$\textstyle \parbox{150mm}{ {\LARGE\bf Chinese Journal of Astronomy and Astrophysics}\\ }$

2008, Vol.8, No.3 (June 20, 2008)

Contents

RESEARCH PAPERS

Extragalactic Astronomy

 Stars
Astrophysical Processes
The Sun
Instruments, Observational Techniques and Data Processing




Abstract

The Structure of Narrow-Line Region in LINERs

Hai-Feng Dai and Ting-Gui Wang

1 Center for Astrophysics, University of Science and Technology of China, Hefei 230026, China; twang@ustc.edu.cn, daihf@mail.ustc.edu.cn
2 Joint Instotute of Galaxies and Cosmology, Shanghai Observatory and USTC, China

Abstract
Low-ionization nuclear emission regions (LINERs) are present in a large fraction of local galaxies, while their connection to the more luminous active galactic nuclei (AGN) remains elusive. We analyze the narrow band images obtained by the Hubble Space Telescope (HST) in H$\alpha$+[NII] and/or [OIII] band for 23 LINERs and low luminosity Seyfert galaxies in the sample of the Palomar Optical Spectroscopic Survey of nearby galaxies in an attempt to resolve the structure of Narrow Emission Line Regions (NLRs) of these objects. In all cases, NLRs are well resolved and their morphology differs from object to object. Clumps, linear structure, spiral arms or a ring are detected in a large fraction of the objects, while there is no significant difference between Seyfert galaxies and LINERs. We find that the NLR size and the narrow line luminosity are strongly correlated for both LINERs and low luminosity Seyfert galaxies, and that the size of H$\alpha$+[NII] emission line region scales with H$\alpha$ luminosity as $R_{\rm NLR}\propto L_{{\rm H}\alpha}^{0.44\pm 0.06}$, consistent with an extension of the NLR size-luminosity relation defined for luminous Seyfert galaxies and quasars, to two orders of magnitude lower in luminosity and to lower activity levels. Our results suggest that NLRs in LINERs are similar to those of Seyfert galaxies, and they are powered by the central active galactic nucleus.

Key Words:   galaxies: active -- galaxies: Seyfert -- galaxies: structure -- LINER


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Does the Amati Relation depend on the Luminosity of the GRB's Host Galaxy?

Jing Wang, Jing-Song Deng and Yu-Lei Qiu

National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China; wj@bao.ac.cn

Abstract
In order to test the systematics of the Amati relation, 24 long-duration GRBs with available $E_{\gamma,\mathrm{iso}}$ and Ep are separated into two subgroups according to the B-band luminosity of their host galaxies. The Amati relations in the two subgroups are found to be in agreement with each other within the uncertainties. Taking into account of the well established luminosity - metallicity relation of galaxies, no strong evolution of the Amati relation with the GRB's environmental metallicity is implied in this study.

Key Words:   gamma-rays: bursts -- gamma-rays: observations -- galaxies: evolution


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Effects of $\alpha$-Enhancement on Stellar Evolution

Jian-Po Guo 1,2, Feng-Hui Zhang 1, Xue-Fei Chen 1 and Zhan-Wen Han 1

1 National Astronomical Observatories / Yunnan Observatory, Chinese Academy of Sciences, Kunming 650011, China; guojianpo1982@hotmail.com

2 Graduate School of Chinese Academy of Sciences, Beijing 100049, China

Abstract
Using Eggleton's code, we systematically show the differences in stellar evolution between the results based on the scaled-solar mixture and the metal mixture. As input, the OPAL high temperature opacities are used for $\log (T/{\rm K})>4.00$, and the new Wichita State low temperature opacities, for $\mathrm{log(}\mathit{T}\mathrm{/K)}\leq 4.00$. Our calculations cover star masses ranging from 0.25 to 80.0, spaced at $\Delta\log M =0.10$ or 0.05. The values of metallicities Z are 0.0001, 0.0003, 0.001, 0.004, 0.01, 0.02, 0.03, 0.04, 0.06, 0.08 and 0.10. For a given Z, the initial hydrogen mass fraction is given by X=0.76-3.0Z. We show that can raise the stellar effective temperature and luminosity, and reduce the evolutionary age. Compared with some previous work, the effects of are more obviously demonstrated in our calculations.

Key Words:   abundances -- stars: evolution -- stars: general


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Microscopic Magnetic Dipole Radiation in Neutron Stars

Hao Tong, Qiu-He Peng and Hua Bai

Department of Astronomy, Nanjing University, Nanjing 210093, China; htong_2005@163.com

Abstract
There is a 3P2 neutron superfluid region in NS (neutron star) interior. For a rotating NS the 3P2 superfluid region is like a system of rotating magnetic dipoles. It will give out electromagnetic radiation, which may provide a new heating mechanism of NSs. This mechanism plus some cooling agent may give a sound explanation to NS glitches.

Key Words:   stars: neutron -- pulsars: general -- dense matter -- magnetic fields


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Observations of Giant Pulses of the Crab Pulsar

Ling-Jun Kong 1,2, Ali Esamdin 1, Cheng-Shi Zhao 1,2, Zhi-Yong Liu 1 and Jian-Ping Yuan 1,2

1 Urumqi Observatory, NAOC, Chinese Academy of Sciences, Urumqi 830011, China; aliyi@uao.ac.cn

2 Graduate University of Chinese Academy of Sciences, Beijing 100049, China

Abstract
The Crab Pulsar was observed at 1540MHz with the 25m radio telescope at Urumqi with a filterbank de-dispersion backend. A total of 2436 giant pulses with pulse energies larger than 4300Jy $\mu$s were detected in two observing sets. All of these giant pulses are located in the main pulse (MP) and inter pulse (IP) windows of the average profile of the Crab Pulsar. The ratio of the numbers of giant pulses detected in the IP and MP windows is about 0.05. Our results show that, at 1540MHz, the emission in the IP is contributed by giant and normal pulses, while that in the MP is almost dominated by giant pulses. The distribution of energy of the 2436 giant pulses at 1540MHz can be described by a power-law with index $\alpha$ = 3.13 $\pm$ 0.09. The intrinsic threshold of giant pulse energy in the MP window is about 1400Jy $\mu$s at 1540MHz.

Key Words:   stars: neutron -- pulsars: general -- pulsars: individual Crab Pulsar


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Third Order Effect of Rotation on Stellar Oscillations of a B Star

K. Karami 1,2,3

1 Department of Physics, University of Kurdistan, Pasdaran St., P. O. Box 66177-15175, Sanandaj, Iran Karami@iasbs.ac.ir

2 Research Institute for Astronomy & Astrophysics of Maragha (RIAAM), P. O. Box 55134-441, Maragha, Iran

3 Institute for Advanced Studies in Basic Sciences (IASBS), Gava Zang, P. O. Box 4519

Abstract
We aim at investigating the effect of rotation up to the third order in the angular velocity of a star on the p and g modes, based on the formalism developed by Soufi et al. Our ultimate goal is the study of oscillations of $\beta$ Cephei stars which are often rapidly rotating stars. Our results show that the third-order perturbation formalism presented by Soufi et al. should be corrected for some missing terms and some misprints in the equations. As a first step in our study of $\beta$ Cephei stars, we quantify by numerical calculations the effect of rotation on the oscillation frequencies of a uniformly rotating zero-age main-sequence star with 12 $M_\odot$. For an equatorial velocity of 100  $\rm km\,s^{-1}$, it is found that the second- and third-order corrections for (l,m)=(2,2), for instance, are of the order of 0.01$\%$ of the frequency for radial order n=6 and reaches up to 0.5$\%$ for n=14.

Key Words:   stars: $\beta$ Cephei variables -- stars: oscillation -- stars: rotation


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Swift/BAT Observations of X-Ray Flashes

Yi-Qing Lin

Department of Mathematics and Physics, Xiamen University of Technology, Xiamen 361024, China yqlin@xmut.edu.cn

Abstract
An analysis of prompt gamma-rays of X-ray flashes (XRFs) observed with the Swift/BAT has been presented. Our sample includes 235 bursts. It is found that the BAT detection ratio of XRFs to typical Gamma-ray bursts (GRBs) is 42:193, for division at $\Gamma=2$ (roughly corresponding $E_{\rm p}\sim 50$keV), $\Gamma$ being the power law index of the BAT spectrum and $E_{\rm p}$, the peak energy ($E_{\rm p}$) of the $\nu f_\nu$ spectrum. This is consistent with the HETE-2 observations. For both XRFs and GRBs $\Gamma$ are almost normally distributed in the range of 1 to 2.8, similar that observed with HETE-2. The distribution of $\Gamma$ for the entire set of GRBs/XRFs is not available due to poor statistics on the peak at $\Gamma>2.3$. This result probably indicates that the BAT spectrum of a typical XRF could have a $\Gamma$ of roughly 2.3, if they indeed are a distinct soft component of the GRB population. By comparing the fluence and the peak flux in different energy bands, it is found that the XRFs are ordinarily softer than the GRBs, but during the peak time the spectra of both GRBs and XRF are similar, showing that the dominant radiation mechanisms of both GRBs and XRFs are similar.

Key Words:   gamma-rays: bursts


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Detecting Very-High-Frequency Relic Gravitational Waves by a Waveguide

Ming-Lei Tong and Yang Zhang

Centre for Astrophysics, University of Science and Technology of China, Hefei 230026, China yzh@ustc.edu.cn

Abstract
The polarization vector (PV) of an electromagnetic wave (EW) will experience a rotation in a region of spacetime perturbed by gravitational waves (GWs). Based on this consideration, Cruise's group has built an annular waveguide to detect GWs. We give detailed calculations of the rotations of polarization vector of an EW caused by incident GWs from various directions and in various polarization states, and then analyze the accumulative effects on the polarization vector when the EW passes n cycles along the annular waveguide. We reexamine the feasibility and limitation of this method to detect GWs of high frequency around 100MHz, in particular the relic gravitational waves (RGWs). By comparing the spectrum of RGWs in the accelerating universe with the detector sensitivity of the current waveguide, it is found that the amplitude of the RGWs is too low to be detected by the waveguide detectors currently operating. Possible ways of improvements on detection are suggested.

Key Words:   early universe -- instrumentation: detectors -- gravitational waves --polarization


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Formation of Transient Coronal Holes during the Eruption of a Quiescent Filament and its Overlying Sigmoid

Li-Heng Yang 1,2, Yun-Chun Jiang 1 and Dong-Bai Ren 1,2

1 National Astronomical Observatories / Yunnan Observatory, Chinese Academy of Sciences, Kunming 650011, China; yangliheng@ynao.ac.cn

2 Graduate School of Chinese Academy of Sciences, Beijing 100049, China

Abstract
By using H$\alpha$, He I 10830, EUV and soft X-ray (SXR) data, we examined a filament eruption that occurred on a quiet-sun region near the center of the solar disk on 2006 January 12, which disturbed a sigmoid overlying the filament channel observed by the $\emph{GOES-12}$ SXR Imager (SXI), and led to the eruption of the sigmoid. The event was associated with a partial halo coronal mass ejection (CME) observed by the Large Angle and Spectrometric Coronagraphs (LASCO) on board the Solar and Heliospheric Observatory ($\emph{SOHO}$), and resulted in the formation of two flare-like ribbons, post-eruption coronal loops, and two transient coronal holes (TCHs), but there were no significantly recorded $\emph{GOES}$ or H$\alpha$ flares corresponding to the eruption. The two TCHs were dominated by opposite magnetic polarities and were located on the two ends of the eruptive sigmoid. They showed similar locations and shapes in He I 10830, EUV and SXR observations. During the early eruption phase, brightenings first appeared on the locations of the two subsequent TCHs, which could be clearly identified on He I 10830, EUV and SXR images. This eruption could be explained by the magnetic flux rope model, and the two TCHs were likely to be the feet of the flux rope.

Key Words:   Sun: filaments -- Sun: chromosphere -- Sun: coronal mass ejections (CMEs)


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Long-Term Sunspot Number Prediction based on EMD Analysis and AR Model

Tong Xu 1, Jian Wu 2, Zhen-Sen Wu 1 and Qiang Li 3

1 School of Science, Xidian University, Xi'an 710071, China; xutong1104@126.com

2 National Key Laboratory of Electromagnetic Environment, China Research Institute of Radio Wave Propagation, Beijing 102206, China

3 IAP, University of Rostock, Schlosstr. 6, Kuehlungsborn, 18225, Germany

Abstract
The Empirical Mode Decomposition (EMD) and Auto-Regressive model (AR) are applied to a long-term prediction of sunspot numbers. With the sample data of sunspot numbers from 1848 to 1992, the method is evaluated by examining the measured data of the solar cycle 23 with the prediction: different time scale components are obtained by the EMD method and multi-step predicted values are combined to reconstruct the sunspot number time series. The result is remarkably good in comparison to the predictions made by the solar dynamo and precursor approaches for cycle 23. Sunspot numbers of the coming solar cycle 24 are obtained with the data from 1848 to 2007, the maximum amplitude of the next solar cycle is predicted to be about 112 in 2011-2012.

Key Words:   Sun: sunspots -- Sun: activity


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Improving the Angular Resolution of Coded-Mask Telescopes by Direct Demodulation

Zong-Jun Shen and Jian-Feng Zhou

Department of Engineering Physics and Center for Astrophysics, Tsinghua University, Beijing 100084, China; shenzj98@mails.tsinghua.edu.cn

Abstract
We develop a new procedure to improve the angular resolution of coded-mask telescopes by the Direct Demodulation Method (DDM). DDM has been applied to both real and simulated data of INTEGRAL/IBIS. The angular resolution of IBIS/ISGRI has been improved from about 13' to 2'.

Key Words:   instrumentation: coded-mask -- telescopes: INTEGRAL/IBIS -- techniques: high angular resolution -- methods: direct demodulation


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Optical Design of Multilayer Achromatic Waveplate by Simulated Annealing Algorithm

Jun Ma 1, Jing-Shan Wang 2,4, Carsten Denker 3 and Hai-Min Wang 1,2

1 Big Bear Solar Observatory 40386 North Shore Lane, Big Bear City, CA 92314, USA jxm1901@njit.edu

2 New Jersey Institute of Technology, Center for Solar-Terrestrial Research, 323 Martin Luther Kind Blvd., Newark, NJ 07102, USA

3 Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany

4 Currently working at Thorlabs, Inc., 435 Route 206, Newton, NJ 07860, USA

Abstract
We applied a Monte Carlo method -- simulated annealing algorithm -- to carry out the design of multilayer achromatic waveplate. We present solutions for three-, six- and ten-layer achromatic waveplates. The optimized retardance settings are found to be $ 89\arcdeg51\arcmin39\arcsec \pm 0\arcdeg33\arcmin37\arcsec$ and $ 89\arcdeg54\arcmin46\arcsec \pm 0\arcdeg22\arcmin 4\arcsec $ for the six- and ten-layer waveplates, respectively, for a wavelength range from 1000 nm to 1800 nm. The polarimetric properties of multilayer waveplates are investigated based on several numerical experiments. In contrast to previously proposed three-layer achromatic waveplate, the fast axes of the new six- and ten-layer achromatic waveplate remain at fixed angles, independent of the wavelength. Two applications of multilayer achromatic waveplate are discussed, the general-purpose phase shifter and the birefringent filter in the Infrared Imaging Magnetograph (IRIM) system of the Big Bear Solar Observatory (BBSO). We also checked an experimental method to measure the retardance of waveplates.

Key Words:   instrumentation: spectrographs -- methods: numerical -- methods: laboratory -- Sun: infrared


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A Reinvestigation of the Physical Properties of Pismis 3 based on 2MASS Photometry

Tadross A. L.

National Research Institute of Astronomy and Geophysics, 11421 - Helwan, Cairo, Egypt altadross@nriag.sci.eg

Abstract
As a continuation of a series of work, we aim to refine and re-determine the physical parameters of previously rarely or un-studied open star clusters with good quality CMDs using Near-IR JHK photometry. Here we present a morphological analysis of the 2MASS database (the digital ``Two Micron All Sky Survey") for the open cluster Pismis 3. Some of the physical parameters are estimated for the first time, and some others, re-determined.

Key Words:   techniques: photometric -- Galaxy: open clusters and associations -- stars: luminosity function -- stellar clusters: individual: Pismis 3


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ChJAA, 2008, Vol.8, No.3

Chinese Journal of Astronomy and Astrophysics: Online Edition

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