| Multifrequency Polarization Variations in the Quasar 0917＋624 |
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| 作者姓名： | Shan-Jie Qian A. Kraus Xi-Zhen Zhang T. P. Krichbaum A. Witzel and J. A. Zensus National Astronomical Observatories Chinese Academy of Sciences Beijing Max-Planck-Institut fur Radioastronomie Auf dem Hugel Bonn Germany |
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| 作者单位： | Shan-Jie Qian，A. Kraus，Xi-Zhen Zhang，T. P. Krichbaum，A. Witzel and J. A. Zensus National Astronomical Observatories，Chinese Academy of Sciences，Beijing 100012 Max-Planck-Institut fur Radioastronomie，Auf dem Hugel 69，53121 Bonn，Germany |
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| 摘 要： | We present a detailed analysis of multi-frequency observations of linear polarization in the intraday variable quasar 0917+624 (z = 1.44). The observations were made in May 1989 at five frequencies (1.4, 2.7, 5.0, 8.3 and 15GHz) with the VLA and the Effelsberg 100 m-telescope and in December 1988 at two frequencies (2.7 and 5.0 GHz) with the latter. It is shown that the relationship between the variations of the polarized and total flux density is highly wavelength dependent, and the multi-frequency polarization behavior may be essential for investigating the mechanisms causing these variations. It is shown that the variations observed at 20 cm can be interpreted in terms of refractive interstellar scintillation. However, after subtracting the variation due to scintillation, three 'features' emerged in the light-curve of the polarized flux density, indicating an additional variable component. Interestingly, these features are shown to be correlated with the variations at 2-6 cm, thus indicating that thes
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| 关 键 词： | 银河系 磁场 极化 无线电 类星体 |
Multifrequency Polarization Variations in the Quasar 0917+624 |
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| Shan-Jie Qian,A. Kraus,Xi-Zhen Zhang,T. P. Krichbaum,A. Witzel and J. A. Zensus National Astronomical Observatories,Chinese Academy of Sciences,Beijing Max-Planck-Institut fur Radioastronomie,Auf dem Hugel , Bonn,Germany.Multifrequency Polarization Variations in the Quasar 0917+624[J].Chinese Journal of Astronomy and Astrophysics,2002,2(4):325-346. |
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| Authors: | Shan-Jie Qian AKraus Xi-Zhen Zhang TPKrichbaum AWitzel JAZensus |
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| Abstract: | We present a detailed analysis of multi-frequency observations of linear polarization in the intraday variable quasar 0917+624 (z = 1.44). The observations were made in May 1989 at five frequencies (1.4, 2.7, 5.0, 8.3 and 15 GHz) with the VLA and the Effelsberg 100m-telescope and in December 1988 at two frequencies (2.7 and 5.0 GHz) with the latter. It is shown that the relationship between the variations of the polarized and total flux density is highly wavelength dependent,and the multi-frequency polarization behavior may be essential for investigating the mechanisms causing these variations. It is shown that the variations observed at 20cm can be interpreted in terms of refractive interstellar scintillation. However,light-curve of the polarized flux density, indicating an additional variable component. Interestingly, these features are shown to be correlated with the variations at 2-6 cm, thus indicating that these features and the associated variations are due to some intrinsic causes. Moreover, a very rapid polarization angle swing of ～ 180°observed in December 1988 which cannot be explained by refractive interstellar scintillation, may also be produced by an intrinsic mechanism. Accordingly, we use a shock model to explain the polarization variations observed at the higher frequencies, although scintillation could also exist. The shock model can explain not only the variation of intensity, but also the time variation of its degree and angle of polarization, including the rapid swing of the polarization angle. It is shown that the degree and angle of polarization of the shock need only vary slightly in order to account for the observed complicated behaviour of polarization. |
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| Keywords: | radio continuum: galaxies - polarization - quasars: individual (QSO0917+624) |
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