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Abstract:
In this work I have undertaken a detailed investigation of the BL Lac
object PKS B1144−379. This project utilised high-cadence flux density
monitoring of interstellar scintillation with the University of
Tasmania Ceduna 30m radio telescope at a frequency of 6.7 GHz. A
complementary kinematic study of the sub parsec-scale jet of PKS
B1144−379 has been undertaken, using 8.6 GHz Very Long Baseline
Interferometry (VLBI) data. The centimetre wavelength radio flux
density of this source is known to vary on a range of timescales from
a few days up to several months. The rapid (timescales of less than a
day), apparent variability of this compact extragalactic radio source
at radio wavelength is known as intraday variability (IDV). The
current investigation shows conclusively that the rapid variability is
the result of a propagation effect known as interstellar scintillation
(ISS), which originates in the inhomogeneous interstellar medium
(ISM). On the other hand, the long-term variability (months to years)
suggests that the source also exhibits substantial intrinsic
evolution. (Image Credit: NASA / Dana Berry, SkyWorks Digital)
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