2002, Vol.2, No.6 (December 20, 2002)


Contents

Letters
  • Searching for Variable Stars in and around Open Clusters   p.481
    Yu Xin, Xiao-Bin Zhang and Li-Cai Deng 
    Abstract | | PDF file (180 KB) | PS file *.gz  (331 KB) 
Extragalactic astronomy
  • Inclination of Broad Line Region in Narrow Line and Broad Line Seyfert 1 Galaxies    p.487
    Tian-Zhi Zhang and Xue-Bing Wu 
    Abstract | | PDF file (236 KB) | PS file *.gz  (262 KB) 
  • Properties of Broad Band Continuum of Narrow Line Seyfert 1 Galaxies    p. 501
    Hong-Yan Zhou and Ting-Gui Wang
    Abstract | | PDF file (538 KB) | PS file *.gz  (1001 KB) | Table 1: PDF PS 
Stars
  • Dynamical Evolution of Gamma-Ray Burst Remnants with Evolving Radiative Efficiency    p.525
    Jin-Bo Feng, Yong-Feng Huang,Zi-Gao Dai and Tan Lu 
    Abstract | | PDF file (178 KB) | PS file *.gz  (195 KB)  
  • How Fast Could a Proto-pulsar Rotate?    p.533
    Ren-Xin Xu, Hong-Guang Wang and Guo-Jun Qiao  
    Abstract | | PDF file (168 KB) | PS file *.gz  ( 91 KB) 
The Sun
  • Energetics and Propagation of Coronal Mass Ejections in Different Plasma Environments    p.539
    Jun Lin   
    Abstract | | PDF file (301 KB) | PS file *.gz  (648 KB) 
  • The Prediction of Maximum Amplitudes of Solar Cycles and the Maximum Amplitude of Solar Cycle 24    p.557
    Jia-Long Wang, Jian-Cun Gong,Si-Qing Liu,Gui-Ming Le and Jing-Lan Sun
    Abstract | | PDF file (146 KB) | PS file *.gz  (123 KB) 
Instruments, observational techniques and data processing
  • Inhomogeneity in Spectral Transmission of the Coated UBVRI Filters of BFOSC and its Influence on Photometry     p.563
    Bao-An Yao and Lin Huang   
    Abstract | | PDF file (329 KB) | PS file *.gz  (3117 KB) 


Abstract

Searching for Variable Stars in and around Open Clusters

Yu Xin, Xiao-Bin Zhang and Li-Cai Deng 


Affiliation: National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China

E-mail:  xinyu@ns3.bao.ac.cn   (corresponding author)

Abstract

We present a snapshot of our recent results of a variable star survey in 1 degree fields around three open clusters: NGC 188, NGC 7789 and M67. A total number of 39 variable stars are newly discovered, including 22 W UMa stars, 10 EA (Algol) type binaries, one RR-Lyr and one RRd pulsator, and five unclassified variables.

Key words: open clusters: individual: NGC 188, NGC 7789 and M67 --- stars: variables

PDF file (180 KB) | gzipped PS file (111 KB) | Back to Contents



Inclination of Broad Line Region in Narrow Line and Broad Line Seyfert 1 Galaxies   

Tian-Zhi Zhang and Xue-Bing Wu (*)

Affiliation:  Department of Astronomy, School of Physics, Peking University, Beijing 100871

E-mail:  wuxb@bac.pku.edu.cn     (corresponding author)

Abstract

The sizes of the Broad Line Region (BLR) of some Seyfert 1 galaxies and nearby quasars can be determined by the reverberation mapping method. Combining with the observed FWHM of H emission line and assuming that the motion of BLR clouds is virialized, the black hole masses of these objects have been estimated. However, this method strongly depends on the poorly-understood geometry and inclination of the BLR. On the other hand, a tight correlation between the black hole mass and the bulge velocity dispersion was recently found for both active and nearby inactive galaxies. This may provide another method, independent of the BLR geometry, for estimating the black hole mass. Using this method for estimating the black hole mass and combining with the measured BLR size and FWHM of H emission line, we derived the BLR inclination angles for 20 Seyfert 1 galaxies under the assumption that the BLR is disk-like. The derived inclination angles agree well with those derived previously by fitting the UV continuum and H emission line profiles. Adopting a relation between the FWHMs of [O III]5007 forbidden line and the stellar velocity dispersion, we also estimated the BLR inclinations for 50 narrow line Seyfert 1 galaxies (NLS1s). We found that the inclinations of broad Line Seyfert 1 galaxies (BLS1s) are systematically greater than those of NLS1s, which seldom exceed 30°. This may be an important factor that leads to the differences between NLS1s and BLS1s if the BLR of NLS1s is really disk-like.

Key words: galaxies: active --- galaxies: nuclei --- galaxies: Seyfert

PDF file (236 KB) | gzipped PS file ( 89 KB) | Back to Contents



Properties of Broad Band Continuum of Narrow Line Seyfert 1 Galaxies

Hong-Yan Zhou and Ting-Gui Wang (1,2)

Affiliation: (1) Center for Astrophysics, University of Science and Technology of China, Hefei 230026
             (2) National Astronomical Observatories, Chinese Academic of Science, Beijing 100012

E-mail:   mtzhou@mail.ustc.edu.cn  (corresponding author)

Abstract

We have performed a statistical study of the properties of the broad band continuum of Narrow Line Seyfert 1 galaxies (NLS1s) by collecting ratio, infrared, optical and X-ray continuum data from various databases and compared the results with control samples of Broad Line Seyfert 1 galaxies (BLS1s). We find that the fraction ( 6%) of Radio Loud (RL) NLS1s is significantly less than that of BLS1s ( 13%), which is caused by the lack of radio-very-loud sources in the former. The rarity of RL NLS1s, especially radio-very-loud ones, is consistent with the scenario of small black hole and high accretion rate for NLS1s. Six new radio loud NLS1s are found and five RL NLS1 candidates are presented. In comparison with the BLS1s, the NLS1s tend to have stronger far infrared emission, cooler infrared colors and redder B–K color, which suggests that NLS1s are hosted by dust-richer nuclei. The NLS1s also show steeper soft X-ray spectrum and large soft X-ray to optical flux ratio, while a significant fraction show flat soft X-ray spectra. At least two factors can account for this, absorption and spectral variability. We also perform a correlation analysis between various broad band data. It is found that most correlations identified for NLS1s are also valid for radio quiet BLS1s: (1) the optical colors are anti-correlated with X-ray spectral index; (2) higher optical, X-ray and NIR luminosity objects show bluer optical colors and red H–K color; (3) higher luminosity objects show warmer IRAS color; (4) the radio loudness correlates with B–K and X-ray to optical flux ratio. Radio loud objects behave somewhat differently in a few correlations.

Key words: galaxies: active --- galaxies: Seyfert --- radiation: continuum

PDF file (538 KB) | gzipped PS file (264 KB) | Table 1: PDF PS  | Back to Contents


Dynamical Evolution of Gamma-Ray Burst Remnants with Evolving Radiative Efficiency

Jin-Bo Feng
(1), Yong-Feng Huang (1,2,*), Zi-Gao Dai (1) and Tan Lu (1,2)

Affiliation: (1) Department of Astronomy, Nanjing University, Nanjing 210093
             (2) LCRHEA, Institute for High-Energy Physics, Chinese Academy of Sciences, Beijing 100039
                          
E-mail:   hyf@nju.edu.cn  (corresponding author)

Abstract

In previous works, a generic dynamical model has been suggested by Huang et al., which is shown to be correct for both adiabatic and radiative blastwaves, in both ultra-relativistic and non-relativistic phases. In deriving their equations, Huang et al. have assumed that the radiative efficiency of the fireball is constant. They then applied their model directly to realistic cases where the radiative efficiency evolves with time. In this paper, we abandon the above assumption and re-derive a more accurate dynamical equation for gamma-ray burst remnants. Numerical results show that the model presented by Huang et al. is accurate enough in general cases.

Key words: gamma rays: bursts --- hydrodynamics --- radiation mechanisms: nonthermal

PDF file (178 KB) | gzipped PS file (270 KB) | Back to Contents

How Fast Could a Proto-pulsar Rotate?

Ren-Xin Xu, Hong-Guang Wang and Guo-Jun Qiao


Affiliation:  Department of Astronomy, School of Physics, Peking University, Beijing 100871

E-mail:  rxxu@bac.pku.edu.cn   (corresponding author)
  
Abstract

According to two estimated relations between the initial period and the dynamo-generated magnetic dipole field of pulsars, we calculate the statistical distributions of pulsar initial periods. It is found that proto-pulsars are very likely to have rotation periods between 20 and 30 ms, and that most of the pulsars rotate initially at a period < 60 ms. Our result supports the asymmetric neutrino emission model for pulsar kick.

Key words: pulsars --- neutron stars --- magnetic fields

PDF file (168 KB) | gzipped PS file (582 KB) | Back to Contents

Energetics and Propagation of Coronal Mass Ejections in Different Plasma Environments

Jun Lin 

Affiliation:  Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
                         
E-mail: jlin@cfa.harvard.edu   

Abstract

Based on previous work, we investigate the propagation of CMEs in a more realistic plasma environment than the isothermal atmosphere, and find that it is a slightly faster reconnection for flux ropes to break free. The average Alfvén Mach number MA for the inflow into the reconnection site has to be at least 0.013 in order to give a plausible eruption (compared to MA=0.005 for the isothermal atmosphere). Taking MA=0.1, we find that the energy output and the electric field induced inside the current sheet match the temporal behavior inferred from the energetic, long duration, CME-associated X-ray events. The results indicate that catastrophic loss of equilibrium in the coronal magnetic field provides the most promising mechanism for major solar eruptions, and that the more energetic the eruption is, the earlier the associated flare peaks. The variation of the output power with the background field strength revealed by our calculations implies the poor correlation between slow CMEs and solar flares. This work also further confirms the explanation we proposed for the peculiar motion of giant X-ray arches and anomalous post-flare loops. Their kinematic pattern and observed heights are determined by the local Alfvén speed and its variation with height.

Key words: Sun: CMEs --- Sun: atmosphere --- Sun: magnetic fields

PDF file (301 KB) | gzipped PS file (417 KB)| Back to Contents

The Prediction of Maximum Amplitudes of Solar Cycles and the Maximum Amplitude of Solar Cycle 24

Jia-Long Wang (1), Jian-Cun Gong (2), Si-Qing Liu (2), Gui-Ming Le (2) and Jing-Lan Sun (1)

Affiliation:   (1) National Astronomical Observatories, CAS (NAOC), Beijing 100012, China
                 (2) Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100080
                    
E-mail: Jialongw@btamail.net.cn   (corresponding author)

Abstract

We present a brief review of predictions of solar cycle maximum amplitude with a lead time of 2 years or more. It is pointed out that a precise prediction of the maximum amplitude with such a lead-time is still an open question despite progress made since the 1960s. A method of prediction using statistical characteristics of solar cycles is developed: the solar cycles are divided into two groups, a high rising velocity (HRV) group and a low rising velocity (LRV) group, depending on the rising velocity in the ascending phase for a given duration of the ascending phase. The amplitude of Solar Cycle 24 can be predicted after the start of the cycle using the formula derived in this paper. Now, about 5 years before the start of the cycle, we can make a preliminary prediction of 83.2 –119.4 for its maximum amplitude.

Key words: Sun: sunspots -- Sun: activity

PDF file (146 KB) | gzipped PS file (363 KB) | Back to Contents
Inhomogeneity in Spectral Transmission of the Coated UBVRI Filters of BFOSC and its Influence on Photometry

Bao-An Yao (1) and Lin Huang (2)

Affiliation:   (1) Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030
             (2) National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012
                    
E-mail:  yba@center.shao.ac.cn   (corresponding author)

Abstract

In order to realize the Johnson UBV and Kron-Cousins RI photometric systems in BFOSC, glass filters were purchased according to the Bessell prescription. All the filters are anti-reflection coated on both sides to increase the transmission. By comparing two dome flat-field exposures taken through any one of these filters set in two orientations 90° apart, inhomogeneities in the filter transmission is clearly demonstrated. Using a PDS microphotometer, we have confirmed that the form of their spectral transmission curve varied from point to point on the filters. This kind of inhomogeneity cannot be eliminated by dividing by flat-fielding exposure and must be ascribed to inhomogeneities in the coating. This is not some accidental defect in coating, it is in the existing coating technique because all the filters (including the narrow-band interference ones) for the BFOSC and a H filter made by another manufacturer showed a similar pattern. We found that for the studies of variable stars with amplitudes less than 0.05 mag. or studies aiming at establishing accurate C-M diagrams of star clusters, the usual uncoated Schott glass filters of Bessell's prescription are to be preferred.

Key words: methods: data analysis --- techniques: photometric

PDF file (329 KB) | gzipped PS file (59 KB) | Back to Contents

ChJAA, 2002, Vol.2, No.6

Chinese Journal of Astronomy and Astrophysics: Online Edition

http://www.chjaa.org 

Copyright 2001--2008 All rights reserved. The National Astronomical Observatories of 
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