Pulsar Wind
Nebulae with
LOFAR
QuickTime™ en een
TIFF (ongecomprimeerd)-decompressor
zijn vereist om deze afbeelding weer te geven.
Jason Hessels
(ASTRON/UvA)
Quic k Ti me™ en een
T IFF (ongec om pri meerd)-dec ompres s or
zi jn vereis t om deze afbeel ding weer t e geven.
Astrophysics with E-LOFAR - Hamburg - Sept. 16th -19th, 2008
Outline
Observing Pulsar Wind Nebulae (PWNe)
with LOFAR
 General theoretical model of PWNe
 Observational properties of PWNe
 Observing PWNe with LOFAR
Astrophysics with E-LOFAR - Hamburg - Sept. 16th -19th, 2008
Pulsar Wind Nebulae (PWNe):
a.k.a. “Plerions”
< 10% of “spin-down” energy converted into
pulsations
Majority is released as a pulsar wind
QuickTime™ and a
YUV420 codec decompressor
are needed to see this picture.
The wind continuously injects high-energy
electrons/positrons and magnetic
field at the centre of an expanding supernova
remnant producing a synchrotron nebula
In general, PWNe are found around the
youngest and/or most energetic pulsars,
Chandra time-lapse
view of Crab PWN
Wind persists beyond point where nebula is
visible
Not just young pulsars: also high Edot, or
strong wind confinement (high-velocity
pulsars)
~ 50 PWNe known
•
Schematic PWN
(young pulsar case)
PWN: Synchrotron-emitting
bubble of energetic particles
at the center of an expanding
supernova remnant
Wind is not isotropic:
equatorial and polar outflows
Crab is in many ways the
prototype
Also bow-shock nebulae
(high-velocity pulsars) and
wind shocks in compact
binaries
From Gaensler & Slane (2006)
Observational Characteristics
Most PWNe only observed
at cm radio and 1-10 keV
X-rays
Decreasing size of nebula
going from radio to X-rays
General radio properties:
- radio-emitting e-/e+ have very
- long synchrotron lifetimes
- amorphous (not shell-like or torii)
- filaments and other structures
- high (>10%) fractional linear
- polarization
- flat, non-thermal, power-law
- spectrum (alpha = 0.0-0.3)
- need for spectral break between
- radio and X-rays
-
Crab Nebula
From Gaensler & Slane (2006)
Astrophysics of PWNe
 Pulsar birth properties (link to
progenitor properties?)
 Understanding the P-Pdot diagram
(i.e. pulsar energetics and magnetic
fields)
 Relativistic flows/shocks (can
resolve nebula)
 Particle acceleration and
interaction with ISM
 Strong link with Galactic
population of rare GeV and TeV
sources
PWN with LOFAR
Detect SNR shells around known PWNe
Roughly half of the ~50
known PWNe are “naked”
QuickTime™ en een
TIFF (ongecomprimeerd)-decompressor
zijn vereist om deze afbeelding weer te geven.
e.g. the elusive Crab SNR
shell (crab supernova blast wave
hasn’t interacted with enough
surrounding gas yet?)
Provide information on the
composition and density
profile of the material that
the nebula is expanding into
G11.2-0.3
Roberts et al. 2002
(relation between environment and
morphology)
-
PWN with LOFAR
Where does the radio spectrum turn over?
LOFAR
Flat spectrum in the
radio with one or
several spectral breaks
necessary to connect
with the X-rays
At what low freq does
this turn over? (does
emission become selfabsorbed?)
PWNe will be dim,
LOFAR’s huge
collecting area will be
critical
PWN with LOFAR
Soft X-ray
Hard X-ray
Radio
Morphology and Extent
Radio-emitting electrons
have very long synchrotron
lifetimes, trace energetic
history of the pulsar
Radio filaments and other
features marking regions of
instability
LOFAR (long baselines incl.)
will have similar (arcsecond)
resolution to Chandra
Compare X-ray/radio morph.
G0.9+0.1
G11.2-0.3
Dubner et
et al.
al. 2003
2008
Roberts
Larger/smaller extent at low
freq.?
PWN with LOFAR
Spatially Resolved Spectroscopy and Polarimetry
Electron cooling as one moves
away from pulsar
Direction of proper motion
and spin axis
Spectral steepening observed
in X-rays (also in radio?)
Polarimetry (not yet possible
in X-rays) to trace magnetic
structure far out in the nebula
Relate to pulsar geometry and
proper motion
Vela - Dodson et al. 2003
PWN with LOFAR
Pulsar Winds in Binary Systems
Pulsar wind can be strongly
confined near the pulsar
Probe the wind at very small
distance from the pulsar
Double pulsar PSR J0737-3039
(within light cylinder)
Black-widow pulsars (PSR
B1957+20)
+61o 303
LSI
Dhawan et al. 2006
Be-star companions (PSR
B1259-63, LSI +61o 303?)
PWN with LOFAR
Target Galactic TeV sources
The TeV Sky in 2008
figures courtesy Jim Hinton
VERITAS (“northern HESS”) also coming online
Summary
PWN observations with LOFAR
QuickTime™ en een
TIFF (ongecomprimeerd)-decompressor
zijn vereist om deze afbeelding weer te geven.
Find SNR shells around “naked” PWNe
Map low-frequency spectrum and cut-off
Morphology and extent
Spatially resolved spectroscopy and polarimetry
Find new PWNe in binary systems or associated
with Galactic TeV sources
Astrophysics with E-LOFAR - Hamburg - Sept. 16th -19th, 2008