Hunting for Glitches

Sarah Buchner

• …are the leftover cores from supernova explosions. • Almost black holes• Neutron stars are very dense (1017 kg/m3 )

– 1.5 M with a diameter of 10 to 20 km

– Mass 1027 tons

• They rotate very rapidly: Period = 1.3 ms to 8 sec• magnetic fields are 1013 times stronger than Earth’s.

Neutron Stars

Chandra X-ray image of the neutron star left behind by a supernova observed in A.D. 386.The remnant is known as G11.20.3.

Pulsars and Neutron Stars

The Pulsar

Vela Pulsar

• PSR 0833-45• Vela supernova remnant• About 10 000 years old• P = 0.089 s = 11.2 Hz

• HartRAO observed • most days since 1984

Pulsars – stable clock• Massive stable flywheels superb cosmic clocks

e.g. Vela:

Unambiguously number each pulse

There were exactly 47 414 570 pulses between

11 Mar 2004 20:55:37and

29 Apr 2004 21:41:37

OH masers

Source below

horizon

VLBI

1s.Hz

-1310(6)-156.20475

Hz 00910.000000005181711.1910720

Phase residuals

Glitch Detection

• When phase offset > limit• Continual observing begins • Alarm at HartRAO• sms observers• Astronomical telegram / IAU circular

Spin-upnu

-5

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60 70 80 90

MJD 48437

nu

x 1

E6

610715.2

Recovery

-25

-20

-15

-10

-5

0

5

0 10 20 30 40 50 60 70 80 90

MJD 48437

nu

do

t

Recovery time scales0.4 and 4.1 days

Cause of glitch - starquake

R

R2

I

I

//=10=10––66

ε = 10= 10-4

//=10=10––66

ε = 10= 10-4

Vortex pinning and unpinning

Vortex pinning

Vortex current depends on lag

Glitch

SSCC II

Spin-upnu

-5

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60 70 80 90

MJD 48437

nu

x 1

E6

610715.2

Linear coupling “resistive”

Crust

Pinned superfluid

Next

Nint

Nint

coupleextcc NNI

)(I

N CSCcouple

)(I

NI CSCextCC

)(I

I CSCSS

Simple model

Spin-down

Non-linear coupling “capacitive”

Post-glitch recovery

n

t

n0)( ett pp

pd)( dtet

Recoveries have same form?

Predicting glitches

But …..

Do glitches occur randomly?

Size of angular momentumreservoir

Slope sets a lower limit to

IIres

Crab vs Vela

96 1010 910

How fast does the crust spin up?

Can we catch a glitch in the act?

XDMObservations

Timing Vela with XDM

Thanks

• HartRAO workshop staff and astronomers

• Adriaan Hough

• Richard Lord

• Simon Ratcliffe