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Rapid Variability and Annual Cycles in the Characteristic Timescale of the Scintillating Source PKS 1257-326


Bignall, HE and Jauncey, DL and Lovell, JEJ and Tzioumis, AK and Kedziora-Chudczer, L and Macquart, JP and Tingay, SJ and Rayner, DP and Clay, RW, Rapid Variability and Annual Cycles in the Characteristic Timescale of the Scintillating Source PKS 1257-326, The Astrophysical Journal, 585, (2 I) pp. 653-664. ISSN 0004-637X (2003) [Refereed Article]

DOI: doi:10.1086/346180


Rapid radio intraday variability (IDV) has been discovered in the southern quasar PKS 1257-326. Flux density changes of up to 40% in as little as 45 minutes have been observed in this source, making it, along with PKS 0405-385 and J1819+3845, one of the three most rapid IDV sources known. We have monitored the IDV in this source with the Australia Telescope Compact Array (ATCA) at 4.8 and 8.6 GHz over the course of the last year and find a clear annual cycle in the characteristic timescale of variability. This annual cycle demonstrates unequivocally that interstellar scintillation is the cause of the rapid IDV at radio wavelengths observed in this source. We use the observed annual cycle to constrain the velocity of the scattering material and the angular size of the scintillating component of PKS 1257-326. We observe a time delay, which also shows an annual cycle, between the similar variability patterns at the two frequencies. We suggest that this is caused by a small (∼10 μas) offset between the centroids of the 4.8 and 8.6 GHz components and may be due to opacity effects in the source. The statistical properties of the observed scintillation thus enable us to resolve source structure on a scale of ∼10 μas, resolution orders of magnitude higher than current VLBI techniques allow. General implications of IDV for the physical properties of sources and the turbulent interstellar medium are discussed.

Item Details

Item Type:Refereed Article
Research Division:Physical Sciences
Research Group:Astronomical sciences
Research Field:Galactic astronomy
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the physical sciences
UTAS Author:Lovell, JEJ (Dr Jim Lovell)
ID Code:45344
Year Published:2003
Web of Science® Times Cited:107
Deposited By:Physics
Deposited On:2007-07-11
Last Modified:2007-07-11

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