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On Rapid Interstellar Scintillation of Quasars: PKS 1257-326 Revisited

Published online by Cambridge University Press:  20 April 2012

Hayley E. Bignall  and
Jeffrey A. Hodgson
Hayley E. Bignall
Affiliation:
International Centre for Radio Astronomy Research, Curtin University, WA 6845, Australia email: H.Bignall@curtin.edu.au
Jeffrey A. Hodgson
Affiliation:
International Centre for Radio Astronomy Research, Curtin University, WA 6845, Australia email: H.Bignall@curtin.edu.au
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Abstract

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The line of sight towards the compact, radio loud quasar PKS 1257–326 passes through a patch of scattering plasma in the local Galactic ISM that causes large and rapid, intra-hour variations in the received flux density at centimetre wavelengths. This rapid interstellar scintillation (SS) has been occurring for at least 15 years, implying that the scattering “screen” is at least 100 AU in physical extent. Through observations of the ISS we have measured microarcsecond-scale “core shifts” in PKS 1257-326, corresponding to changing opacity during an intrinsic outburst. Recent analysis of VLA data of a sample of 128 quasars found 6 sources scintillating with a characteristic time-scale of < 2 hours, suggesting that nearby scattering screens in the ISM may have a covering fraction of a few percent. That is an important consideration for proposed surveys of the transient and variable radio sky.

Keywords

techniques: high angular resolutionISM: structurequasars: individual
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 7 , Symposium S285: New Horizons in Time-Domain Astronomy , September 2011 , pp. 129 - 132
Copyright
Copyright © International Astronomical Union 2012

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