These are the latest articles published in Chinese Journal of Astronomy and Astrophysics.

• Open/close The Spectral Energy Distributions of Different Types of Seyfert Galaxies

  Ran Wang and Xue-Bing Wu 2005 Chin. J. Astron. Astrophys. 5 299 Tag this article

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  We calculated the average spectral energy distributions (SEDs) for Seyfert 1 galaxies (S1s) and two types of Seyfert 2 galaxies (S2s with or without polarized broad-line regions, i.e. HBLRs and Non-HBLRs). We found that compared with other Seyfet galaxies, the Non-HBLRs show an extremely brighter feature towards the far infrared band, which is believed to be affected by the circumnuclear starburst components. The energy in this band seems to dominate their bolometric luminosities. A weaker hard X-ray emission was also found in these Non-HBLRs, which is believed to be the indicator of a weaker nuclear power. So in the case of Non-HBLRs, any use of bolometric luminosities to represent the active galactic nuclei (AGN) power is possibly misleading.

• Open/close Gamma-Ray Spectral Characteristics of Thermal and Non-Thermal Emission from Three Black Holes

  James C Ling and William A Wheaton 2005 Chin. J. Astron. Astrophys. 5 80 Tag this article

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  Cygnus X-1 and the gamma-ray transients GRO J0422+32 and GRO J1719-24 displayed similar spectral properties when they underwent transitions between the high and low gamma-ray (30 keV to few MeV) intensity states. When these sources were in the high γ-ray intensity state (γ ₂, for Cygnus X-1), their spectra featured two components: a Comptonized shape below 200-300keV with a soft power-law tail (photon index >3) that extended to ~1MeV or beyond.When the sources were in the low-intensity state (γ ₀, for Cygnus X-1), the Comptonized spectral shape below 200 keV typically vanished and the entire spectrum from 30 keV to ~1MeV can be characterized by a single power law with a relatively harder photon index ~2–2.7. Consequently the high- and low-intensity gamma-ray spectra intersect, generally in the ~400 keV – ~1MeV range, in contrast to the spectral pivoting seen previously at lower (~10 keV) energies. The presence of the power-law component in both the high- and low-intensity gamma-ray spectra strongly suggests that the non-thermal process is likely to be at work in both the high and the low-intensity situations. We have suggested a possible scenario (Ling & Wheaton, 2003), by combining the ADAF model of Esin et al. (1998) with a separate jet region that produces the non-thermal gamma-ray emission, and which explains the state transitions. Such a scenario will be discussed in the context of the observational evidence, summarized above, from the database produced by EBOP, JPL's BATSE earth occultation analysis system.

• Open/close Detecting sub-mJy sources with the EVN

  Zsolt Paragi et al 2005 Chin. J. Astron. Astrophys. 5 359 Tag this article

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  Some microquasars are permanently bright radio sources while others are faint but produce powerful radio outbursts. Most of the X-ray binaries (XRB) however are very faint or undetected in the radio regime. The European VLBI Network (EVN) recently introduced the Mark5 recording system which allows data rates of up to 1 Gbit s ^-1. This increases the sensitivity of the array significantly. We briefly describe recent developments in the EVN in terms of reliability of the network and also data quality. We demonstrate the power of the EVN in detecting sub-mJy radio sources with modest integration times (order of hours). This high sensitivity capability will permit the study of variable Galactic sources at milli-arcsecond resolution. An estimate is given for the lowest detectable mass of hypothetical intermediate-mass black holes (IMBH) in nearby galaxies, provided these are located in radio-jet systems analogous to microquasars and active galactic nuclei.

• Open/close Outflows and Inflows in Astrophysical Systems

  Yue Shen and Yu-Qing Lou 2005 Chin. J. Astron. Astrophys. 5 241 Tag this article

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  We seek for self-similar solutions describing the time-dependent evolution of self-gravity systems with either spherical symmetry or axisymmetric disk geometry. By assuming self-similar variable x ≡ r/at where a is isothermal sound speed we find self-similar solutions extending from the initial instant t = 0 to the final stage t → ∞ using standard semi-analytical methods. Different types of solutions are constructed, which describe overall expansion or collapse, envelope expansion with core collapse (EECC), the formation of central rotationally supported quasi-equilibrium disk as well as shocks. Though infinitely many, these self-similarity solutions have similar asymptotic behaviors which may impose diagnosis on the velocity and density structures in astrophysical systems.

• Open/close Microquasars as High-energy Gamma-ray Sources

  Josep M Paredes 2005 Chin. J. Astron. Astrophys. 5 121 Tag this article

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  Galactic microquasars are certainly one of the most recent additions to the field of high energy astrophysics and have attracted increasing interest over the last decade. However, the high energy part of the spectrum of microquasars is the most poorly known, mainly due the lack of sensitive instrumentation in the past. Microquasars are now primary targets for all of the observatories working in the X-ray and gamma-ray domains. They also appear as the possible counterparts for some of the unidentified sources of high-energy gamma-rays detected by the experiment EGRET on board the satellite COMPTON-GRO. This paper provides a general review of the main observational results obtained up to now as well as a summary of the scenarios for production of high-energy γ-rays at the present moment.