X-Ray Measurements of Cosmic-Ray
Accelera9on Eﬃciencies in Supernova
Remnants

Satoru Katsuda (Saitama University)

2017/12/18

CTA Workshop @ U. Tokyo

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Cosmic Rays (CRs)
Cosmic rays were discovered by a balloon
experiment led by V. Hess in 1912.

Galac9c

1/m2/yr

Extragalac9c

Limit of groundaccelerator

1/km2/yr

Gaisser (2006)
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CTA Workshop @ U. Tokyo

A long-standing ques9on
connected to astrophysics:
Where are CRs accelerated?

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Supernova Remnants:
Promising Origin of Galac9c CRs1) Energy per unit 9me to maintain Galac9c CRs:
LGCR = 1040-41 erg/s = UGCR ~ 1055 erg / τ ~ 107 yr2) Energy per unit 9me given by supernova explosions:
LSN = 1042 erg/s = ESN ~ 1051 erg * RSN ~ 1/30 yr-1
à The energy budget can be balanced, if 10% of SN explosion energy goes
into CR accelera9on: LGCR/LSN ~ 0.1 (e.g., Baade & Zwicky 1934).
Moun9ng evidence for SNRs being CR accelerators
SN 1006

Radio synchrotronà Electrons up to GeV
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SN 1006

SN 1006

W44

X-ray synchrotron
VHE gamma-rays
GeV gamma-rays
à Electrons up to 100 TeV à Electrons up to 10 TeV à Protons up to GeV
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How to Es9mate CR Accelera9on
Eﬃciencies at SNR Shocks
NonthermalShock energy = Thermal energy +(CR) energy
3/16 mVs2

Proper mo9on of a shock
Hα

3/2 kT

Thermal Doppler broadening
HαHelder et al. (2013)

Helder et al. (2009)

Vs = 1200 km/s

kTp = 2.3 keV

CR accelera9on
eﬃciency < 30%
for the NE RCW 86

Measurements of CR accelera9on eﬃciencies have been s9ll scarce.
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High-Resolu9on X-Ray Spectroscopy:
A New Clue to CR Accelera9on Eﬃciencies
Kepler’s SNR
Calorimeter

This allows us tomeasure iontemperatures!!

X-ray CCD (’93-)
Gas Propor9onal counter(<~ ’95)

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GasCCD

Calorimeter

E/ΔE ~ 10

E/ΔE ~ 20

E/ΔE >~ 200

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The Hitomi Satellite
Telescope□ Hitomi:
SXS© ASTRO-H© ASTRO-H

HXI

The 6th Japanese X-ray astronomy satellite
Successfully launched on 2016/2/17
Lost its ground contact on 2016/3/26□ X-ray micro-calorimeter (SXS):-E/ΔE: ~200@1keV
Spa9al resolu9on: 1’FoV: 3’x3’ (6x6 array)
Dynamic range:
0.2-10 keV

Astronomy Picture of the Day(2016-02-18) © F.S. Porter
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Hitomi Observa9on of N132D
N132D with Chandra

SXS spectrum with an exposure 9me of
only 1 hr due to astude control failure

2 arcmin- Very bright in radio, op9cal,
X-ray, and gamma-rays- Core-collapse, ~2500 yr old
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Hitomi Collabora9on (2018)
accepted by PASJ on 2017-12-06
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S Heα & Fe Heα with the SXSFe K (17 counts)

S K (16 counts)

Doppler velocity wrt. LMC:
800 (50--1500) km/s
à Asymmetric ejecta
σFe-K ~ 11 eV à kTFe ~ 150 keV
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Doppler velocity wrt. LMC:
-65 (-450--435) km/s
à Swept-up ISM
σS-K ~ 4 eV à kTs ~ 90 keV

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Challenges with Gra9ngs on XMM/Chandra
XMM-Newton (RGS)

Chandra (H/LETG)

den Herder et al. (2001)

Canizares et al. (2005)

Reﬂec9on gra9ng

Transmission gra9ng

Slitless à Degrada9on in λ resolu9on:Δλ ~ 0.13 * Δext(arcmin) ÅΔextmin(spa9al resolu9on): 0.25’(E/ΔE ~ 200 @1keV; cf. E/ΔE ~ 20 for CCD)
Strong for rela9vely large sources(a few arcmin size is OK)
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Slitless à Degrada9on in λ resolu9on:Δλ ~ 0.67 * Δext(arcmin) ÅΔextmin (spa9al resolu9on): 0.01’

complementary Strong for small(”)-scale features
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Example Spectra of the RGS and HETG
E010240”

RGSSuzaku XIS

Chandra HETG (Flanagan et al. 2004)
HETG

C Lyγ

O Heα (r)O Heα (f)

O Lyα
O Heβ

O Lyβ

Ne Heα (f)Ne Heα (r)Ne LyαNe HeβXMM-Newton RGS (Rasmussen et al. 2001)- N132D (Behar et al. 2001)- B0540-69.3 (van der Heyden+2001)- N103B (van der Heyden et al. 2001)- DEML71 (van der Heyden et al. 2003)- 0509-67.5 (Kosenko et al. 2008)- 0519-69.5 (Kosenko et al. 2010)- 0506 (Broersen et al. 2011)

Wavelength (Å)

However, the RGS spectra are spa9ally integrated over the en9re SNR, andtherefore the interpreta9ons are complicated.
à Bright hot spots in Galac9c SNRs should be good sites for RGS spectroscopy.
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the line of sight.
XMM-Newton also has CCD cameras behind each of its three
mirrors, called the European Photon Imaging Camera (EPIC).
We use the spectra extracted from the EPIC data to measure
the electron temperature and abundances. All standard data
reductions and response matrix calculations were done withSAS, version 5.3.3. Background spectra for the EPIC data weretaken from a region outside SN 1006 but close to the centerof the field. As RGS background spectra we used archival data

still higher than that expected from Coulomb equilibration
alone behind a 3000 km s!1 shock. Figure 3 shows the predicted
kTe against net for current observations of the SN 1006 knot,
as well as the various ion temperatures. Our fitted net corresponds to plasma shocked 200–300 yr ago, which is predicted
to have kTe p 600 eV. Hence, we infer a small degree of collisionless electron heating (around 5% of the shock energy, i.e.,
Te /Tp ∼ 0.1; see Ghavamian et al. 2001) consistent with opticaland UV observations (Ghavamian et al. 2002; Laming et al.

A Knot in NW SN 1006
Vink et al. (2003)

Chandra view

Knot

Emission proﬁleKnot

Chandra image

NWSE

Fig. 1.—Left: XMM-Newton image of SN 1006 in the energy range 0.50–0.61 keV, which is dominated by O vii line emission (based on four different
Knot’ssize~contributing0.4’ (FWHM)
observations).
The areato the RGS spectra is indicated by the two lines. Right: O vii emission profile along the dispersion direction of the RGS(based on a combination of EPIC and Chandra data). The inset shows the profile of the bright northwestern knot (Chandra).
à RGS spectral resolu9on for O VII ~ 3 eV

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likelihood statistic of C p 93.6 for 104 data bins, with a possible
range of log ne t p 9.04–9.30. This is somewhat lower but ar-Temperature Nonequilibra9on: TO VII >> Te!
σ (O VII) = 2.4 ± 0.3 eV
kTO = 275 ± 70 keV
kTe = 1.5 keVTo >> Te !

O Heα(Vink+2003; Broersen+2013)resonance

forbidden

Very broad O K lines
à Large amount of
Do|ed line: emission model w/o broadening
ne emission modeled by broadened Gaussian-shaped lines. Right: O vii triplet.
thermal energy
Solid line: emission model w/ thermal broadening

otted line shows the best-fit model without broadening. The residuals are shown2017/12/18

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Shock Speed Measurements
Hα

X-ray

Raymond et al. (2017)

Proper mo9on measurement gives:
Vshock = 3000 km/s at a distance of 1.85 kpc(Raymond et al. 2017 see also Winkler et al. 2003; SK et al. 2013)

à Expected kTO = 280 (Vshock / 3000 km s-1)2 keV (@maximum),which agrees with the RGS measurement (à No energy for CRs).
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Considering Coulomb Equilibra9on

Katsuda & Tsunemi (2014)

No energy is le~ for the CR accelera9on.

However, this may not be true if the plasma was heated by a reverse shock.
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Ejecta Knots in SE Tycho’s SNR
Chandra image

Decourchelle et al. (2001)

XMM-Newton

C1, C2, C3

SuzakuC2No Cr Mn lines (Yamaguchi et al. 2017)2017/12/18

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Shock Speed Measurement
Chandra’s diﬀerence image (2000 - 2007)

Proper mo9on measurements:
Vshock = 4300 km/s at d = 3 kpc(SK et al. 2010)
à Expected ion temperatures:
kTOxygen = 580 (Vshock / 4300 km s-1)2 keV(σO Lyα = 4.1 eV)
kTFe = 2.0 (Vshock / 4300 km s-1)2 MeV(σFeL = 5.2 eV)

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RGS Observa9on in 2017
Obs. date: 2017-08-04
Exposure: 150 ks
PI: B. Williams, Co-I: SK

C1C2

C1’s emission proﬁle2017/12/18

C2’s emission proﬁle

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Ejecta Knots in Puppis A
Chandra imageviewKnotXM

c9oneridnoisre
M RGS disp

Observa9on date：2012-10-20
Exposure 9me：21 ks
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ONeMg-rich ejecta features(Winkler et al. 1985; SK et al. 2008; 2010)

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Emission Proﬁles (RGS Response)

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RGS Spectrum

2017/12/18~1.1Å

CTA Workshop @ U. TokyoO Heα (r) - KnotO Heα (r) - Filament

Spa9al displacement<-> Wavelength shi~
8 arcmin à 1.1 Å(Δλ ~ θ × 0.138/m Å)O Lyα - Filament

8’Region B

O Lyα - Knot

Lines from the knot and ﬁlament are detected!

~1.1Å

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2017/12/18

5Doppler velocity

1500 ± 200 km/s

Line width (σ)< 0.9 eV (àkTO < 30 keV)
CTA Workshop @ U. TokyoO Heα(r)O Heα(f)22

O Heα(r)O Heα(f)Filament

O Heα(f)O Heα(r)20O Heα(f)

O Lyα

Knot

O Heβ18
Region CWavelength (Å)

O Heα(r)

O Heβ

O Lyα

O Lyβ16O Lyβ
O Lyα0.514O Lyβ

50−51

O Lyβ

0.5

Ne Heα(r)Ne Heα(f)1Region B

O LyαSpectral Modeling

Ne Heα(r)Ne Heα(f)χ
10−16 cts s−1 Hz−1
χ
10−16 cts s−1 Hz−1

50−5 Blue=Knot Red=Filament Green=Total (incl. local BG)-650 ± 130 km/s

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Shock Speed Es9mate
Es.mate of a forward shock speed・Line-of-sight velocity: 1500 km/s
・Proper mo9on: ~0.12 ”/yr (Winkler et al. 1988) à 1260 km/s
à Gas mo9on: Vshocked gas = sqrt(15002+12602) = 2000 km/s
à Forward shock speed: Vshock = 4/3 Vgas ~ 2500 km/s
kTO = 195 (Vsh/2500 km/s)2 keV (@maximum, net = 0),
which is much higher than the upper limit of kTo < 30 keV
à Extremely high CR accelera9on eﬃciency ?!

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Coulomb Equilibra9on
Temperature evolu9on a~er shock hea9ng for Vshock = 2500 km/s
OxygenProtonObserva9on

ElectronThe kTo measured is signiﬁcantly lower than the value expected at Vshock = 2500km/s, even if we take into account the Coulomb equilibra9on.
à An extremely high CR accelera9on eﬃciency (> 85%)?!
However, this may not be true if the plasma was heated by a reverse shock.
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X-Ray Astronomy Recovery Mission
Telescope□ XARM:-© ASTRO-H© ASTRO-H

2017/12/18

The 7th Japanese X-ray astronomy satellite
To be launched in 2021
Carries X-ray calorimeter & X-ray CCD□ X-ray micro-calorimeter (SXS):- E/ΔE: ~200@1keV(Non-dispersive!)- Spa9al resolu9on: 1’- FoV: 3’x3’ (6x6 array)- Dynamic range:
0.5-25 keV

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Spectral Simula9on with XARM
XARM calorimeter spectrum (simula9on)

Suzaku’s XIS

FeL + NeKSi SFe

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A Li|le Thought about Synergy with CTA
CTA Collabora9on (2017)• CTA will reveal leptonic/hadronic contribu9on in SNRs,
as well as its spa9al distribu9on.

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X-Ray Measurements
Spa9al varia9on of TeV gamma-rays
Spa9al varia9on of proper mo9onsChandra

Spa9al varia9on of CR accelera9on eﬃciency
XARMTsuji & Uchiyama (2016)
Acero, SK, Ballet, & Petre (2017)2017/12/18

ASTRO-H white paper
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Summary• SNRs are the best candidates for Galac9c cosmic
rays. However, the CR accelera9on eﬃciency at
SNR shocks has been rarely measured.
• High-resolu9on X-ray spectroscopy is a hope tomeasure CR accelera9on eﬃciencies.
• Current measurements with gra9ngs onboard
XMM revealed CR accelera9on eﬃciencies(including upper limits) in a few SNRs.
• X-ray astronomy recovery mission (XARM) will
greatly enhance this ﬁeld.
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