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

Topic 1:

X-ray diagnosticsfor acc. efficiency of electrons

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!

Topic 2:

X-ray diagnosticsfor acc. possibility of protons

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 !

Topic 3:

X-ray diagnosticsfor acc. efficiency of protons

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/