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Disney Prophecy
The Plutonian
Chronicles
Intro.
Pulsars are formed when supernovae go
BOOM!!! After the star explodes a neutron
star is formed. A pulsar is a neutron star
that emits all kinds of energy as it spins. It
is extremely dense (~ 1.0 x 1015 kg m-3 ),
reaches speeds to up to 1,000 km/sec,
and they have periods ranging from 1.4
ms to 8.5 sec.
Methodology
When determining whether or not a certain plot is
a pulsar or just RFI, there are certain things you
should be looking for. First off, it must have a
DM(dispersion measure) of more than zero. If it
is zero, the transmission is coming from Earth.
Secondly, look at the reduced x2 on the DM
chart. If it is less than the number one, there is a
great chance that it is not a pulsar. You also
need to check out the pulsar profile. If there are
many rapid and spikes and drops, it might not
come out to be a pulsar, just noise.
Noise
Noise is useless information. It’s a signal
that is all static, and it appears to have no
definite pattern.
In this candidate all you can clearly see is
that it is pure NOISE!!!
RFI
RFI stands for radio frequency interference.
It can disrupt the radio waves coming from
pulsars, thus not showing a clear image of
the pulsar. RFI is caused by any device
that has an electric charge (i.e. iPods, cell
phones, or pagers).
One of the dead giveaways of RFI is if you look at the reduced chi
squared in the DM chart. It is very rare for a pulsar to have a reduced
chi squared of less than the number 1.
On this candidate you can clearly see that in the S-Band, the frequency
is 350 and runs horizontally. This makes it narrow-banded, and is not a
pulsar but RFI. In the pulse profile you can’t see anything but pure
noise.
Another good example of RFI is a high dispersion measure. On
average, the DM of a pulsar is ~ 50. As you can see, 507.200 is
extremely high.
This candidate has dark spots that only show up around the 50
seconds in the time versus phase graph. Since the spots are smeared
it is probably interference.
This graph looks like a pulsar except for the sub-band. Everything is
consistent, but the only frequency it comes in at is 370 MHz. If this
were a pulsar, then the frequency would have to be much lower to have
such big pulses.
This candidate has a DM of 0. The time versus phase graph has no
apparent pattern and it curves.
Good Candidates
A good candidate for a pulsar is a lot
different than a bad one. It must have a
broadband in the Sub-band chart, a
decent pulsar profile, and a DM ~ 50. It
usually shows up throughout the whole
observation time, but is also acceptable if
it doesn’t show up through-out the whole
observation. Again, most pulsars do not
have a reduced chi squared of less than
one on the DM chart.
This pulsar looks to be a pretty good candidate. The pulsar profile shows a prominent
peak. The time vs. phase graph and the sub-band graph correspond with the pulses, but
are very weak. The DM of this graph is 52.547, which is very good. Ultimately this graph
candidate has good potential and should be observed again.
This is a good candidate for a pulsar because it has a good high peak
in the pulsar profile and it has a broad-band line in the sub-band graph.
This by the way is a known pulsar!!!
This candidate looks to be a pretty promising pulsar. It has a nice peak in the pulse
profile, and is also narrow. In the time series graph, you can see the pulsar show up in
most of the observation. The S-Band graph shows the signal received showed up in all
frequencies, thus being broadband (the quality of pulsar). Finally the DM measure of this
candidate is pretty good, it has a nice symmetrical peak and is not far away.
This is the kind of plot that may contain a pulsar that hasn’t been discovered yet. The
peaks are high and although the vertical bands in the Sub-band graph are faint, they are
present. The DM is fine and the reduced chi squared is above one. The pulsar period is
also long enough for a person to think it was a pulsar and not noise.
Conclusion
Throughout the ten plots that we analyzed,
only three candidates were worthy enough
to be followed up, while the remaining
plots were RFI and/or noise. With this
information, we now have a better
understanding on how pulsars look on
plots and work.
Credits
Trent Jolin
Brianna McCourt
Jonathan Castillo
Staci Pritt
Jennifer Gore
Madonna Lott