[daip] [!12656]: AIPS - Offset source moving in RA during observation

[Andy Biggs]

Andy Biggs updated #12656
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              Status: Open (was: On Hold)

Offset source moving in RA during observation
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           Ticket ID: 12656
                 URL: https://help.nrao.edu/staff/index.php?/Tickets/Ticket/View/12656
                Name: Andy Biggs
       Email address: abiggs at eso.org
             Creator: User
          Department: AIPS Data Reduction
       Staff (Owner): -- Unassigned --
                Type: Issue
              Status: Open
            Priority: Default
                 SLA: NRAO E2E
      Template group: Default
             Created: 07 September 2018 04:11 PM
             Updated: 13 May 2020 01:57 PM
           Reply due: 15 May 2020 01:57 PM (2d 0h 0m)
      Resolution due: 27 April 2022 12:00 AM (713d 10h 3m)

Hello again,
Could this ticket actually be assigned to someone? I've got some new VLBI data on this source (EVN at 5 GHz observed 1 year ago) and am seeing the same thing. So, this is a different array at a different frequency but again processed in AIPS. There is I suppose still the possibility that this has some physical origin but the phase slopes seen on the longest baselines are suspiciously linear.
To recap, I have a lens with two images (A and B) separated by 1.5". The flux ratio is high, ~10:1 and the weak image (B) looks pretty terrible. If I subtract the clean components from the bright image and then self-cal B (this is essentially peeling) then a subsequent map of B looks fantastic. I attach a pdf that shows the images and the phase solutions that B seems to require that A doesn't. Peeling a source 1.5" away from the phase centre shouldn't, of course, be necessary.
I have not yet checked to see if B appears, as before, to be drifting in R.A. but will do so.
Thanks,
Andy

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