A New Method of Identifying 3D
Null Points in Solar Vector Magnetic Fields
Hui Zhao, Jing-Xiu Wang, Jun Zhang and Chi-Jie Xiao
National Astronomical Observatories, Chinese Academy of Sciences,
Beijing 100012 zhaohui@ourstar.bao.ac.cn
Abstract
Employing the Poincaré index of isolated
null-points in a vector field, we worked out a mathematical method
of searching for 3D null-points in coronal magnetic fields. After
introducing the relevant differential topology, we test the method
by using the analytical model of Brown & Priest. The location of
null-point identified by our method coincides precisely with the
analytical solution. Finally we apply the method to the 3D coronal
magnetic fields reconstructed from an observed MDI magnetogram of
a super-active region (NOAA 10488). We find that the 3D null-point
seems to be a key element in the magnetic topology associated with
flare occurrence.
Key Words: Sun: flares -- Sun: corona -- Sun:
magnetic fields
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Radio Identifications of Markarian
Galaxies and the Correlation between
Radio and Far-Infrared Properties
Shao-Guang Luo1,2 - Xue-Bing Wu1
1 Department of Astronomy, Peking University, Beijing
100871; luo@vega.bac.pku.edu.cn
2 Shenzhen Graduate School, Peking University, Shenzhen
518055
Abstract
By checking DSS
optical images and NVSS radio images,
782 Markarian galaxies were identified to be NVSS radio sources.
A comparison of the radio luminosity at 1.4GHz and the
far-infrared (FIR) luminosity for 468 ``normal" galaxies shows a
tight correlation. Most of the Seyfert galaxies and quasars follow
the radio-FIR relation deduced from the ``normal" galaxy sample,
but with a somewhat larger scatter. A total 167 Markarian
galaxies, comprising 100 ``normal" galaxies, 66 Seyfert galaxies
and one quasar, have either excess radio emission or much lower
FIR spectral index

. These
galaxies may be classified as ``AGN-powered". For ``normal"
galaxies, the average
q value (defined as the log ratio between
FIR and radio luminosities) is 2.3. There seems a trend for
q
to
slightly decrease with increasing radio luminosity. This may imply
that the ongoing active star formation in galaxies with higher
radio luminosities is more efficient in

the
cosmic-ray electrons.
Key Words: galaxies: active -
galaxies: Seyfert - galaxies: starburst - radio
continuum: galaxies - infrared: galaxies
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Separation of Different
Contributions to the Total X-ray
Luminosity in Gamma-ray Loud Blazars
Jun-Hui Fan1, 2, Gustavo E. Romero3,
Yong-Xiang Wang4 and Jiang-Shui Zhang1
1 Center for Astrophysics, Guangzhou University, Guangzhou
510400; fjh@gzhu.edu.cn
2 National Astronomical Observatories, Chinese Academy of
Sciences, Beijing 100012
3 Instituto Argentino de Radioastronomía, C.C.5,
(1894) Villa
Elisa, Bs. As., Argentina
4 College of Science and Trade, Guangzhou University,
Guangzhou 511442
Abstract
The relativistic beaming model has been successfully
used to explain many of the observational properties of active
galactic nuclei. In this model the total emission is formed by two
components, one beamed, one unbeamed. However, the exact
contribution from each component in unresolved sources is still
not clear. In the radio band, the core and extended emissions are
clearly separated. We adopt the method proposed by Kembhavi to
separate the two contributions in the X-ray emissions in a sample
of 19 gamma-ray loud blazars. It is clearly shown that the beamed
emission dominates the X-ray flux and the unbeamed X-ray emission
is correlated with the extended radio emission of the considered
objects. We also find that the ratio of the beamed to the unbeamed
X-ray luminosity is correlated with the X-ray spectral index, an
effect that should be a consequence of the underlying X-ray
emission mechanism.
Key Words: galaxies: active-galaxies -- jets --
X-rays: galaxies
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Estimates of AGN Black Hole Mass
and Minimum Variability Timescale
Guang-Zhong Xie1,2, Luo-En Chen1,4,5,
Huai-Zhen Li1,5, Li-Sheng Mao1,5, Hong Dai1,2,5,
Zhao-Hua Xie3, Li Ma1,3,5 and Shu-Bai Zhou1
1 National Astronomical Observatories, Yunnan
Observatory, Chinese Academy of Science, Kunming 650011;
gzxie@public.km.yn.cn
2 Yunnan Astrophysics Center, Yunnan University,
Kunming 650091
3 Physics Department, Yunnan Normal University, Kunming
650091
4 Physics Department, Yuxi Normal College, Yuxi 653100
5 Graduate University of Chinese Academy of Sciences,
Beijing
100049
Abstract
Black hole mass is one of the
fundamental physical
parameters of active galactic nuclei (AGNs), for which many
methods of estimation have been proposed. One set of methods
assumes that the broad-line region (BLR) is gravitationally bound
by the central black hole potential, so the black hole mass can be
estimated from the orbital radius and the Doppler velocity.
Another set of methods assumes the observed variability timescale
is determined by the orbital timescale near the innermost stable
orbit around the Schwarzschild black hole or the Kerr black hole,
or by the characteristic timescale of the accretion disk. We
collect a sample of 21 AGNs, for which the minimum variability
timescales have been obtained and their black hole masses
(

) have been well estimated from the
stellar
velocity dispersion or the BLR size-luminosity relation. Using the
minimum variability timescales we estimated the black hole masses
for 21 objects by the three different methods, the results are
denoted by
Ms,
Mk and
Md,
respectively. We compared each of them with

individually and found that: (1) using the minimum variability
timescale with the Kerr black hole theory leads to small
differences between

and
Mk,
none
exceeding one order of magnitude, and the mean difference between
them is about 0.53 dex; (2) using the minimum variability
timescale with the Schwarzschild black hole theory leads to
somewhat larger difference between

and
Ms: larger than one
order of magnitude for 6 of the 21
sources, and the mean difference is 0.74 dex; (3) using the
minimum variability timescale with the accretion disk theory leads
to much larger differences between

and
Md, for 13 of the 21 sources the differences are larger
than two orders of magnitude;
and the mean difference is as high as about 2.01 dex.
Key Words: galaxies: active -- galaxies: nuclei --
galaxies:
fundamental parameters
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Statistical Properties of a
Blazar Sample and Comparison of HBLs, LBLs and FSRQs
Li-Sheng Mao1, 2, Guang-Zhong Xie1,3, Jin-Ming
Bai1, and Hong-Tao Liu1,2
1 Yunnan Observatory, National Astronomical Observatories,
Chinese Academy of Sciences, Kunming 650011; maolisheng1981@126.com
2 Graduate University of Chinese Academy of Sciences,
Beijing 100049
3 Yunnan Astrophysics Center, Yunnan University, Kunming,
650091
Abstract
Making use of the 2MASS Data Release, we have searched
for near-infrared (JHK) counterparts to 268 blazars from Donato et
al. and obtained 238 counterparts within 5'' in the area covered
by 2MASS. It provides us a sample with infrared data several times
larger than the previous one of the same kind. Based on our sample
and the sample by Donato et al., we have compared in detail the
properties of HBLs, LBLs and FSRQs from five aspects and found
that HBLs are significantly different from LBLs and FSRQs while
LBLs are not obviously different from FSRQs. Our results strongly
support the division of BL Lac objects into the high-frequency
peaked (HBL) and low-frequency peaked (LBL) objects introduced by
Padovani & Giommi and show that HBLs and LBLs are two kinds of
blazar having different physical properties.
Key Words: BL Lacertae
objects: general-- infrared: galaxies -- methods: statistical
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Fallback Disk-Involved Spin-Down
of Young Radio Pulsars
Zi-Bo Jiang and Xiang-Dong Li
Department of Astronomy, Nanjing University, Nanjing 210093; lixd@nju.edu.cn
Abstract
Disks originating from supernova fallback have been
suggested to surround young neutron stars. Interaction between
the disk and the magnetic field of the neutron star may considerably
influence the evolution of the star through the so called propeller
effect. There are many controversies about the efficiency of the
propeller mechanism proposed in the literature. We investigate the
fallback disk-involved spin-down of young pulsars. By comparing the
simulated and measured results of pulsar evolution, we present some
possible constraints on the propeller torques exerted by the disks on
neutron stars.
Key Words: stars: magnetic fields -- stars: neutron
-- pulsars: individual: PSRs B0532+21, B0833+45, B0540-69, B1509-58
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Autoregressive Spectral Estimation for
Quasi-Periodic Oscillations
Li Chen1 and Ti-Pei Li2,3
1 Department of Astronomy, Beijing Normal University,
Beijing 100875; chenli@bnu.edu.cn
2 Center for Astrophysics, Tsinghua University, Beijing
100084
Key Lab. of Particle Astrophysics, Inst. of High Energy Physics,
Chinese Academy of Sciences, Beijing 100039
Abstract
Modern methods of spectral estimation based on
parametric time-series models are useful tools in power spectral
analysis. We apply the autoregressive (AR) model to study
quasi-periodic oscillations (QPOs). An empirical formula to
estimate the expectation and standard deviation of the noise AR
power densities is derived, which can be used to estimate the
statistical significance of an apparent QPO peak in an AR
spectrum. An iterative adding-noise algorithm in AR spectral
analysis is proposed and applied to studying QPOs in the X-ray
binary Cir X-1.
Key words: methods: data analysis -- stars:
individual (Circinus X-1) -- X-rays: stars
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Observational Characteristics of
Radio Emission Related to
Multi-polar Magnetic Configuration
Min Wang1, Rui-Xiang Xie1, Chun Xu1,
Shuo-Biao Shi1 and Yi-Hua Yan2
1 National Astronomical Observatories, Yunnan Observatory,
Chinese Academy of Sciences, Kunming 650011; wm@ynao.ac.cn
2 National Astronomical Observatories, Chinese Academy of
Sciences, Beijing 100012
Abstract
We present a large complex radio burst and its
associated fast time structures observed on 2001 April 10 in the
frequency range of 0.65-7.6GHz. The NoRH radio image
observation shows very complex radio source structures which
include preexisting, newly emerging, submerging/cancelling
polarities and a bipolar, a tripolar (a `bipolar + remote
unipolar'), and a quadrupolar structure. This suggests that the
radio burst is generated from a very complicated loop structure.
According to the spectral and image observations, we assume that
the beginning of this flare was caused by a single bipolar loop
configuration with a `Y-type' reconnection structure. A composite
of radio continuum and fast time structures is contained in this
flare. The various fast radio emission phenomena include normal
and reverse drifting type III bursts, and slowly drifting and
no-drift structures. The tripolar configurations may form a
double-loop with a `three-legged' structure, which is an important
source of the various types of fast time structures. The two-loop
reconnection model can lead simultaneously to electron
acceleration and corona heating. We have also analyzed the
behaviors of coronal magnetic polarities and the emission
processes of different types radio emission qualitatively.
Interactions of a bipolar or multi-polar loop are consistent with
our observational results. Our observations favor the magnetic
reconnection configurations of the `inverted Y-type' (bipolar) and
the `three-legged' structures (tripolar or quadrupolar).
Key Words: Sun: radio radiation -- Sun: activity --
Sun: flares
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Multi-wavelength Diagnostics of
Bombardment
by Non-thermal Particles in Solar Flares
Zhi Xu1, Cheng Fang1, and Wei-Qun Gan2
1 Astronomy Department of Nanjing University, Nanjing
210093; xuzhi@nju.edu.cn
2 Purple Mountain Observatory, Chinese Academy of
Sciences, Nanjing 210008
Abstract
Chromospheric lines, including H

, Ly

, Ly

and CaII K, CaII 8542, are systemically and quantitatively
investigated with respect to the non-thermal excitation and
ionization due to particle beam bombardment for a series of solar
semi-empirical atmospheric models. As a result we propose to use
the contrast in the integrated intensity of hydrogen lines to
estimate the total energy flux of the bombarding beam during the
solar flare impulsive phase. Partial frequency redistribution is
considered in the Ly

line calculation and
a smaller
intensity enhancement in the H

line-centers is
found than
in the previous results of Fang et al.
Key Words: Sun: flare -- Sun: chromosphere
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Polar Coronal Holes During Solar
Cycles 22 and 23
Jun Zhang1,2, J. Woch2, S. Solanki2
1 National Astronomical Observatories, Chinese Academy of
Sciences, Beijing 100012 zjun@ourstar.bao.ac.cn
2 Max-Planck-Institut für Sonnensystemforschung,
Katlenburg-Lindau, D-37191, Germany
Abstract
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.
Key Words: Sun: coronal -- Sun: particle emission --
Sun: solar wind
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Estimating the Size and Timing
of the Maximum Amplitude of Solar Cycle 24
Ke-Jun Li1, Peng-Xin Gao1,2 and Tong-Wei Su1,2
1 National Astronomical Observatories, Yunnan Observatory,
Chinese Academy of Sciences, Kunming 650011; lkj@ynao.ac.cn
2 Graduate University of Chinese Academy of Sciences,
Beijing 100049
Abstract
A simple statistical method is used to estimate the size
and timing of maximum amplitude of the next solar cycle (cycle
24). Presuming cycle 23 to be a short cycle (as is more likely),
the minimum of cycle 24 should occur about December 2006 (

months) and the maximum, around March 2011 (

months), and
the amplitude is

, if it is a fast
riser, or about
136, if it is a slow riser. If we presume cycle 23 to be a long cycle
(as is less likely), the minimum of cycle 24 should
occur about June 2008 (

months) and the
maximum, about
February 2013 (

months) and the maximum will be
about 137
or 80, according as the cycle is a fast riser or a slow riser.
Key Words: Sun: activity -- Sun: sunspot -- Sun:
prediction
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A Study on the Paul-Baker System
as an Instrument for Multi-object Spectrum Observation
Xiang-Yan Yuan1, Ding-Qiang Su1, 2, Xiang-Qun
Cui1 and Gen-Rong Liu1
1 National Astronomical Observatories, Nanjing Institute
of Astronomical Optics & Technology, Chinese Academy of Sciences,
Nanjing 210042; xyyuan@niaot.ac.cn
2 Department
of Astronomy, Nanjing University, Nanjing 210093
Abstract
Paul-Baker systems with 4 flat field and 5 flat
field are studied. Their light obstructions under different
f/ratios of the primary mirror are analyzed. Due to the strong
f/ratio of the system, a focal length extender is designed in
order to match the following fiber instrumentation, and two kinds
of dispersion prism correctors are designed for correcting the
atmospheric dispersion. We compare the designed Paul-Baker system
with LAMOST, the national major scientific project now under
construction.
Key Words: techniques: telescopes --
instrumentation: miscellaneous
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The OH Maser Line Receiving
System for the Urumqi 25m Radio Telescope
Hong-Bo Zhang1, Jarken Esimbek2, Jian-Jun Zhou1,
2, Xing-Wu Zhen3, Xi-Zhen Zhang1 and
Wen-Jie Yang4
1 National Astronomical Observatories, Chinese Academy of
Sciences, Beijing 100012 zhanghb@bao.ac.cn
2 Urumqi Astronomical Observatory, National Astronomical
Observatories, Chinese Academy of Sciences, Urumqi 830011
3 Department of Astronomy, Nanjing University 210093
4 Beijing Institute of Tracking and Telecommunication
Technology, Beijing 100094
Abstract
A maser spectral line system is newly implemented on the Urumqi
25m Radio Telescope. The system consists mainly of a cooling
receiver and a 4096 channels digital correlation spectrometer. The
frequency resolution of the spectrometer at the maximum signal
bandwidth of 80MHz is 19.5kHz. After careful calibrations observation
at the 1665MHz OH maser emission was made towards a number of sources,
including W49N and W75N. The observed results demonstrate that the
digital correlation spectrometer is suitable for astronomical spectral
line observations.
Key Words: instrumentation: spectrometer -- OH maser
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ChJAA, 2005,
Vol.5, No.5
Chinese Journal of
Astronomy and Astrophysics: Online
Edition
http://www.chjaa.org
Copyright 2001--2008 All rights reserved. The National
Astronomical
Observatories of
Chinese Academy of Sciences, P.R. China. This Journal or parts thereof,
may not be
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This page was created on 2005-10-08