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

ID: 11190.0, MPI für Radioastronomie / Publikationen des MPI für Radioastronomie
Annual modulation in the variability properties of the IDV source 0917+624?
Authors:Fuhrmann, L.; Krichbaum, T. P.; Cimò, G.; Beckert, T.; Kraus, A.; Witzel, A.; Zensus, J. A.; Qian, S. J.; Rickett, B. J.
Date of Publication (YYYY-MM-DD):2002
Title of Journal:Publications of the Astronomical Society of Australia
Journal Abbrev.:Publ. Astron. Soc. Aust.
Issue / Number:1
Start Page:64
End Page:68
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:There is new evidence which identifies seasonal changes of the variability time scale in intraday variable (IDV) sources with refractive interstellar scintillation effects. Such a RISS model takes the annual change of the Earth's velocity relative to the scattering medium into account. In September 1998 we found a remarkable prolongation of the variability time scale in the IDV source 0917 + 624 with only small variations in flux density during a period of 5 days. This was explained as a seasonal effect, in which the velocity vector of the Earth and the interstellar medium nearly cancelled. In order to further investigate the applicability of the model for 0917 + 624, we performed an Effelsberg 6 cm- flux monitoring program over the course of one year. Since September 2000, the source appears to be remarkably inactive and yet (May 2001) no return to its normal, faster and stronger variability pattern is observed. Here, our observational results and a possible explanation for the current quiescence are presented.
Free Keywords:quasars : individual (0917+62); radio continuum : ISM; scattering
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Radioastronomie
External Affiliations:Max Planck Inst Radioastron, Hugel 69, D-5300 Bonn, Germany; Max Planck Inst Radioastron, D-5300 Bonn, Germany; Chinese Acad Sci, Beijing Astron Observ, Beijing 100080, Peoples R China; Univ Calif San Diego, San Diego, CA 92103 USA
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