neutron stars glitches - mcgill...
TRANSCRIPT
Neutron Stars GlitchesEmilie Parent
EPSC 510 Presentation
November 10th
Outline
1. What is a neutron star2. Observations of neutron stars3. Interior of neutron stars4. Glitches
1. What is a neutron star
1. What is a neutron star
Forms when a massive star dies in a supernova explosion
1. What is a neutron starSupernova remnants seen by NASA’s telescopes
1. What is a neutron starSupernova remnants seen by NASA’s telescopes
Enormous amount of energy released The core collapses Neutron star is born
Energy stored in angular momentum
1. What is a neutron star
A neutron star is ..
VERY hotVERY denseVERY magnetized VERY stable rotationally
..and VERY cool
2. Observations of Neutron Stars
2. Observations of Neutron Stars
A Pulsar is ..
A rotating neutron star emitting beams of radiation A cosmic lighthouse
..and VERY cool
As the star rotates, we receive a periodic signal.
The beams can be x-rays from a hot spot a the surface, or radio light emitted at the magnetic caps of the neutron star,
2. Observations of Neutron Stars
2. Observations of Neutron Stars
Radio pulsars : Need a misalignment of the magnetic axis with respect to rotation axis to be able to detect it
2. Observations of Neutron Stars
Toys to observe radio pulsars
Big toys to observe radio pulsars2. Observations of Neutron Stars
As the star rotates, we receive a periodic signal from the it.
The beams can be radio light emitted at the magnetic caps of the neutron star, or x-rays from a hot spot a the surface
2. Observations of Neutron Stars
2. Observations of Neutron Stars
Extremely precise clocks
Spins down due to dipole radiation (plus GW, plus cooling, plus wind, sometimes)
218.8118438547254 ±0.0000000000009 Hz
3. Interior of Neutron Stars
3. Interior of Neutron Stars
Nuclear saturation
Fermi energy dominates over thermal energy: behaves as a cool body
3. Interior of Neutron Stars
Structure
Atmosphere : ~0.000001 m thick
Crust: 1-2 km thickCrystalline lattice of ions, which a sea of free electrons and neutronsElastic solidSuper duper smoothRotation can reach few % of the speed of light
3. Interior of Neutron Stars
Structure
Inner-crust / outer core :Density increases, more and more neutronsZero viscosityPasta phase
3. Interior of Neutron Stars
Pasta phase : Nuclei are no longer spherical
3. Interior of Neutron Stars
Outer core: superfluid of neutronsInner core : superconductor ?
3. Interior of Neutron Stars
Outer core: superfluid of neutronsInner core : superconductor ? Take away point:
We don’t know the equation of state of neutron star's interior.
We can’t reproduce these extreme environments in
laboratories
4. Glitches
4. Glitches
Sudden increase in spin frequency
Changes in frequency of the order of 10-5 to 10-12
~10% of observed pulsars have glitch every few years
L.M. Gonzalez-Romero, J.L. Blazquez-Salcedo 2009
4. Glitches
Sudden increase in spin frequency
Changes in frequency of the order of 10-5 to 10-12
~10% of observed pulsars have glitch every few years
4. Glitches
2 proposed models for glitches:
1. Star Quakes
2. Unpinned vortices
4. Glitches Model 1 : Star Quakes
Gravity wants the star to be spherical
Fast rotation of elastic crust makes the star oblate
4. Glitches Model 1 : Star Quakes
Stress builds up on the crust as the star spins down.Reaches eventually critical strain : need to readjust its
shape
4. Glitches Model 1 : Star Quakes
L = ѡ x I : if I goes down suddenly, ѡ goes up, hence the glitch
4. Glitches Model 1 : Star Quakes
Haskell & Melatos 2015
Oblateness
Total Energy, must be minimized while keeping L constant
Stress released in a crust quake
Waiting time until the next glitch
4. Glitches Model 1 : Star QuakesObservation : Vela pulsar
Chandra + HST
4. Glitches
2 proposed models for glitches:
1. Star Quakes
2. Unpinned vortices
Model 2 : Unpinned Vortices4. Glitches
Superfluid is irrotational
Boson condensate → quantum vortices
Quantum vortices carry quantized angular momentum
Model 2 : Unpinned Vortices4. Glitches
In superfluid, can change configuration of vortices and make vortices disappear
When nuclei are arounds, can’t reconfigure easily : vortices are pinned to nuclei
Glitch video
Summary
1. Figuring out the state of the matter in the interior of neutron stars is still a huge challenge
2. Pulsars glitch, and we are still not sure how this is happening
3. One of the model for glitches is crust quakes, but this model fails badly to explain some observations
ReferencesAndreas Reisenegger 2013, Magnetic fields of neutron stars , ApJ
http://www.cv.nrao.edu/course/astr534/PulsarTiming.html
Brynmor Haskell & Andrew Melatos, 2015 Models of Pulsar Glitches, ApJ
Vanessa Graber, Nils Andersson, Michael Hogg, 2016, Neutron Stars in the Laboratory, arXiv:1610.06882
Lorimer and Kramer, 2005, Handbook of pulsar astronomy, Cambridge University Press
William G. Newton, 2013, A Taste of Pasta?, Nature arXiv:0912.0628v1 [gr-qc] 3 Dec 2009L. M. Gonz ́alez-Romero and J. L. Bl ́azquez-Salcedo, 2009, Core-crust transition pressure evolution in post-glitch epoch for a Vela-type pulsar, arxiv.org/abs/0912.0628
http://chandra.harvard.edu
C. Reichhardt, 2001, Commensurate and Incommensurate Vortex Lattice Melting in Periodic Pinning Arrays, Physical Review B 64, 144509
3. Interior of Neutron Stars
Outer core: superfluid of neutronsInner core : superconductor ? What we need to pin down
EOS?:
More exotic pulsars (in terms of mass and/or binary system), or to see pulsars doing crazy
things
2. Observations of Neutron Stars
Pulsar timing: predicting the time of arrival of pulses
time
Period
2. Observations of Neutron Stars
Pulsar timing: predicting the time of arrival of pulses
time
Period
2. Observations of Neutron Stars
Pulsar timing:
Use phase coherence instead
Observe pulsar at regular interval
Measure precisely at what time the pulses arrive
Model arrival times of future pulses
Need to barycenter the data