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Constraining properties of dense matter with precision radio timing measurements Bennett Link

What spin variations have revealed about:
· the ground state of NS matter · its dynamics

Future directions (and wishes)


The central question of nuclear physics
What are the properties of matter above nuclear density (~ 3в1014 g cm-3)?

Such dense matter exists in neutron stars
M R

= M/(4R3/3) = 5x1014 g/cm3 2 nucleus.


The central question in neutron star physics
Atmosphere: H, He, C.... Crust: heavy elements Fe, Ni...

WHAT IS IN HERE?


The NS ground state (according to theory)

>n=2.8в1014 g cm-3
superfluid neutrons

Predictions:
Most of the interior is liquid, with SF neutrons + SC protons (type II)

?
Superconducting protons (type II) e-,

Questions:
Is this right? What are the implications?


Constraining the ground state of NS matter
Some NSs precess (nutate) with periods of years
PSR 1828-11
1 0 -1 1 0.5 0 49500 50000 Modified Julian date 50500 51000 ! p (ns) beam shape

(Stairs et al. 00)


Inconsistent with this theoretical prediction B
>n=2.8в1014 g cm-3
superfluid neutrons

Flux tube

?
Superconducting protons (type II) e-,

?
vortex

which would precess with a period of at most seconds, rather than years. (Link 03).

the current picture of ground state of the interior is seriously challenged


Constraining composition (equation of state)
EOS 1

P

EOS 2 EOS 3

Want M and R for the same object. Rapid rotators: fastest observed is 716 Hz. Discovery of a kHz pulsar would be very constraining.

LMXB

HMXB

~2 ! nuc

!

PSR+WD

PSR+NS


Constraining internal dynamics with spin variations
Glitches

loose (liquid) component

Statistically, Il

oose

I

1

%

suggestive of inner-crust origin
(Link, Epstein & Lattimer 99)


Constraining internal dynamics with timing noise


Evidence for a damped rotational mode

damped mode with ~ 10 d.

(Price, Link, Shore, Kramer & Lyne, in preparation)


Two pay-offs of precision pulsar timing
Discovery of precession
1 0 -1 1 0.5 0 49500 50000 Modified Julian date 50500 51000 ! p (ns)

challenges

superfluid neutrons

beam shape

?
SC protons (type II)

Discovery of correlated structure in timing noise

detection of crust-liquid dynamics?


Key ingredients for further progress
EOS: Need more masses SURVEYS!

Internal dynamics: Need frequent (daily) timing of choice pulsars to identify modes.