The hard X-ray spectrum of
Pulsar Wind Nebulae
Data-models comparison in the Simbol-X era
F. Bocchino, INAF Osservatorio Astronomico di Palermo
with contributions of
R. Bandiera (INAF-OAA), L. Del Zanna (UNIFI), D. Volpi (UNIFI),
G. Cusumano (INAF-IASF Pa)
Introduction
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What is a PWN...
Introduction
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The mechanism which bring particles
and fields to the outer edge of the
nebulae is still under investigation
“It's like finding the transmission lines
between the power plant and the light
bulb.” (J. Hester, Arizona Univ.)
Examples of PWNe
1’
The Crab Nebula
 SN1054
 LX=2.4 1037 erg/s
 Distance 2 kpc
 Calib. source
Examples of PWNe
1’
The Vela PWN
 Age 11 kyr
 LX=6 1033 er
 D = 0.2 kpc
Symbol-X and PWNe
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Doing Chandra-like imaging is hopeless
Low bkg will make Symbol-X extremely competitive
w.r.t. current non-imaging hard X-ray instruments
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Easy detection of PWNe above 10 keV in reasonable singlepointing exposure time
Recent advances in theoretical modeling of PWNe
have pointed out the importance of the study of the
shape of PWN integrated X-ray spectrum
Spectra of PWNe
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Zero order approximation
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Synchrotron aging of a constantly injected
power-law population (Ginzburg &
Syrovatskii 1965)
Spectra of PWNe
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Modern approaches based on
inhomogeneous models
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MHD simulations, calculations of
synchrotron emissivities (Del Zanna et al.
2006)
Spectra of PWNe
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Alternative views
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Diffusive synchrotron radiation from PWNe
(Fleishman & Bietenholtz 2007)
Aimed to overcome
difficulties of “classical”
approaches to “non-Crab
like” PWNe
X-ray spectra of PWNe
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XMM-Newton 30 ks
INTEGRAL/IBIS, 439
SCWs in 2003-2004,
1 Ms
fX = 0.4 mCrab
Single power-law
NH=2.5+/-0.1 1022
cm-2
g = 1.74 +/- 0.06
Data sensitivity to spectral
breaks in hard X-ray
Data sensitivity to spectral
breaks in hard X-ray
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VELA: Mangano et al (2006),
BeppoSAX MECS+PDS
CRAB1: de Jager et al. (1996),
balloon-borne experiments
CRAB2: Massaro et al. (2000)
BeppoSAX NFI+HP+PDS
Data sensitivity to spectral
breaks in hard X-ray
Black: XMM 30 ks + ISGRI 1 Ms
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VELA: Mangano et al (2006),
BeppoSAX MECS+PDS
CRAB1: de Jager et al. (1996),
balloon-borne experiments
CRAB2: Massaro et al. (2000)
BeppoSAX NFI+HP+PDS
Data sensitivity to spectral
breaks in hard X-ray
Black: XMM 30 ks + ISGRI 1 Ms
RED: Suzaku 300 ks std. bkg
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VELA: Mangano et al (2006),
BeppoSAX MECS+PDS
CRAB1: de Jager et al. (1996),
balloon-borne experiments
CRAB2: Massaro et al. (2000)
BeppoSAX NFI+HP+PDS
Data sensitivity to spectral
breaks in hard X-ray
Black: XMM 30 ks + ISGRI 1 Ms
RED: Suzaku 300 ks std. Bkg
Green: Simbol-X 100 ks
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VELA: Mangano et al (2006),
BeppoSAX MECS+PDS
CRAB1: de Jager et al. (1996),
balloon-borne experiments
CRAB2: Massaro et al. (2000)
BeppoSAX NFI+HP+PDS
Data-model comparison in the
Simbol-X era
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Simulated synchrotron emission from
PWNe (Del Zanna et al. 2006)
run A: s=0.025, nearly ideal case for Crab
run B: s=0.1 large equatorial unmagnetized region
pole
equator
pole
Data-model comparison in the
Simbol-X era: the Crab
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Only the nebular
emission is
considered
VELA: Mangano et al 06 (obs)
CRAB1: de Jager et al. 1996
(obs)
CRAB2: Massaro et al 2000
(obs)
LDZ06: Del Zanna et al 2006
(models)
Data-model comparison in the
Simbol-X era: the Crab
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Black: Simbol-X 100 ks simulated spectrum
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Only the nebular
emission is
considered
VELA: Mangano et al 06 (obs)
CRAB1: de Jager et al. 1996
(obs)
CRAB2: Massaro et al 2000
(obs)
LDZ06: Del Zanna et al 2006
(model)
Data-model comparison in the
Simbol-X era: 3C 58
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Prototype of “non-Crab like” PWNe
Diffusive synchrotron radiation from
PWNe (Fleishmann & Bietenholtz 2007)
seems to overcome the difficulty of low
frequency and large change of slope of
the break in the radio band
What about in the X-ray band?
Data-model comparison in the
Simbol-X era: 3C 58
DSR 3c58: Diffusive
synchrotron radiation
model of Fleishmann
& Bietenholz (2007)
tailored to 3c58
broad band
spectrum
Data-model comparison in the
Simbol-X era: 3C 58
Black solid: XMM 30 ks
DSR 3c58: Diffusive
synchrotron radiation
model of Fleishmann
& Bietenholz (2007)
tailored to 3c58
broad band
spectrum
Data-model comparison in the
Simbol-X era: 3C 58
Black solid: XMM 30 ks
Red solid: Simbol-X 100 ks
DSR 3c58: Diffusive
synchrotron radiation
model of Fleishmann
& Bietenholz (2007)
tailored to 3c58
broad band
spectrum
Conclusions
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The shape of the hard X-ray spectrum of Pulsar Wind Nebulae is
directly related to the distribution of B and e- in the source
Current measurements are just enough to provide some diagnostics
for the brightest objects (Crab and Vela)
Simbol-X may provide an order of magnitude improvement in the
comparison between model and observations for these bright sources
Other bright PWNe (G21.5-0.9, 3C58) are hardly detected by nonimaging hard X-ray instruments. Simbol-X will provide THE unique
opportunity to study the spectrum above 5-10 keV.