph at Huairou Solar Observing Station (HSOS), we scanned the FeI $\lambda$ 5324.19 Å line over the wavelength interval from 150 mÅ redward of the line center to 150 mÅ blueward, in steps of 10 mÅ. With the technique of analytic inversion of Stokes profiles via nonlinear least-squares, we present the calibration coefficients for the HSOS vector magnetic magnetogram. We obtained the theoretical calibration error with linear expressions derived from the Unno-Becker equation under weak-field approximation.

Key words:   Sun: activity --- Sun: magnetic fields --- sunspots

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Unusually Broadened Spectral Profiles Observed in Solar Prominences

Hui Li (1), Jian-Qi You (1) and Eijiro Hiei (2)

Affiliation:  (1) Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008;
                   (2)  National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan
                    
E-mail:     lihui@mail.pmo.ac.cn    (corresponding author)

Abstract

After surveying the spectra of 39 prominences observed by the Multi-channel Infrared Solar Spectrograph at Purple Mountain Observatory and the 25 cm coronagraph at the Norikura Solar Observatory, we found that about 28% of them show small spatial scale (6''--8'') and short time scale (tens of seconds to a few minutes), unusual large broadening and large shift velocities in spectral lines including $H\alpha$, $H\beta$, $H\epsilon$, Ca II H, Ca II K, Ca II 8542Å, He I D3 and He I 10830Å. We present in detail two typical events observed respectively on 2002 May 27 and 1981 August 2. The full-width at half maximum of the widest profile of the 2001 prominence is 1.8Å for $H\alpha$ and 2.9 Å for He I 10830Å, while that of the 1981 prominence is 5.3 Å for $H\beta$, 3.6 Å for Ca II K, 4.0 Å for Ca II H and 2.8 Å for He I D3. Such broadenings generally occur at a level of several-thousand kilometres above the chromosphere. Further, most of these prominences manifest a rotation of (0.4--1.35)×10-2 rads s-1 pointing to the Sun and large line-of-sight velocities of 20--200 km s-1. Some of these events correspond in time to an enhancement or a small peak in the GOES X-ray flux, indicating the existence of high energy process at work. These prominences generally display discernible changes in the $H\alpha$ morphology around the time of large broadening, but do not show $H\alpha$ brightening or overall eruption except for a few small surge-like events, hence, they are hardly observed in daily $H\alpha$ patrols. According to the characteristics of their $H\alpha$ structures and spectral properties, we infer these events are small-scale eruptions similar to nano-flares, which may contribute to the mass and energy transported into the corona. Large turbulent velocities of 25--120 km s-1 are responsible for the observed broadenings.

Key words:  Sun: prominences --- line: profiles --- turbulence

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Upgrade Procedure for the Delingha 13.7-m Telescope

Ying-Xi Zuo, Ji Yang, Sheng-Cai Shi, Shan-Huai Chen, Li-Ben Pei, Qi-Jun Yao, Jin-Jiang Sun and Zhen-Hui Lin

Affiliation:  Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008
                    
E-mail:    yxzuo@pmodlh.ac.cn         (corresponding author)

Abstract

The 13.7-m millimeter-wave radio telescope of Purple Mountain Observatory operates at 3200-m above the sea level near Delingha, Qinghai Province, China. Equipped with a superconducting SIS receiver, the telescope is used in the millimeter-wave band ranging from 85 to 115 GHz. An upgrade procedure is reported here which includes a superconducting SIS receiver, a new phase-locked local oscillator, a dedicated multi-line backend system, and a new control system based on industrial computer with PCI bus. With the dedicated multi-line backend system, the CO and isotopic lines around 110 GHz are obtained simultaneously. In recent years, scientific activities with this telescope have been focused on studies of Galactic molecular clouds and star formation regions, including surveys of molecular lines from IRAS sources and large-scale map of molecular clouds. Other programs include studies of the circumstellar envelope of late-type stars and interaction of Galactic supernova remnants with dense molecular gas.

Key words:  telescopes: radio telescope --- millimeter wavelength astronomy --- instrument

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A Performance Study of the CCD Cameras of the Joint Laboratory of Optical Astronomy

Bao-An Yao (1), Chun-Sheng Zhang (2) and Qing Lin (1)

Affiliation:   (1) Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030
                    (2) Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008
                      
E-mail:    yba@shao.ac.cn    (corresponding author)

Abstract

A performance study of several CCD cameras of the Chinese Joint Laboratory of Optical Astronomy (CJLOA) is presented. The main results are: 1) We propose a modified classical method to analyse the linearity of CCD cameras. This method is more sensitive and accurate as well as more intuitive, especially in measuring around the 0.1%--0.2% range of nonlinearity. 2) To illustrate the advantage of the method, the linearity performance of the CCD cameras at CJLOA has been measured and analysed. 3) For the CCD systems tested, there is no unique formula to represent the correlation over the entire CCD frame between the deviation from linearity and the pixel value, i.e., different pixel has different correction even though their pixel values are the same. 4) For the BFOSC (BAO Faint Object Spectrograph Camera) Loral CCD camera and the Tek CCD camera at the 1.56-m reflector, blooming (bleeding) happens long before saturation, and we suspect whether it could have resulted from the charge transfer efficiency (CTE) not being high enough.

Key words:  instrumentation: detectors --- telescopes

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ChJAA, 2004, Vol.4, No.4

Chinese Journal of Astronomy and Astrophysics: Online Edition

http://www.chjaa.org 

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