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Neutron Stars

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Sabrina Berger

on 25 October 2014

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Transcript of Neutron Stars

Or... How can we describe the force between protons and neutrons in all cases?
We are adequately familar with the forces between quarks. The so called
Simplistically, there are
3 quarks per baryon,
Understanding the
Strong Force through
A black hole is supposed to be the densest object in the universe...
What is the strong force?
and output
energy density
Observations of neutron stars
Nuclear saturation density = 2.5 * 10^14 g cm^-3
n0 ~ .016/fm^3
So at the core of a neutron star, matter is even
more dense than that in a nucleus!
Are glitches the
to understanding
A glitch is a rare occurrence in a pulsar when a sudden increase in frequency and decrease in period are detected.
The second densest object in our universe is a neutron star.
A neutron star is a stellar remnant of a
star with an inital mass between 8-30 solar masses
core collapse supernova at the end of its nuclear fusion life
THE SMALLEST with radii estimated around 10 - 20 km ASK
What is a neutron star?
The residual,
force is what extends from the nucleons and binds them together.
from ~ 10^6 (outer crust) to 10^15 g cm^-3 (core)
How dense is neutron star matter?
They have been deemed many times as the clocks of the universe.
Neutron stars are
stellar remants denser than an atomic nucleus at their cores.
What is an equation of state (EoS)?
Diameter: 20-30 km
x 7 billion
Neutron Star Structure
Why do pulsars glitch?
The two-component model for glitches describes the pulsar as having two distinct components rotating at different rates.
Superfluidity in Helium-3
2) The faster moving component of the star that transfers its angular momentum to 1.
1) The charged component of the star that includes:
outer crust
inner crust lattice of exotic nuclei
core protons
electrons in the star
the neutron superfluid that is spun up in the core by the glitch
The Two Components
is at least 1.6% from observations in the Vela pulsar.
P as a function of density, temperature and proton fraction
When the Magnus force overcomes the pinning force on the neutron superfluid in the inner crust, a glitch will occur.
What is the neutron star EoS?
The Skyrme interaction
models the potential energy between neutrons and protons but still has many unknown constants.
Input EoS into the Tolman-Oppenheimer-Volkoff (TOV) Equation
Tolman-Oppenheimer-Volkoff (TOV) Equation
Properties of Neutron Stars
Nuclear Symmetry Energy
and its slope L
Strong Crustal vs. Crustal Neutrons
REU 2014
By Sabrina Berger
When will a glitch occur?
Strong crustal vs. crustal neutrons
The amount of neutron superfluid in the core actually increasing in its rotational velocity during the glitch.
Vela Pulsar - Credit of NASA/CXC/PSU/G.Pavlov et al.
Today's Presentation
Pulsars and glitches
Our model for glitches
Constraining Yglitch (neutrons coupled during glitch/total star) with mutual friction
Now we can talk about the research.

Δf = (frequency of faster component) − (frequency of slower component) is proportional to the strength of Magnus force.
The Model
So then we can say...
Dense matter
found in neutron stars is a supreme laboratory
Empirical data from
restrict the physics of the two-component model
two-component model
could lead to conclusions about the
neutron star EoS

Shows the strong pinning region shaded as grey- Credit: Hooker, Newton, Li 2014)
Credit: Learn EveryWare, © 2009 Alberta Education and Ethan Siegal
Credit: Daniel Smith/FOX
Credit: Discovery, DAVID TEEGHMAN
Credit: NASA/SDO
Credit: Kantilal Patel
Credit: BBC
Credit: DeadRinga on Pichost
Credit: NASA Scientific Visualization Studio
Credit: Andrew G. Lyne and Francis Graham-Smith in
Pulsar Astronomy
Credit: Apple
Credit: University of London
Credit: UMD
L is between 25 and 115 MeV.
Credit: Vasudevan Mukunth
Credit: J. Hooker, W. G. Newton and Bao-An Li

Mutual friction (B) could help us determine the Yg ratio.
Yg = coupled portion/total star

Yg is the ratio of neutron superfluid in the core that gets spun up at all during the glitch.
can be calculated from the time a glitch takes to spin up the star.
Mutual friction?
Determining Yg may be possible with better measurements of
mutual friction
could lead us to a more accurate EoS for extremely dense matter
From this EoS we could understand the
strong force

The Skyrme interaction models the strong force.
Mentor: Dr. William Newton
Calculating G with mutual friction
Calculating Yg with mutual friction
Activity Parameter of the
Vela Pulsar
For the first time, using observational data from the glitch recovery time, we have been able to constrain Yg (neutrons coupled during glitch/total star).
Modeling the glitch using the two component model with realistic equations of state, we do not reproduce the observed glitch activity of the Vela pulsar.
of the glitch model?
of the equation of state

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