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Project MK22: YSO G188.94+0.89 at methanol line CH3OH 12.178 GHz





With the Sao Giao radio telescope and an Astra standard LNB we captured methanol CH3OH of the young stellar object(YSO) G188.94+0.89, see plot. In the literature it says to have a VLSR velocity of +10km/s and an intensity of 183jy.

raw line

Fig.1 - G188 Raw line and noise







all lines

Fig.2 - G188 all 5 minutes integration lines









g188 sum

Fig.3 - G188 sum, average



In the beginning, or you can say for a week, I did not see a result, until it was noticed that the pointing parms were E1950 and not E2000.
With the dish of 9.3m and a 0.15deg beam we were looking in the wrong direction.
So if you find a paper like below, check the pointing reference.


With the source velocity = +10km/s from that paper and the calculation of our own solar system VLSR=-17km/s in the source direction, the total velocity is 10-17=-7km/s.
Now we can calulate the sky frequency where the signal can be captured.
In a speadsheet you can calculate it to be (rest freq)*(1-(tot velocity)*1000/c=12.178879364GHz with the rest freq=12.178595GHz.
The local oscillator of the LNB is 10.6GHz, so the output freq for the dongle should be 1.578879364GHz, but check it with an (overtone) oscillator.

Next check with Sharp# for the right level and no RFI, and start your cfrad2.exe. Each line is the mean of E5 spectra written to disk.
Four summed lines (green to purple) (dish offset) are used as reference; the bottom line is the average of the 6 next lines; total 30min of integration.
When zoomed in, you can see that the left and right edges are a bit higher; these are caused by the masing of the circumstellar disk.
One side approaching and the other side is receiding us.
Strong masers are mostly seen on the edge, because the colomn of gas is then longest and masing amplification is maximum.




disk masing

Fig.3 - Circumstellar disk masing



When you take the frequency difference between the left and the right peak and calculate the disk rotational speed, it is low for methanol; just about 1km/s.
So, the distance to the "star to be born" must be huge, because even the rotational speed of pluto is about 5km/s.


On ignition the star will disintegrate the gas disk cloud so only the solid clumps remain, which form planets.




gas evaporation

Fig.3 - Evaporation of the disk gas



In the zip files I added all the referenced papers here in a zip file.





Some more info about the system.


The angle encoders are analog sin/cos resolvers wired to a 16 bit AD2S80 R/D converter.
Data is serialized by a PIC and send to a second PIC processor. The pointing sw is based on python (see http://parac.eu/projectmk8.htm) and run on a PC with inet time sync.
The 'set' data is also send to the second PIC. Monitoring/command output/input of the PIC servo software is communicated to that PC.
The second PIC with the servo sw also generates a PWM signal for both channels and send them via optocouplers out to two frequency inverters which drive the motors.
The sw servo program react to differences of 0.01 degree or more.
All software was home made.









Michiel Klaassen november 2016