Diurnal Effects

- The plots are for successive days.
- Vertical axis: Square of the (4 successive time sample average of the cross-correlation of delay bin 16)
- Horizontal axis: Right Ascension in decimal hours
- The two telescopes were fixed, pointing South to 40 degree N declination.
- Baseline is almost exactly East-West with 22 km spacing.
- Filter bandwidth is +-1.25 MHz around 2.7 GHz.
- Doppler shift of -9.3 Hz was entered into the LL local oscillator.
- Multiple peaks per object are expected from the double-sideband cross-correlator we use.
- Antenna beamwidth is approximately 1 degree.

Note the large peak near 10.78 RA. A similar peak is present the next day close to the same spot in the sky. Other peaks seem to match although the multiple peaks appear a little different between the two days. The variation in level from day to day may be primarily due to added noise. The variation is large because the vertical axis is the square of the cross-correlation. If the pattern repeats on future days, we may be looking at a radio object near 10.78 RA. Another object may be present at 10.38 RA. According to the GB6 catalog, the 10.38 object may be the object catalogued as 32621. It has 789 milliJanskys flux (obtained from the database). It's Galactic Latitude is 56.9 degrees and Galactic Longitude is 180.9 degrees. It may be a supernova remnant, but is more likely a Quasar (thought to be a massive black hole in a galaxy) very far outside the Milky Way Galaxy.

Mabuhay crosscorrelator Julian Day 2451515

Mabuhay crosscorrelator Julian Day 2451516

Note: the horizontal scales above and below are slightly different.
The following plot is from the VizieR GB6 database. http://adc.gsfc.nasa.gov/viz-bin/VizieR (then enter GB6 into 1.) Gregory P.C., Scott W.K., Douglas K., Condon J.J., Astrophys. J. Suppl. Ser. 103, 427 (1996).
Only objects stronger than 300 milliJanskys are plotted. And the declination range is limited to 36 to 44 degrees. Several of the objects in the data plotted above seem to appear at the same location in the GB6 database.
One Jansky is 10^-26 watts per square meter of aperture, per Hz of receiver bandwidth.
It is interesting that the object supposedly at 10.8 hours seems to be quite strong, and is not above 300 milliJanskys in the GB6 database. I looked at the GB6 database below 300 milliJanskys. There are a two objects around 10.8 hours at 205 and 234 milliJanskys. Perhaps the large fluctuation in the measurement using the Mabuhay cross-correlator can explain the differences. However, when examining the other signals as a calibration attempt, the object at 10.8 hours just seems too strong over two days to support this explanation. We'll get more data to see what is going on. And everything needs to be double-checked.

VizieR GB6 database Gregory P.C., Scott W.K., Douglas K., Condon J.J.,
Astrophys. J. Suppl. Ser. 103, 427 (1996)