Magnetic Activities of Magnetars
and X-ray Observations
マグネターの磁気活動とX線観測
Overview of the NS diversity, magnetars, and future projects

Teruaki Enoto
NASA Goddard Space Flight Center
RIKEN High Energy Astrophysics Laboratory
第２回 DTA シンポジウム「コンパクト天体の活動性と磁気的性質」
1

Neutron Stars: Lab. for the Fundamental Physics
Dense nuclear matter, strong gravity, rapid rotation, and strong magnetic field
Rotation Period P ~ 1 s(~2 ms -- 5 hour)(Angular momentum)

Supernova Remnant
Pulsar Wind Nebula

NormalStar

Temperature T ~ 106 K

Source ofDiversity(~105 K --107 K)

NS•

Accretion Rate M

Important for theEquation of State
Magnetic Field B ~ 1012 G(~108 G --1015 G)

1 T = 104 G

Mass M ~1.4M⊙ (~1.0M⊙--2.0M⊙)
Radius R~12 km (~8 km--14 km)

Wide Range of Fundamental Quantities + Surrounding Environment= Diversity of Neutron Star (Zoo)
Astronomically Interesting & Physically Important (for e.g., EoS)
2

10

(soft gamma repeater)

15

AXP

Canonical
rotation
poweredpulsars

14(anomalous X-ray pulsar)

HMXB w/ CRSF

(Cyclotron Resonance
Scattering Feature)B ~ 1012 G
B-fielay
1.0SNeP~10 msd dec

21h210100
1 50
Energy(keV)# ofsource01

102 20 103
Spin period(s)(s)Period21001

101101

10-1

P · Ṗ

1-10-2

B

710-3

D

X-ray spectrum
24L
B/P
mag
4U 0115+63(Santangelo+99)
8108

taeenliṖ /P 3
9109

Lrot
0.01

1010

01

keV cm-2 sec-1 keV-1

NS = Rotating Magnet
1110113110131012

BQED = 4x1013 G

41

10“Magnetars”
SGR

51

Measured Magnetic Field (G)P~2-12 s1016

GlowingClass!!
61

Surface Magnetic Feild (Gauss)Magnetic Field and Evolution of NSs

Surface Magnetic Field

Strongly magnetized NSs has been implied in recent studies.
3Soft Gamma Repeater (SGR)
Discovered by “Giant Flares” or recurrent burst activities. ~ 5 SGRs
fireball?

L > 8.3x1044 erg/s

1040.35 seca few hundred millisecond
empirically two Blackbody

SGR 1900+14

Astron. Phys. Lett.
Enoto+2009

SGR 0501+4516(c) Duncan

100

103
102

Short Bursts

keV2 (sec cm2 keV)-1X⥺࢝࢘ࣥࢺ(0.5⛊)-1-1
X-rayCounts (0.5 sec)

Giant Flare (3 events)

400 sec

10Hurley+2005

E = 1.2x1044 erg(kT~20 keV)
100

200Time᫬้(sec)⛊300

400

Hurley+07

10kT~3 keV(R~ 8 km)11

kT~15 keV(R ~ 0.5 km)

10Energy (keV)

100
Enoto+09- Exceeding the Eddington Luminosity (~1038 erg/s) by ~6 orders of magnitudes- B > 1014 G is required to confine a few dozen keV plasma for ~400 sec
4

Anomalous X-ray Pulsar (AXP)
Discovered as pulsed bright persistent X-ray sources. ~15 AXPs
Associated with SNR

Persistent X-ray Emission
4U 0142+61

Photons / (cm2 s keV)

1E 1841-045 (SNR Kes73)

Pulse Period

10-2White+96

10-3

10-4

kT ~ 0.4 keV quasi Blackbody(Detected from all the AXPs)
Standard Neutron Star ~0.08 keV

Chandra Image (c)CXO

0.5

12Energy (keV)- Exceeding the Spin-down luminosity by ~2 orders of magnitudes (Lx >> Lsd)

5

Persistent X-ray Luminosity of SGR/AXP・LX / Esd (Spin-down Luminosity)104
1E1841

J1708

Energy Source?

4U0142

1E2259

SGR0526
J0100
SGR1900
1E1547
SGR1806
SGR0501
1E1048100J1647
・Lx = Esd

1J1714

J1622

Crab Pulsar0.01

XTEJ1810

Enough Rotation Energy

SGR1627
PSR 1509-58

Geminga

Enoto+1210í

0.1

110103104

Characteristic Age (τc)
Lx >> Spin-down Esd, no evidence for a binary companion (e.g., Kaspi+99)
Magnetars; Magnetically-powered Pulsars?
6“Magnetar Hypothesis”“SGRs and AXP are ultra-strongly magnetized NSs with B~1014-15 G
powered by their stored magnetic energy in the stellar interior.”
Thompson & Duncan+95, 96

1. SNR association, slow P and large Pdot

Young (τ<100 kyr) & B~1014-15 G

2. Lx >> Lsd by 2-3 orders of mag. Not rotation-powered pulsars
3. No evidence of binary system Not accretion-powered pulsars
4. Marginal “proton” cyclotron resonance Suggests B > 1014 G
5. Peculiar burst activities Magnetic dissipation (e.g., reconnections)??
6. Super-Eddington giant flares B > 1014 G & suppression of σ

QED Critical Field
Suppression of σDistortion of atom

Photon Splitting

Birefringence7

o. 2]

Suzaku Observation of Anomalous X-Ray Pulsar 4U 0142+61

Multi-wavelength Emissions of the Magnetar Class
Energy-domain viewpoint

OpticalPulse-profile

InfraredSoft-X

Hard-XX-rays

Gamma

Radio

• AXP 4U 0142+61 Persistent Emission• No high-E emission >1 MeV so far (e.g., Fermi)
Radio emission is rare (only transients?)•
Enoto 2011 PASJ
• Weak infrared and optical emissions• Soft and hard X-rays are dominant components• Soft-X: quasi-black body kT~0.3 keV
Fig. 8. Multi-band spectral energy distribution of Hard-X:
4U 0142+61. non-thermal
The Suzaku data are Γ~1?
shown in cutoff
the 0.8–10>
keVand 12–200
keV energy ran
750keV?
•the XIS and the HXD, respectively. The soft and hard components of Model E are represented by dashed lines after corrections for the inabsorption, and are extrapolated to lower energies.
The
previous
X-ray results are also
the 0.1–200
keV band from the XMM-Newton
Bothcomponents
areshown:highlypulsed.
•et al. 2007; Abdo et al. 2010) and the INTEGRAL/ISGRI data sets (den Hartog et al. 2008). In the gamma-ray energy band, the 2 ! CGRO/COmagnetars
exhibitthearesoft
emission.
• (Almost)upper limits (den Hartog et al. 2006; Kuiperet al. 2006) and all
95% theFermi/LAT
upper limits (Abdoet al. 2010)
plotted.
In the infrared and optic

Spitzer observations at 4.5 "m and 8.0 "m (Wang et al. 2006) and some data sets from Gemini and Keck II (Durant & van Kerkwijk 2006c; Het al. 2004) are shown, where the optical data are de-extincted assuming a reddening value of AV = 3.5. In the radio band, a 2 ! upper8 li

2
1.5

GSO 50-150 keV

0-0.2

00.2

0.4

0.6
Time (s)NuSTAR
10Suzaku
Swift

10.5
-0.6

-0.4

-0.20Burst-80

0.20.4

SwiftX-ray counts (a.u.)

1E 1547.0-5408

Chandra015-70 keV

10-70.0 keV

TE+103

Burst detection
Prompt follow-up2



8XI0 2.0Olausen+2013
6




Suzaku







4
2
RXTE

Figure 1. Number of confirmed magnetars discovered over time.
Labels in italics indicate the source was either discovered or later
detected by an all-sky X-ray/soft gamma-ray burst monitor. The
dashed and dot-dashed lines mark the launches of Swift in 2005
and Fermi in 2008, respectively.

6PIN 10.0-70.0 keV0150 keV




0

50.4 sBurst-9










-2


1050.6Time (s)0.0SwiftkeV has detected 1-2 magnetar XI0
2.0-10.0 keV
outbursts
per yearincreasing number of confirmed magnetars (~20).

GSO 5020

4The McGill M

Discoveries of New Magnetars

150 keVGSO 50-150 keV
Preciselocalization

1PIN 10.0

which were later detected (and therefore could have been
discovered) by one, are highlighted in italics,
4 for this reason.
Many known magnetars have thus been found via their
2
bursting behavior, which raises an important
point regarding how they are named. Because burst monitors
have tended to find them, magnetars 0have often been
named with the designation “SGR” in recent years (seeTables). We argue strongly that this naming conven4
tion requires amendment because as discussed
in thisGSO
50
work and extensively elsewhere (e.g. Gavriil etal. 2002;
Kaspi et al. 2003; Woods & Thompson 3
2006; Mereghetti
2008; Kaspi 2010; Mereghetti 2013; Rea & Esposito
2 designated as2011) the distinction between sources“AXP” and “SGRs” has been largely erased via the dis1 previously ascovery of objects which have properties
cribed to both categories. It is today very hard toclassify some sources as one or the 0other; rather it
0.2
0.4
0.6
-0.6
-0.
has become clear that there is a continuous
spectrumof magnetar-type activity which can even include some
9Hard X-ray
detection

Periodmeasurement

Magnetars are a glowing new class of NS: A key to understand NS diversity.
0-0.2

00.2

0.4

0.6
Time (s)-0.6-0.4-0.20Time (s)Co

10.50X-ray
OutburstofAXP
1E
1547.0-5408(1)-0.6 -0.4 -0.2
00.2
0.4
0.6-0.6 -0.4 -0.2
00.2

0.4

4041030

2009Burst-8
January 22 Suzaku/WAM

Burst-7

3 hour20103
1004:00

08:00

4 hours

XI0 2.0-10.0 keV

12:00
0100
10

Enoto+12PIN 10.0-70.0 keV

40

Light Curve

16:00

020:00(a4)10.0-70.0PINkeV(1) CutPL

Enoto+12(2) 2BB

510Crab Nebulaï20031

GSO 50-150 keV

220

Suzaku/HXD-WAM

500:00060

10

XI0 2.0-10.0 keVï

105-2 s-1 cm-1 )keV
keV2keVcm(PhotonskeVCount Rate (cnt/s)
Rate (cnt/16 ms)
s-1)-1
Count (15.6 ms)-1 Count (15.6 ms)-1 カウントレート
Count (15.6 ms)(cntsTime (s)Known as a fast rotation faintAXP (P~2 sec)

0.6Time (s)200 ms10-0.6-0.4

-0.2

00.2

0.4

0.6 (sec)
Time (s)Spectrum210.10

GSO 50-150 keV

01-0.6 1 -0.4

10-0.2100 (keV)0.2
Energy100100

Energy (keV)0.40.6Time (s)Feature1: Recurrent Bright Short Burst
Figure5. Light
curves ms,of theindividual short
events spectrum
detected bytheSuzak
Duration~100-500(Empirically)
Twoburst
blackbody(kT~ present4, 11 keV)refer to those obtained with XIS0, with HXD-PIN, and with HXD-GSO, in the 2–10, 10–70
10
is 15.6 msec.

X-ray Outburst of AXP 1E 1547.0-5408 (2)-1-2-2))
cmレート (cnts s-1) Absorbed
X ⥺ࣇࣛࢵࢡࢫ
Flux (erg (ergs-1 scmCountRate (cnt/s)
カウントレート(cnts s-1)

Known as a fast rotation faint AXP (P~2 sec)
2009 January 22 Suzaku/WAM

105

3 hour104

Suzaku/HXD-WAM

4 hours

103
00:00

04:00

08:00

12:00

16:00

20:00

10-8
10-9
10-10
10-11

Swift/XRT

Thermal X-rays (2-10 keV)

6 monthSuzaku/XIS

Suzaku ToO

Suzaku follow-up

10-12
10-13

1 year

1 mCrab level

Sep
2007

Mar2008

Sep
2008

Mar
2009

Sep
2009

Mar
2010

Sep
2010

Mar
2011

Sep
2011

105

Suzaku/HXD-WAM
Feature2: Persistent X-ray becomes3 hourbrighterby 2-3 ordersof magnitude.
10411

X-ray Outburst of AXP 1E 1547.0-5408 (3)Suzaku ToO Observation 2009 January (33 ks)

keV2 (Photons cmï sï keVï)

1Hard Comp.

Thermal (surface)0.1

Γ ~ 1.5

kT ~ 0.7 keV

0.01
10ï
10ï
10ï

kT~0.4 keV

10ï12006 XMM Observation(Gelfand+07)
10100
Energy (keV)

Enoto+09

Hard X-rays were clearly discovered during the magnetar outburst.
Follow-up observation confirmed the hard component one year after the outburst.

Feature2: Persistent X-ray becomes brighter by 2-3 orders of magnitude
Both components (soft thermal + hard X-rays) become brighter
12

X-ray Outburst of AXP 1E 1547.0-5408 (4)Before Burst

2009Outburst

X-ray countrate

4-34 keV

Kuiper+12

11-34 keV
After Burst△(Spin Frequency)
4-34 keV

11-34 keV

Feature3: A frequency derivative jump at the outburst (Pulse profile change around the onset of the burst

˙/ =0.69 ± 0.07 )Hot spot?

13

Magnetar Outbursts
Heat Conduction
Hot Spot

Thermal X-rays

Hard X-ray

outer crust
Poloidal Field
Accelerated
Bp ~ 1014-15 G particle

inner crustouter core

Short Burst

Higher multipolecoreMagnetosphere Deformation
Reconnection
Fireball

Starquake@crust

EmagneticEthermal(glitch etc)

Toroidal Field
Bt ~ 1015-16 G ?

Energy Reserver
14Surface and Magnetospheric Emission
Hard

High-B, Young

SGR
1806-20 (2.1x10(0.22 kyr)11 T)
SGR 1806-2010 T)
1E1E
1547.0-5408(1.4 kyr)1547-54 (2.2x1010 T)
1RXS
J1708-40 (4.7x10(9.01RXS
J170849.0-400910kyr)
10
4U 0142+61 (1.3x10 T)(Enoto+2010, ApJL) 4U 0142+61 (70 kyr)110Energy (keV)

Photon index Γh / /+DUGQHVV5DWLRȟhs

2-1keV(phcm-2-1s-1 keV)
2-2-1keVnormalized
cm secat keV
2 keV (a.u.)

ThermalLow-B, Old

10
3.0High-B, Young

0501+45(2009)

1900+14

2.0

1
1.0

0.0
0.1
-1.0

1806-201547-54

1547-540501+45
1806-20(a)

1900+14(2008)

1708-40
1841-040501+45(2008)

1841-04

2259+58

1708-400142+610142+61

1E 2259+58(Enoto+2010,
Astro. Phys. Lett.)

Low-B, Old

100

0.11010 11011 100
10Characteristic
Magnetic Fieldage(G)(kyr)

Magnetospheric hard X-rays were detected from 7 sources (+1 candidate).

• Ratio of soft and hard X-ray luminosities (ξ=Lh/Ls) is found to be positively correlated•with B-field by period P and its derivative Pdot.
Photon index of hard X-rays becomes harder toward low B-field old sources.

Spectral EVOLUTION as a function of B-field.
(e.g., photon-splitting down-cascade in the QED field magnetosphere?)
TE et al., ApJL, 201015

Hard X-ray emission mechanism
Thermal Bremsstrahlung ?

Resonant Compton up-scattering?

(Thompson & Beloborodov 05)(Baring & Harding 07)
hard X-rays

resonant magnetic
Compton up-scattering
Transition layer

relativistic e+/esoft X-rays

star surface

star surface

Photon Splitting Effect?
(Harding+97; Enoto+10; Takata+12)

No model has not yet explained theobserved properties of magnetars.
Observational & theoreticalprogress is strongly required.

softening(photon split)

strong field~MeV sourcestar surface

And also other models;
Heyl & Hernquist 2007
Trumper+2010
Kuiper+2006
16

Magnetar Outbursts
Heat Conduction
Hot Spot

Nobody has
seen this..

Thermal X-rays

Hard X-ray

outer crust
Poloidal FieldAccelerated
Bp ~ 1014-15 G particle

inner crustouter core

Short Burst

Higher multipolecore

Magnetosphere Deformation
Reconnection
Fireball

Starquake@crust

EmagneticEthermal(glitch etc)

Toroidal Field
Bt ~ 1015-16 G ?

Energy Reserver
17Toroidal Magnetic Field
Huge energy reserver is needed inside the magnetars
Strong toroidal Field inside NSs? (can not be measured by P-Pdot)
AngularMomentum

Axis ofsymmetry
X3L

Maximum
photonemissivity
ξ

4U 0142+61 Suzaku Spectrum
Enoto+2011

Braithwaite+09
PoloidalToroidalFree Precession with period Q
Toroidal B-field=II10 4Prolate shape
Bt1016 G2X3 ≠ ξ

Q=Pspin(C) http://faculty.ifmo.ru/butikov/Applets/Precession.html(see., e.g., Landau & Lifshitz textbook)18

Reduced chisqu

Evidence for Precession

which agrees
with previous measurements of the pe
100of this source and its derivative [20]. The folded
50 profile is shown in Fig. 2 (a).
X-ray pulse

Prototypical AXP 4U 0142+61 (P=8.69 s, Poloidal field Bd~1.3x1014 G)

060

120

180

240

300

360

2Zn /2n (16 bins)
Reduced chisquare

100

1.050

0.5

0
3.0
4.0
2.522.0
3.0

20
15

1.0

10

1.0
0.5

00

5

8.687
8.687

8.688
8.688

8.689
8.689

Period (sec)

8.690
8.690

0

8.691
8.691
35

Z4 /8(c) HXD-PINTest Search Period (s)30(demodulated)
25 via16FIG. 1: (a)
A
1–10
keV
XIS
periodogram,calculated
3.0
Toroidal B-field Bt ~ 10 G
dard folding analysis using 16 phase bins per cycle. 20Data
416
2
2.0 and XIS3 were10
XIS0, XIS1,
co-added,
withoutb(B/10G)removing
15ground. (b) Periodograms from the background-inclusiv
1021.0 data, calculated using the Z technique
40 HXD-PIN
n52

1025

4.02

1.6430Z48.69 s
1.5 h35

1.5
2.0

Hard X-ray shows a sinusoidal, T=1.5hour, phase modulation (amplitude 0.7 s)
Makishima, TE et al., PRL, 2014(b)Magnetosphere
HXD-PIN
Magnetosphere(c)
HXD-PINn=4n=3HardX-ray
HardX-ray(demodulated)(>10(>10 keV)
keV)
AFTER
BEFORE

20

1.5

Z4

0.2

0.4

0.60.8(precession search)(b)(a) HXD-PINXIS
Surface200
Hot n=3Spot n=4
2.5(0.2-10 keV)
2.01503.0

Zn /2n Z42 /8

Z42 valueSignificance of Pulsation

Significance Map

1.01.225019

Magnetar Outbursts
Heat Conduction
Hot Spot

Nobody has
seen this..

Thermal X-rays

Hard X-ray

outer crust
Poloidal Field
Accelerated
Bp ~ 1014-15 G particle

inner crustouter core

Short Burst

Higher multipolecore

Magnetosphere Deformation
Reconnection
Fireball

Starquake@crust

Emagnetic

Ethermal(glitch etc)

Toroidal Field
Bt ~ 1015-16 G ?

Energy Reserver
20

Hot spots heated by the internal B-field?

Other X-ray pulsarsvolume B-field dissipation emissiondB
Field decay:
=dtkT

1900
0142

● Persistent (Suzaku)★ Transient (Suzaku)■ Other NSs
Harbel+2006; Pons+2007

surface area &temperature

S, T

1708

10-1

0.5

B

1822 0501
1547
1647
1048

2259

aB

1806

10-2

10-2

10-1

1

10

0.1 keVTransient Source (Suzaku)

1.0 keV

Persistent Source (Suzaku)

0.01 keV

Ethermal
B2= S 1T 4
8
Surface Temperature kT (keV)

Emagnetic
dS R
dt

Surface Temperature kT (keV)

Magnetic Field B (1014 G)

thickness△R

One support for the magnetic energy dissipation
Enoto+in prep21

10“Magnetars”
SGR(soft gamma repeater)

15AXP

51

(anomalous X-ray pulsar)

1014311013

211012111011

SGR 0418+5729
011010hen
liDiscovery of

DLow-field magnetar

5Energy (keV)

10201

22101

1

1102
103
Spin period(s)(s)
Period01

101-(Rea et al., Science 2010)710-2

SGR 0418+5729
B10~-1 6x10121 G

Toroidal Field ?
810-3

tae

Tiengo et al., 2013, Nature
B > 2x1014 G (proton cyc.)
9109
108

BQED = 4x1013 G

41

Measured Magnetic Field (G)P~2-12 s

1016

GlowingClass!!
61

Surface Magnetic Feild (Gauss)

Discoveries of Low-Field Magnetars# of source

Surface Magnetic Field

Population of hidden magnetars is larger than previously expected?
22Summary

16/16• Magnetic field (B~108-15 G) is one of origins of the NS diversity.
B~108-15 G に及ぶ磁場が中性子星の多様性を作り出すひとつの要因である。

• There is growing evidence that some compact objects are
powered by the stored huge magnetic energy with B~1014-15 G.
1014-15 Gを超える磁場をエネルギー源とする星の存在が確立しつつある。
Examples:• Evolution of surface & magnetospheric radiation (Enoto et al., ApJL 2010)• Toroidal field indicated by NS free precession (Makishima et al., PRL 2014)• Low-field magnetars with a cyclotron feature (Tiengo et al., Nature, 2013)• Complementary two X-ray observatories will be launched soon
相補的な２つのＸ線観測ミッションが 2015, 2016年に打ち上げられる。

• 2015: ASTRO-H, High resolution spectroscopy + wide-band• 2016: NICER, Large effective area + high time resolution.

23