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Variability in

J0738-4042

Paul Brook

Aris Karastergiou, Steve Roberts, Sarah Buchner

University of Oxford

22th October, 2012

Formation & Evolution of Neutron Stars, Bonn

PSR J0738-4042

Seemingly average, middle-aged

pulsar

Period = 0.375 s

Period derivative = 1.6 x 10-15 s-2

Distance = 11.03 kpc

DM = 160.8 cm-3 pc

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credit: Handbook of Pulsar Astronomy (Lorimer & Kramer)

Profile Changes in J0738

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credit: Karastergiou et al., 2011

Profile Changes in J0738

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2004

2010

2006

credit: Karastergiou et al., 2011

Profile Changes in J0738

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credit: Karastergiou et al., 2011

2004

2010

2006

credit: Karastergiou et al., 2011

Simulations

Profile Changes in J0738

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credit: Karmesaroff et al., 1970

credit: Van Ommen et al., 1979 & 1990

credit: Karastergiou et al., 2011

Profile Residuals

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Profile Residuals

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Profile Residuals

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J0738 Timing Variations

HartRAO timing

data

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J0738 Timing Variations

2006

HartRAO timing

data

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J0738 Timing Variations

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credit: Steve Roberts

MJD

J0738 Modes

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Phas

e B

in

MJD

HartRAO Data, 1988 - 2008

56

00

0

Parkes, 2008 -

2012

Interpretation

? A sudden ‘event’ seems to occur

in the magnetosphere of J0738-

4042, seen in profile and

spindown rate changes.

A reconfiguration of

magnetospheric current seems to

take place over the next 150 days

until the profile and spindown

rate find stability

Could an external object be the

cause of a change in

magnetospheric current? (Cordes

& Shannon, 2008)

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More like J0738-4042?

We recently analysed

profiles of 180 pulsars using

data from Parkes

Preliminary work shows a

handful of pulsars with

possible profile variability

Timing data is next to be

analysed in order to find any

correlation with emission

variability

Already one stand-out

candidate…

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More like J0738-4042?

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More like J0738-4042?

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In Summary

A comprehensive understanding of emission and timing variability in pulsars

brings us closer to things such as the detection of gravitational radiation

J0738-4042 is highly unusual, and can teach us about the links between

timing and profile variability

It displays emission changes that are sometimes accompanied and sometimes

unaccompanied by changes in spindown rate

We can also hope to learn about what’s physical happening in / on these

objects to give rise to such variability

Could an asteroid be the trigger for dramatic changes?

Finding more examples of this type of pulsar variability will provide answers

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