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1.
The coherent plasma process such as parametric decay instability (PDI) has been applied to a homogeneous and unmagnetized
plasma. These instabilities cause anomalous absorption of strong electromagnetic radiation under specific conditions of energy
and momentum conservation and thus cause anomalous heating of the plasma. The maximum plasma temperatures reached are functions
of luminosity of the radio radiation and plasma parameters. We believe that these processes may be taking place in many astrophysical
objects. Here, the conditions in the sources 3C 273, 3C 48 and Crab Nebula are shown to be conducive to the excitation of
PDI. These processes also contribute towards the absorption of 21cm radiation 相似文献
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王建民 《紫金山天文台台刊》1999,18(3):271-273
频繁的超新星爆发可用以解释活动星系核与类星体的超高金属丰度。星团中的恒星与吸积盘相互作用导致致密天体中子星和黑洞的形成率很高,这些致密天体与红巨星很容易形成双星系统,而后形成（ＮＳ／ＢＨ,ＮＳ／ＢＨ） 双星由于引力辐射最终导致并合而形成伽玛射线爆发。我们估计了伽玛射线爆的爆发频率,发现与观测相符。 相似文献
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During the ROSAT All-Sky Survey (RASS; Voges 1992, 1997) about 80,000 X-ray sourceswith a detection likelihood 2 10 were detected, from which 18,811 sources having a PSPC countrate larger than 0.05 ets s--1 and detection likelihood 3 15 were compiled in the RASS-BSC(VOges et al. 1996a). More than 65% RASS sources remain unidentified (Voges et al. 1996b).The optical spectroscopic study of these RASS sources is essential for understanding them moreclearly.The idelltification of X-… 相似文献
4.
The data of light variations of six blazars with low peak frequencies (i.e., BL Lacerta, 0235+164, OQ530, 0716+714, 3C 345, and 3C 273) at 4.8, 8, 14.5, 22 and 37 GHz in the recent thirty years have been collected from immense amount of literature. By using the method of discrete correlation function the correlations and delays of the light curves of these six sources at the 5 wavebands are analyzed. With the method of structural function, the periods and timescales of the light variations of these six sources are analyzed, and their amplitudes of light variations are compared and analyzed. As revealed by the result of analysis, among the six blazars the amplitudes of light variations of 0716+714 and 0235+164 are relatively large, and those of 3C 345 and OQ 530 are less. The amplitudes of light variations of 3C 273 and BL Lacertae are relatively smaller. As shown by the multi-waveband analysis of delays between two neighboring wavebands, 0235+164 exhibits the tendency of variation that the high-frequency wavebands precede the low-frequency wavebands. On the whole, 3C 345 exhibits the tendency that the high-frequency wavebands lag be-hind the low-frequency wavebands. The analyses of the other blazars show that in a part of radio wavebands there appears the tendency of variation that the high-frequency waveband leads the low-frequency waveband. Yet in the other radio wavebands there appears the tendency that the high-frequency waveband lags behind the low-frequency waveband. As revealed by the results of analyses with the method of structural function, the timescale, fitted slope, and period of light variations of 3C 345 are larger than those of the other five blazars with low peak frequencies. This demonstrates that the activity of 3C 345 is comparatively weaker than the other five sources, and implies that in the interior of 3C 345 there may exist some physical processes which are different from those of the other five blazars with low peak frequencies. 相似文献
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We report the Balmer broad absorption lines (BALs) in the quasar SDSS J2220 + 0109 discovered from the SDSS data, and present a detailed analysis of the peculiar absorption line spectrum, including the He I* multiplet at λλ3189, 3889 arising from the metastable 23s-state helium and the Balmer Hα and Hβ lines from the excited hydrogen H I of n = 2 level, which are rarely seen in quasar spectra, as well as many absorption lines arising from the excited Fe II* of the levels 7 955 cm−1, 13 474 cm−1 and 13 673 cm−1 in the wavelength range 3100∼3300 Å. Ca II H, K absorption line doublets also clearly appear in the SDSS spectrum. All absorption lines show a similar blueshifted velocity structure of Δv ≈ − 1500 ∼ 0 km·s−1 relative to the quasar's systematic redshift determined from the emission lines. Detailed analysis suggests that the Balmer absorption lines should arise from the partially ionized region with a column density of NHI ≈ 1021 cm−2 for an electron density of ne ∼ 106 cm−3; and that the hydrogen n = 2 level may be populated via collisional excitation with Lyα pumping. 相似文献
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利用基于自校正和ＣＬＥＡＮ算法的现代ＶＬＢＩ混合成图技术,对Ｐｅａｒｓｏｎ等人于１９７６年观测得到的类星体 ３Ｃ ２８６在 １８ ｃｍ波段上的 ＶＬＢＩ数据重新作了处理．由此得到的图像要大大好于最初的处理结果,也获得了更多的有用信息．用几个Ｇａｕｓｓ模型去拟合校正后的ＵＶ数据,发现中央亮区可以被分解为两个致密结构,这与后来的高分辨率观测相一致．与不同历元的ＶＬＢＩ观测结果相比较,发现这两个致密结构间的距离不但在同一时间随观测频率变化,而且很有可能在同一观测频率上随时间变化． 相似文献
10.
D. A. Varshalovich A. V. Ivanchik P. Petitjean R. Srianand C. Ledoux 《Astronomy Letters》2001,27(11):683-685
Having analyzed the spectrum of the quasar PKS 1232+0.82 taken by Petitjean et al. (2000), we identified HD molecular lines in an absorption system at redshift z=2.3377. We estimated the column density of HD molecules in this system, N(HD) = (1?4) × 1014cm?2. The excitation temperature of the first rotational level J=1 relative to the ground state J=0 is T ex=70 ± 7 K. As far as we know, this is the first detection of HD molecules at high redshift. 相似文献