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{\LARGE\bf Chinese Journal of Astronomy and Astrophysics}\\

2005, Vol.5, No.3 (June 20, 2005)



Extragalactic Astronomy Stars The Sun
Instruments, observational techniques and data processing


Relation between Starlight and Nebular Emission Lines of Star-Forming Galaxies

Hong-Lin Lu1, Hong-Yan Zhou2, Ting-Gui Wang2, Zhen-Quan Zhuang1, Xiao-Bo Dong2, Jun-Xian Wang2, and Cheng Li2

1 Department for Electronics of Science & technology, University of Science and Technology of China, Hefei 230026; mtzhou@ustc.edu.cn
2 Center for Astrophysics, University of Science and Technology of China, Hefei 230026

We present an exercise that intends to establish a relationship between the strength of nebular emission lines and optical stellar features in the spectrum of a galaxy. After accurately subtracting the stellar continuum and the underlying stellar absorption, we made reliable measurements of the emission lines of all the galaxies in the Sloan Digital Sky Survey Data Release 2 (SDSS DR2). More than 4000 star-forming galaxies with high S/N ratio of both the stellar spectrum and the emission lines are selected. These galaxy spectra are fitted with the 10 PCs of Yip et al., after all the emission line regions have been filtered out. We find that the flux of hydrogen Balmer emission lines, H$\alpha$ and H$\beta$ can be well recovered from the PCs, while the metal lines are not well reproduced. The fluxes of H$\alpha$ and H$\beta$ measured from the PC-reconstructed spectra and from the observed spectra agree well with an rms scatter of only $\sim
0.1$ dex. This result suggests that, with moderate spectral resolution and S/N ratio, the optical stellar spectrum of a galaxy can serve as an indicator of star formation rate.

Key words:   galaxies: fundamental parameters -- galaxies: starburst -- radiation: lines, continuum

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The Correlation between Gamma-ray and Radio Emissions in $\gamma$-ray Loud Blazars

Jiang-He Yang 1, 2 and Jun-Hui Fan^2, 3, 4

1 Department of Physics and Electronics Science, Hunan University of Arts and Science, Changde 415000; fjh@gzhu.edu.cn; yjianghe@163.com
2 Center for Astrophysics, Guangzhou University, Guangzhou 510405 3 National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 4 Physics Institute, Hunan Normal University, Changsha 410081

We collect 119 $\gamma$-ray-loud blazars (97 flat spectrum radio quasars (FSRQs) and 22 BL Lacertae objects (BL Lacs)), and investigate possible correlations between their $\gamma$-ray emission (maximum, minimum and average values) at 1GeV and the radio emission at 8.4GHz. Our main results are as follows. For the lower state $\gamma$-ray data, there is no correlation between the $\gamma$-ray and radio flux density; For the high state $\gamma$-ray data, there are good correlations for the whole 119 blazars and 97 FSRQs, and a weak correlation for the 22 BL Lac objects; For the average $\gamma$-ray data, there are good correlations. According to our analysis, we propose that the $\gamma$-rays are associated with the radio emission from the jet, and that the $\gamma$-ray emission is likely from the SSC process in this case.

Key words:   Galaxies: active -- BL Lacertae objects -- quasars

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A Differential Abundance Analysis of HD219175A and B

Hua-Wei Zhang 1 and Gang Zhao 2

1 Department of Astronomy, School of Physics, Peking University, Beijing 100871; zhw@bac.pku.edu.cn
2 National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012

The abundances of the wide binary pair HD219175 A and B are determined and compared using a line-by-line differential analysis. No evidence for difference has been found in the abundances of Fe, O, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Ni, Cu and Ba. Our results support a physical relation between the two components of HD219175.

Key words:   stars: abundances -- stars: atmospheres -- binaries: visual

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A Model of the Circumstellar Envelope of Luminous Blue Variables

Jian-Heng Guo 1,2, Yan Li1 and Hong-Guang Shan1

1 National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, Kunming 650011; guojh@ynao.ac.cn
2 Graduate School of Chinese Academy of Sciences, Beijing 100039

The continuum energy distributions of the luminous blue variables R127 and R110 in the outburst phase are fitted with a circumstellar envelope model. Both stars show two peaks in their continuum, one near 1250Å and the other in the optical band. We suggest that their UV and optical fluxes may have different origins: the UV flux comes from the central star while the optical flux comes from an expanding circumstellar envelope. We construct a model for LBVs consisting of two LTE atmosphere models with different temperatures, and find it to be in agreement with the observed spectral energy distributions of R127 and R110. According to our numerical experiments, R127's continuum is composed of fluxes from a circumstellar envelope of $T_{\rm eff}=8000$K, $R=485R_{\odot }$, and log g=1, and from a central star of $T_{\rm eff}=17\,000$K, $R=135R_{\odot }$, and log g=2.5 with a permeating factor f=0.5; while R110's continuum can be fitted by a circumstellar envelope of $T_{\rm eff}=7000$K, $R=350R_{\odot }$, and $\log g=0.5$, and a central star of $T_{\rm
eff}=25\,000$K, $R=27R_{\odot }$, and log g=3.0 with a permeating factor f=0.65. Both models show that the non-spherically symmetric, optically thick regions are formed surrounding the central star in the outburst phase. The light of the central star is shielded by the circumstellar envelope so that the visual brightness increases with the decrease/increase of the temperature/radius of the optically thick regions.

Key words:   stars: variables: LBVs -stars: continuum spectrum -stars: mass loss

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Variability Analysis of EGRET Gamma-Ray Sources

Zhao-Xia Han1 and Li Zhang1,2

1 Department of Physics, Yunnan University, Kunming 650091; hanzhaoxia@sohu.com
2 National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, Kunming 650011; astroynu@public.km.yn.cn

The variability of $\gamma$-ray sources listed in the third EGRET catalog is studied using three variability indices. These indices are found to be statistically equivalent if the observed data are sufficiently accurate. Using the three indices, 30 EGRET point sources which are positionally coincident with pulsars and 40 persistent unidentified sources at low latitudes are analyzed for their variability status. It is found that 14 of the 30 point sources may have genuine or plausible associations with pulsars, and 16 of the 40 persistent unidentified sources are possible pulsar candidates.

Key words:   gamma-rays: observations -- galaxies: statistics -- stars: variables

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Two Sympathetic Homologous CMEs on 2002 May 22

Jian-Xia Cheng, Cheng Fang, Peng-Fei Chen and Ming-De Ding

Department of Astronomy, Nanjing University, Nanjing 210093; chengjianxia@nju.org.cn

Sympathetic coronal mass ejections (CMEs) usually occur in different active regions connected by interconnecting magnetic loops, while homologous CMEs occur within the same active region with an almost the same background magnetic field, and so are similar in shapes. Two sympathetic CMEs erupted within 3 hours on 2002 May 22, originating from the same active region, AR 9948. Their multi-wavelength data were collected and analyzed. It is suggested that emerging flux triggered the occurrence of the first CME and the corresponding flare, the reconnection inflow of which in turn triggered the eruption of the second CME. Based on the fact that the two sympathetic CMEs have many similarities, in their shapes, their low-lying dimming areas, etc., we tentatively propose, for the first time, the phenomenon of sympathetic homologous CMEs.

Key words:   sun: filament -- sun: flares -- sun: CMEs

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Chromospheric Internetwork Oscillations at Various Locations of the Quiet Sun

Zong-Jun Ning1,2 and Ming-De Ding1

1 Department of Astronomy, Nanjing University, Nanjing 210093; ningzongjun@hotmail.com
2 Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008

We analyze oscillation behaviours in chromospheric internetwork regions using spectral observations of the CII1334Å line obtained with the Solar Ultraviolet Measurements of Emitted Radiation spectrograph (SUMER) aboard Solar and Heliospheric Observatory (SOHO). Three areas, 26 x 120 ${\rm {arcsec}}^2$ each, at the various latitudes from the disk center to the north polar coronal hole, were rastered with a cadence of about 40-60 s in the solar minimum year. We obtained the time evolution of two-dimensional (2D) line intensity, continuum and line core shift. The continuum and the line shift show $\sim$3 min chromospheric oscillations in the internetwork regions underlying the coronal hole as well as at the disk center. We find that the CII1334Å line shift oscillates with an average speed of $\sim$1.7  $\rm {km~s}^{-1}$, independent of the latitude, while its coherent scale decreases with latitude. On the other hand, the oscillation amplitude of the continuum around the 1334Å and the phase delay between the Doppler shift and continuum slightly increase with latitude.

Key words:   Sun: chromosphere -- Sun: oscillations

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Resonant Heating of Ions by Parallel Propagating Alfvén Waves in Solar Coronal Holes

Tian-Xi Zhang 1, 2, Jing-Xiu Wang1 and Chi-Jie Xiao 1

1 National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012; wangjx@bao.ac.cn
2 Center for Space Plasma and Aeronomic Research, The University of Alabama in Huntsville, Huntsville, AL 35899, USA; zhangt@cspar.uah.edu

Resonant heating of H, O+5, and Mg+9 by parallel propagating ion-cyclotron Alfvén waves in solar coronal holes at a heliocentric distance is studied using the heating rate derived from the quasilinear theory. It is shown that the particle-Alfvén-wave interaction is a significant microscopic process. The temperatures of the ions are rapidly increased up to the observed order in only microseconds, which implies that simply inserting the quasilinear heating rate into the fluid/MHD energy equation to calculate the radial dependence of ion temperatures may cause errors as the time scales do not match. Different species ions are heated by Alfvén waves with a power law spectrum in approximately a mass order. To heat O+5 over Mg+9 as measured by the Ultraviolet Coronagraph Spectrometer (UVCS) in the solar coronal hole at a region $\gs 1.9 R_{\odot}$, the energy density of Alfvén waves with a frequency close to the O+5-cyclotron frequency must be at least double of that at the Mg+9-cyclotron frequency. With an appropriate wave-energy spectrum, the heating of H, O+5 and Mg+9 can be consistent with the UVCS measurements in solar coronal holes at a heliocentric distance.

Key words:   acceleration of particles -- plasmas -- waves -- solar wind -- Sun: corona

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The Role of Nuclei-Nuclei Interactions in the Production of Gamma-ray Lines in Solar Flares

Boris M. Kuzhevskij 1,2 and Wei-Qun Gan1, and Leonty I. Miroshnichenko1,3

1 Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008; wqgan@pmo.ac.cn
2 Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, 119992, Moscow, Russia; bmk@srd.sinp.msu.ru
3 IZMIRAN, Troitsk, Moscow Rigion, 142190, Russia; leonty@izmiran.rssi.ru

Dramatic extensions of experimental possibilities (spacecraft RHESSI, CORONAS-F and others) in solar gamma-ray astronomy call for urgent, detailed theoretical consideration of a set of physical problems of solar activity and solar-terrestrial relationships that earlier may have only been outlined. Here we undertake a theoretical analysis of issues related to the production of gamma-radiation in the processes of interactions of energetic (accelerated) heavy and middle nuclei with the nuclei of the solar atmosphere (the so-called i-j interactions). We also make an estimate of the contribution of these interactions to the formation of nuclear and isotopic abundances of the solar atmosphere in the range of light and rare elements. The analysis is carried out for solar flares in the wide range of their intensities. We compare our theoretical estimates with RHESSI observations for the flare of 2002 July 23. It was shown that the 24Mg gamma-ray emission in this event was produced by the newly generated Mg nuclei. With a high probability, the gamma-ray line emission of 28Si nuclei from this flare was generated by the same processes.

Key words:    acceleration of particles -- nuclear reactions -- Sun: flares -- Sun: X-rays, gamma-rays

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Calculations for the Pre-Calibration of LAMOST Active Optics

Yong Zhang1, 2 and Xiang-Qun Cui 1

1 National Astronomical Observatories / Nanjing Institute of Astronomical Optics & Technology, Chinese Academy of Sciences, Nanjing 210042; yzh@niaot.ac.cn
2 Graduate School of the Chinese Academy of Sciences, Beijing 100039

Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) is one of the major on-going national large scientific projects in China. Active optics is a key technology for the LAMOST with which the thin-mirror active optics and segmented-mirror active optics are tied in. A pre-calibration method considering all active forces and displacements specially for LAMOST has been developed in early 2004. We give a detailed mathematical derivation and calculation including numerical simulation and computer program realization of the pre-calibration method of LAMOST open-loop control for the third-order aspherical aberration. We have also carried out calculations on the application of the pre-calibration method and the parameters of actuator design in LAMOST active optics in observation mode, including estimations of the actuator ranges, the interval of active optics correction and the ranges and trends of load changes on all the actuators during LAMOST tracking a given star.

Key words:active optics -- telescopes -- instrumentation

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Characteristics and Performance of the CCD Photometric System at Lulin Observatory

Daisuke Kinoshita1,2, Chin-Wei Chen1, Hung-Chin Lin 1, Zhong-Yi Lin 1, Kui-Yun Huang 1, Yung-Shin Chang 1, and Wen-Ping Chen 1

1 Institute of Astronomy, National Central University, 300 Jungda Rd, Jungli City, Taoyuan, 320-54, Taiwan; kinoshita@astro.ncu.edu.tw
2 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo, 181-8588, Japan

The Lulin One-meter Telescope at Lulin Observatory in Taiwan started open-use observations in January 2003. In order to evaluate the performance of the CCD photometric system, the characteristics and quality of the site, we obtained data of photometric standards as well as calibration data from February to November 2004. We report here the results of our analysis including the gain, readout noise, dark current and linearity of the CCD camera, and transformation coefficients, total throughputs, night sky brightnesses and limiting magnitudes for UBVRI bands.

Key words:   instrumentation: miscellaneous -- site testing -- telescopes

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ChJAA, 2005, Vol.5, No.3

Chinese Journal of Astronomy and Astrophysics: Online Edition


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Created by Aiying Zhou 2005-06-04