PKS 0637-752 (z=0.656) is another of the strong, flat-spectrum radio sources
considered by von Montigny et al. [1995b] in their investigation
of radio sources not identified by EGRET.
von Montigny et al. [1995b] place an upper limit of 1.5 
10 
cm 
s 
in greater than 100 MeV gamma-rays from the
direction of this AGN.
Figure: Low contour, 
1%. Peak, 3.6 Jy/beam. Beam, 1.9 0.6 mas @ 7.3 
.
The compact structure of the radio source was first revealed by Preston
et al. [1989] with 2.3 GHz VLBI observations utilising the
SHEVE array. They reported an essentially unresolved component with a
2.6 Jy core and a halo of emission greater than 20 mas in extent with a flux density of 1.5
Jy. The latest VLBI observations (Figure 4.10) at the higher frequency
of 4.8 GHz show that the compact radio structure is dominated by a
bright core and a jet lying at a position angle of approximately
. Two-frequency imaging of the kpc-scale radio
structure with the ATCA [Lovell, McCulloch, & Jauncey 1995] shows a strongly one-sided jet
which lies at a position angle of approximately 
. The
mas-scale and arcsecond-scale radio structures are very well
aligned, the difference in position angle being approximately
4 .
From Figure 4.10, the core FWHM and total flux density,
de-convolved from the restoring beam, have been estimated at 0.4
0.4 mas and 4.3 Jy respectively, leading to a value for the observed radio core brightness
temperature of approximately 1.5 10 
K at the frequency
of 4.8 GHz. The source frame brightness temperature is therefore approximately 
K, again at or in excess of the inverse Compton limit for synchrotron radiation.
Again the mismatch in resolution and data quality between this image and the model of Preston et al. [1989] do not allow a useful estimate of apparent motion to be made for this source.