[GMVAtech 22] Re: 7mm Sio pointing at VLBA

[Thomas Krichbaum]

Hi,

from 2 GMVA paper drafts, which I recently got to for internal comment,
I realize that the PIs come up with gain correction factors for the VLBA
of typically 2. That means the VLBA is calibrated low.  These gain
corrections are derived from the amplitude self-calibration during the
imaging and by comparing with the European stations, which are sometimes
better calibrated.  A comparison with near in time 7mm VLBA maps from
the BU group also shows that the flux in the 3mm GMVA maps often is
about a factor of 2 low. For the a-priori calibration we use the DPFUs
from  /pub/vlba_gains.key.

Could it be that the DPFUs are not correct any more, or is there an
another reason for a lower VLBA sensitivity at 3mm?

best Thomas







On 09/20/2018 09:34 PM, Vivek Dhawan wrote:
> Greetings, Thomas!
> 
> not much in the way of frequent VLBA 7mm fluxes, but here is
> what we have. Not much good-weather time is available for
> single-dish VLBA work, Yebes sounds like a much better idea!
> 
> http://www.aoc.nrao.edu/%7Evdhawan/7mm_flux.html
> 
> I'll make sure we use your latest catalog.
> 
> On 09/20/2018 11:13 AM, Thomas Krichbaum wrote:
>> Dear Mark,
>>
>> I just want to give a pre-warning, that the GMVA schedule will be
>> updated once more on next Monday.
>>
>> We are updating the list of bright SiO maser sources, which will be used
>> for the 7mm line pointing in the gaps between the VLBI scans.
>>
>> Over the weekend, the 40m Yebes telescope will provide new Sio maser
>> fluxes, which I plan to include in the GMVA schedule on Oct. 24 (next
>> Monday).
>>
>> In 3mmpeak_RDBE_PFB.cmd:
>>
>>   srcfile = 3mmsources.pointing ! Local file Reference pointing sources
>>
>> (see here: http://www.vlba.nrao.edu/astro/VOBS/astronomy/sep18/c182a ).
>>
>> This is nothing new and we have used it in the past, but I just want to
>> make sure that the VLBA system uses THIS catalogue and NOT the default
>> catalogue (which is $SCHED/catalogs/sources.pointing).
>>
>> best Thomas
>>
>>

-- 
Dr. Thomas P. Krichbaum
Max-Planck-Institut fuer Radioastronomie
Auf dem Huegel 69
D-53121 Bonn / Germany

Mail: tkrichbaum at mpifr-bonn.mpg.de
Tel.: (Germany +49)-228-525-295
Web : http://www.mpifr-bonn.mpg.de/research/vlbi