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Dakota Johnson, Tildon Johnson, Kyle Barker
Rowan County Senior High School
Mentor: Mrs. Jennifer Carter
Abstract
Pulsars are rapidly rotating neutron stars that have extremely large mass and
magnetic fields, and spin precisely in time. Gravitational waves, proposed
by Einstein, are thought to be created when large mass objects accelerate.
Pulsar astronomers need additional observations of millisecond pulsars for
the NANOGrav program that uses precise periods to detect these
gravitational waves. A group of pulsar astronomers established a program
for high school students called the Pulsar Search Collaboratory (PSC) to use
over 30 terabytes of data collected by the Green Bank Telescope (GBT). The
data that was collected by the GBT was reduced by using a Fast Fourier
Transform algorithm that generated the plots analyzed. During the analysis,
pulsar J2048-1616 was rediscovered. The data collected from this pulsar
will add to the knowledge of pulsars as a whole despite not being not useful
in gravitational wave detection due to the pulsar not being a millisecond
pulsar.
Radio Frequency Interference
Approximately 17% of RFI analyzed was emitted from power lines at
frequencies of 60 Hz and its harmonics. The remaining RFI was emitted
from unknown sources. See Figure 3.
J2048-1616 Spin Down
The spin down rate of pulsar J2048-1616 is calculated using the
period and Mean Julian dates from the PSC database and the
Australian National Telescope Facility catalogue.
Introduction
A pulsar is a highly magnetized neutron star that emits radiation as beams
from its magnetic field poles. To observe these types of neutron star, the
beam from it must be pointed towards the Earth. Imagine a lighthouse and
its rotating beams of light that stem from it. This examples helps
demonstrate how you see the light when it is pointing towards you. Pulsars,
like all neutron stars, are very dense and they have very precise periods (the
time it takes to complete a spin).
Figure 3. The amount of RFI that came from power lines.
While the Green Bank Telescope was being repaired in 2007, three
astronomers (Dr. Duncan Lorimer, Dr. Maura McLaughlin, and Sue Ann
Heatherly) turned on the telescope as it was immobile and recorded data as
the Earth rotated. Once completed, they had recorded more than 300
observing hours and over 30 terabytes of data. They realized that they could
not analyze all of this data by themselves, so they decided to write a grant to
organize the PSC program to train teachers and students to analyze the data
sets.
Charactersistic Age of J2048-1616
A pulsar’s characteristic age is an estimate of how long it has been since the
pulsar was born in a supernova explosion. The characteristic age is
calculated by using the pulsar’s period and period derivative. The
characteristic age only applies on pulsars that have not re-accelerated from
accreting the mass of a companion star. The characteristic age is calculated
below:
Approach
The research that was conducted was done by analyzing over 1000 plots of
data from the Pulsar Search Collaboratory and identifying them as radio
frequency interference, noise, a new pulsar, or a pulsar that had already been
discovered. Noise is the discrete signal that the telescope observes.
Everything in the universe gives off electromagnetic radiation and it gets
collected as the telescope is collecting its data. Radio frequency interference
(RFI) is a strong and deceiving signal that may come from space or the
Earth. Commonly, RFI is emitted from man-made sources, such as power
lines, satellites, etc.
Data Analysis
Figure 4. The spin down rate of J2048-1616. The slope of the line is
the p-dot. The positive slope indicates the period is increasing with
time and is therefore spinning down, as it is expected. As pulsars
age, the period usually decreases due to magnetic braking from the
emission of magnetic dipole radiation. Binary systems are
exceptions as the characteristic age equation only applies to isolated
pulsars that have not been spun up by a companion.
Period – 1.96179738255 s
P-dot – 2.2331 × 10−11 𝑠/𝑠
Image 1. A standard RFI plot. This plot is particularly interesting because of
the strong signal that appears sporadic and exceeds the data range of the
table. The cause of the phenomenon is a very strong signal from something
𝜏 = 4.208059594 × 1010
The characteristic age is 1334.36 years old.
Pulsar J2048-1616
Pulsar J2048-1616 was discovered by A.J. Turtle and A.E. Vaughan in the
southern hemisphere in 1968. At the time of its discovery, this pulsar had
the longest announced period yet, 1.961 seconds.
Figure 1. The location of the pointings of the data analyzed. This graph
displays the Right Ascension and Declination of the plots analyzed:
The most common area of Declination was -15:00.
There was an almost constant Declination during the time that this pointing
took place. The Green Bank Telescope was unable to steer, indicating that it
was at immobile declination. As the Earth turned, a range of Right Ascension
was observed while not changing the Declination more than a few degrees at
a time.
J2048-1616
The distinct signal in the pulse profile and the vertical broadband emission
(due to the pulsar emitting electromagnetic radiation in all spectrums)
shown on the sub-band plot indicate that this plot is potentially a pulsar.
The dispersion measure (DM) is very peaked and that is a characteristic of
this subplot that we want in a pulsar. The fact that it is not peaked at zero
indicates it is not located near the surface of the Earth.. Manmade signals
that are emitted from near the Earth have dispersion measures at or near
zero.
Image 3. The P-Pdot diagram. The P-Pdot diagram displays the pulsar’s estimated
age by using the age of other pulsars, the period of your pulsar, and the period
derivative of your pulsar. Plotting pulsar J2048-1616 on the P-Pdot diagram
provides an approximation of the magnetic field strength and energy loss.
Acknowledgements
Figure 2. The identification of the data analyzed. This chart displays the
different categories of identification of data. They were either noise, RFI, or
a known pulsar. Only one known pulsar was identified.
Image 2. The PSC plot of the known pulsar, J2048-1616.
A special thank you goes out to:
Jennifer Carter
All PSC Astronomers
Pulsar Search Collaboratory staff