Pulsar Wind Nebulae with LOFAR

Jason Hessels

(ASTRON/UvA) QuickTime™ en een TIFF (ongecomprimeerd)-decompressor zijn vereist om deze afbeelding weer te geven.

QuickTi 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. 16 th -19 th , 2008

Outline

Observing Pulsar Wind Nebulae (PWNe) with LOFAR 

General theoretical model of PWNe

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Observational properties of PWNe

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Observing PWNe with LOFAR

Astrophysics with E-LOFAR - Hamburg - Sept. 16 th -19 th , 2008

Pulsar Wind Nebulae (PWNe):

a.k.a. “Plerions” < 10% of “spin-down” energy converted into pulsations QuickTime™ and a YUV420 codec decompressor are needed to see this picture.

Chandra time-lapse view of Crab PWN Majority is released as a pulsar wind 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, 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 Crab Nebula From Gaensler & Slane (2006) 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

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 resolve nebula) (can  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 QuickTime™ en een TIFF (ongecomprimeerd)-decompressor zijn vereist om deze afbeelding weer te geven.

G11.2-0.3 Roberts et al. 2002 Roughly half of the ~50 known PWNe are “naked” 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 (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 self absorbed?) PWNe will be dim, LOFAR’s huge collecting area will be critical

Soft X-ray Hard X-ray Radio

PWN with LOFAR

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.

Larger/smaller extent at low freq.?

PWN with LOFAR

Spatially Resolved Spectroscopy and Polarimetry Direction of proper motion and spin axis Electron cooling as one moves away from pulsar 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

LSI +61 o 303 Dhawan et al. 2006 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) Be-star companions (PSR B1259-63, LSI +61 o 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 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. 16 th -19 th , 2008