Point source

[John Hughes <jackph@physics.rutgers.edu>]

Dear all:

I looked at the point source in the 50 and 40 ks observations from
Feb and Apr this year.  In each case the point source appears extended.
In the Feb observation, the source is 1.9' offaxis, while it
is 2.4' off-axis in the Apr one. I ran a couple of ChaRT simulations 
that strongly indicate that the extension seen in both observations
is due to the PSF.  You can see the mosaic of actual and simulated
images at my web site:

http://www.physics.rutgers.edu/~jackph/casa_vlp/ptsrc_mosaic.jpg

The "postcard" images are all to the same scale and are oriented in 
the usual way (N: up; E: left). Each postcard is about 20" in size.
The relative orientation of the apparent "extension" (rotated about
90 degrees) is due nearly entirely to the difference in roll angles 
(~90 degrees).  By the way the mean position of the point source is
R.A. = 23:23:27.921, Decl.= +58:48:42.46 in the February observation and 
R.A. = 23:23:27.913, Decl.= +58:48:42.34 in the April one.  This is
just straight out of the L2 events file - no corrections have been
applied.

Cheers,
Jack

_______________________________________________________________________________
John P. Hughes          Department of Physics and Astronomy
                        Rutgers, The State University of New Jersey
                        136 Frelinghuysen Road, Piscataway, NJ 08854-8019 USA
                        Phone: 732-445-0980, Fax: 732-445-4343
                        http://www.physics.rutgers.edu/~jackph