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          Institute: MPI für Radioastronomie     Collection: Publikationen des MPI für Radioastronomie     Display Documents

ID: 12209.0, MPI für Radioastronomie / Publikationen des MPI für Radioastronomie
Multifrequency polarization variations in the quasar 0917+624
Authors:Qian, S. J.; Kraus, A.; Zhang, X. Z.; Krichbaum, T. P.; Witzel, A.; Zensus, J. A.
Date of Publication (YYYY-MM-DD):2002-08
Title of Journal:Chinese Journal of Astronomy and Astrophysics
Journal Abbrev.:Chin. J. Astron. Astrophys.
Issue / Number:4
Start Page:325
End Page:346
Review Status:Peer-review
Audience:Experts Only
Abstract / Description: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 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 these features and the associated variations are due to some intrinsic causes. Moreover, a very rapid polarization angle swing of similar to180 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.
Free Keywords:radio continuum : galaxies; polarization; quasars : individual (QSO 0917+624)
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Radioastronomie
External Affiliations:Chinese Acad Sci, Natl Astron Observ, Beijing 100012, Peoples R; China; Chinese Acad Sci, Natl Astron Observ, Beijing 100012, Peoples R China; Max Planck Inst Radioastron, D-53121 Bonn, Germany
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