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transcript
Observational evidences ofparticle acceleration at SNRs
Aya Bamba (RIKEN, Japan)and Suzaku team
SuzakuChandra
1.X-ray observation for cosmic-ray study
2.topic 1:X-ray study on acceleration
efficiency of electrons3.topic 2:
X-ray study on acceleration possibility of protons
4.topic 3:X-ray study on acceleration
efficiency of protons5.Summary
0. Talk plan:
1.1. how to search accelerators?
Koyama et al.(1995) Discovery of sync. X-rays from the shell of SN 1006 SN1006:
type Ia d=2.18kpc
10´
Shocks of SNRs = cosmic ray accelerators!
…. but details are unsolved
TeV electronIS B (~G)
sync. emission in hard X-raysX-rays are the best indicator
gyro radius of TeV e = a few pc
1.2. Remaining problems
acc. efficiencyof electrons
acc. possibilityof protons
acc. efficiencyof protons
distribution ofsynch. X-rays
(Chandra)-> topic 1
For all of these remaining problems,X-rays are the strong tool !
wide-band spectra(radio - TeV)
(Suzaku)-> topic 2
plasma diagnosticsin X-rays(Suzaku)
-> topic 3
1.3. X-ray satellites
spatialresolution
effectivearea
energy range
spectral resolutionfor diffuse sources
Chandra
Suzaku
XMM-Newton
Each satellite hasstrong points
2.1. observational information to solve
The spatial distributiontheir gyro radius, the turbulence of B, ….
The spectrum of synchrotron emissionthe maximum energy, B, ….
The age of the systemthe evolution of acceleration
Spatial resolution!
Chandra has excellent spatial resolution (0”.5)best for such a study
2.2. In the case of SN 1006Mei-Getsu-Ki (The diary of Teika Fujiwara)
ancient samples of guest
starsGreat guest
star like Marson 1006. May
1st
Crab nebula
3C58
Happy Birthday!
2.3. SN 1006 image
0.3 – 2.0 keV2.0 – 10.0 keV
downstream
upstream
SN1006 NE shell
(Bamba et al. 2003)
Energy (keV)1 50.3
thermal (0.24 keV)extended
non-thermalsharp
Scale length of the filaments?
us = 2890km/s
2.4. Fitting results
Mean value……………….Minimum value…………
wd
0.2 pc0.05 pc
wu
0.05 pc0.01 pc
10´´ = 0.1 pc2 – 10 keV
First measurement of the width of filaments
HardNo line
Non-thermal!
spectrum
0.5 1 5 10
= 0.57 @1GHz (fixed) (Allen et al. 2001)rolloff = 2.6 (1.9 – 3.3) x 1017 HzFlux = 1.8 x10-12 ergs cm-2s-1
(keV)
Reynolds & Keohane (1999)rolloff = 5x1017Hz B
10GEmax
100TeV
2
power-lawexponential cutoff
SRCUT model
2.5. Spectral Fitting
Sync. emission from electrons
SRCUT model
E
N(E
)Spectrum of electrons
Emax
em
issio
n
Synchrotron emissionfrom a single e
em
issio
nrolloff ~ Emax
2B
-12
Synchrotron emissionfrom power-law electrons
exp.
EmaxB
Cas A(SN1680)
Kepler(SN1604) Tycho(SN1572)
SN1006
RCW 86(SN184)
2.6. Many young historical SNRs have thin filaments with sync. X-rays
(Bamba et al.2005)
thin filaments are commonin young SNRs
2.7. Why are filaments so thin?….. Small diffusion in direction to shock normal!
shockup downEmax of electron 30-40 TeV
The angle: > 85 deg.The strength: 10 – 80 G
ordered or turbulent B ?
perpendicular B or parallel B ?
perpendicular!
turbulent → strongly scattered → hardly go downstream → staying long around shocks
turbulent Bhigh effic.
(equipartition)
Diffusion only occurs along the B
First quantitative image !
B ~ 100 – 400 G
very strongparallel B (Berezhko et al. 2004)
shock
up down
Anyway, Turbulent magnetic field (Bohm limit)Very efficient acceleration (equipartition)
another scenario
Strong B makes the gyro radius small → diffusion becomes small
First estimation of magnetic field structure
2.8. Time evolution of B
wd ~ rgus-1
~ EmaxBd-1us
-1
rolloff ~ Emax2Bd
B = rolloffwd-2 ~
Bd3us
2
Direct estimations of the evolution of BONLY from the observational facts!
us ~ t-0.6 (Sedov)
observational facts func. of Bd
tage (years) 200 500 1000 2000
B =
ro
lloff/w
d2 (
Hz/
pc
2)
10
17 10
18 1
019 10
20 10
21 10
22
rolloff/wd2 ~ tage
-2.96
Bd ~ tage-0.6 (Sedov)
+0.11-0.06
(2/d.o.f.=2.0/3)
(Bd
3u
s2)
(Bamba et al. 2005)
2.9. Time evolution of energy densitiesthermal uth: ~ T ~ tage
-1.2
kinetic ukin: ~ us2 ~ tage
-1.2
Magnetic energy density uB: ~ Bd2 ~ tage
-1.2
CR energy density uCR:
uA = B4 (Lucek & Bell 2000)
uB = uCR
uA
us
uCR ~ Bdus ~ tage-1.2
All energy densities have same time dependence!acc. efficiency for electron is very high!
Sedov
Our result (Bd ~ tage-0.6)
assumption:
Shock energy densitythermalkinetic
mag. energy density CR energy density
Non-linearEffect
shock evolutionIn mag. field
interaction ofmag. Field and CR
strong interaction for each otherIn each filament: equipartition
evolution keeping equipartition?
2.10. Images
We must consider these three energy density simultaneously!
3.1. How to search proton accelerators ?
The efficiency of electron acceleration is so high.however …
How about protons ?
electrons-> synch. X-rays + IC -raysprotons -> -rays via 0 decay
searching for X-ray dim & -ray bright sourcesTeV & X-ray observations are strong tool!
To find out proton accelerators …Energy
E2 dF
/DE
X-rays -rays
sync.
IC
0
HESS: TeV -ray telescope @ Namibia Imaging Atmospheric Cherenkov Telescopes since 2004
They have done Galactic Plane surveyfor the first time.
http://www.mpi-hd.mpg.de/hfm/HESS/HESS.html
3.2. TeV gamma-ray observations
Sgr A*
RX J1713
HESS J1837-069
HESS J1834-087HESS J1825-137
HESS J1813-178
HESS J1804-216
HESS J1640-465HESS J1614-518
HESS J1616-508
Aharonian et al. 2005
They have no counterpart.New accelerator candidates?
3.3. A candidate of p accelerators ? … HESS unIDs
along Galactic planediffuse sources
-> Galactic ?
-> X-ray follow-up is needed !
Their nature is unknown <- lack of counterparts
With deep absorption on Galactic plane,follow-up obs. are very difficult.
3.4. Introduction of Suzaku
The 5th Japanese X-ray satellite.
It was launched on July 10th 2005.
Suzaku is “Red Phoenix”, the protector God of the South.
The wall painting of Suzaku in “Kitora” tomb
朱雀 (Suzaku)
3.5. Instruments
XRT (X-Ray Telescope)Large effective area
450cm2 @1.5keV
XIS (X-ray Imaging Spectrometer)Improved X-ray CCD with high efficiency
and good energy resolutionLow BackgroundEnergy band : 0.2-12keV
HXD (Hard X-ray Detector)Wide energy band Si-PIN (10-70keV) & Scintillator (30-600keV)Non-imaging detector, but low background
XRT
XIS
HXD
Suzaku is bestfor follow-up of TeV unIDs !
young SNRs
old SNRs
large shock speedboth e and p are acceleratedstrong synchrotron X-rays
small shock speedelectrons are decceleratedno emission
SNRs colliding with MCs
amount of targetsstrong 0 decay
3.7. One possible scenario for TeV unID sources:Emission from SNRs in various phases
(Yamazaki et al. astro-ph/0601704)
TeV unIDs are old SNRscolliding with MCs?
Their nature is still unknown,but Suzaku will solve it !
kinetic Eof shocks
thermal Eof downstream plasma
kinetic Eof shocks
thermal Eof downstream plasma
E ofaccelerated particles
kinetic Eof shocks
Thin thermal plasma (~keV) emits linesin the X-ray band.
X-ray plasma diagnosticscan determine precise plasma parameters.
Suzaku XIS has good spectral resolution-> best for the study !
4.1. how to measure acc. efficiency of protons ?
from Rankine-Hugoniot relation
kTd = mvs22(-1)
(+1)2
~ 0.19 Eshock (no acc.) < 0.19 Eshock (efficient acc.)
5. Summary
1.We detected sync. X-rays from filaments in young SNRs.
2.The filaments are very thin !3.Thin filaments reveal us that the acc. efficiency of e
lectrons is very high.4.Suzaku deep observations reveal us that HESS unI
D sources might be proton accelerators.5.They might be old SNRs ?6.Suzaku will enable us to estimate the acc. efficienc
y of protons.
Notice ! Suzaku is providing a lot of fruitful data, andmany results of Suzaku observation are reported !
We will hold the conference “The Extreme Universe in the Suzaku Era” at Kyoto on December 4-8, 2006 !
Topics are not only SNRsbut all high E topics.
We are looking forward to your participating !!
http://www-cr.scphys.kyoto-u.ac.jp/conference/suzaku2006/