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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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