Physics of Compact Stars

• Crab nebula: Supernova 1054

• Pulsars: rotating neutron stars

• Death of a massive star

• Pulsars: lab’s of many-particle physics

• Equation of state and star structure

• Phase diagram of nuclear matter

• Rotation and accretion

• Cooling of neutron stars

• Neutrinos and gamma-ray bursts

• Outlook: particle astrophysics

David Blaschke - IFT, University of Wroclaw - Winter Semester 2007/08

1

Example: Crab nebula and Supernova 1054

CHANDRA (BLAU) + HUBBLE (ROT)

1054 Chinese Astronomers observe ’Guest-Star’in the vicinity of constellation Taurus

– 6times brighter than Venus, red-white light

– 1 Month visible during the day, 1 Jahr at evenings

– Luminosity ≈ 400 Million Suns

– Distance d ∼ 7.000 Lightyears (ly)(when d ≤ 50 ly Life on earth would be extingished)

1731 BEVIS: Telescope observation of the SN remnants

1758 MESSIER: Catalogue of nebulae and star clusters

1844 ROSSE: Name ’Crab nebula’ because of tentacle structure

1939 DUNCAN: extrapolates back the nebula expansion−→ Explosion of a point source 766 years ago

1942 BAADE: Star in the nebula center could be relatedto its origin

1948 Crab nebula one of the brightest radio sources in the sky

1968 BAADE’s star identified as pulsar

2

Pulsars: Rotating Neutron stars

1967 Jocelyne BELL discovers (Nobel prize 1974 forHEWISH) pulsating radio frequency source (pulse in-terval: 1.34 sec; pulse duration: 0.01 sec)

Today more than 1700 of such sources are known in themilky way ⇒ PULSARSPulse frequency extremely stable: ∆T/T ≈ 1 sec/1million years

1968 Explanation of the phenomenon GOLD as ⇒ RO-TATING NEUTRON STARS, since:

– only Rotation explains high precision of pulses

– only small objects (R ≈ 10 km) can haveso small pulse duations

1969 Discovery of the pulsar in the Crab nebulaConnection established:SUPERNOVA - NEUTRON STAR - PULSAR

1968 Discovery of the binary Pulsar PSR 1913+16 byHULSE and TAYLOR (Nobel prize 1993)

3

What happens in a Supernova-Explosion ?

Two Szenarios after ceasing of nuclear fusion reactions in the star interior

• Supernova Type I (Carbon core): Explosive ’Burning’, star is completely destroyed

• Supernova Type II (Iron core): Implosion due to gravitational instability,subsequent shockwave explosion and neutrino emission ⇒

blast of the star envelope, star interior collapses ⇒ NEUTRON STAR or BACK HOLE

Neutron star-Properties:

• Radius: R ≈ 10 km

• Density: ρ ≈ 1014 . . . 1015 g/cm3

• Mass: M ≈ M = 2 × 1030 kg

• Rotation: Period T < 1 sec,for progenitor star T ≈ 30 d(Sun)

• Magnetic field: contraction increasesthe density of field lines dramatically→ H/Hearth ≈ 1012

4

Pulsars: Laboratories for Many-particle Physics

Glitches: Superfluid Nuclear Matter

Julian Date −2440000.5

1980

02000 4000 6000

Freq

uenz

y f

(Hz)

11.21

11.208

11.206

11.204

11.202

1970 1975

Nature of Glitches: Vortex-Crust Unpinning→ suddenly smaller momet of inertia→ jumpin Ω = dφ/dt (angular momentum conserva-tion)

Lecture: Astronomie II online, Notebook University Rostock (NUR)http://www.mpg.uni-rostock.de/tap/astro/

5

Phase diagram for QCD Matter at high densities

Quark Matter

Novae

AGS Brookhaven

SIS Darmstadt

CERN-SPS

Super-

Quark-Gluon-PlasmaC

ON

FIN

EM

EN

T

1 3

[T

=14

0 M

eV]

H

[n =0.16 fm ]ο

1.5

0.1

-3

DECONFINEMENT

FAIR (Project)

RHIC, LHC (construction)

Hadron gas

Nuclear matter

QC

D -

Lat

tice

Gau

ge T

heor

y

Neutron / Quark Stars

Baryon Density

Tem

pera

ture

Big Bang

Heavy Io

n Collisions

COLOR SUPERCONDUCTIVITY

Challenge toExperiments

and Questions toTheory:

• How do Quarks get theirmasses (χSB)?

• Why are there no free Quarksand Gluons (Confinement)?

Virtual Institute (2003-06): “Dense hadronic matter and QCD phase transitions”(UNIs Bielefeld, Darmstadt, Frankfurt, Giessen, Rostock, Tubingen mit GSI Darmstadt)

6

Equation of State and Stability of Compact Stars

Tolman-Oppenheimer-Volkoff Equations

1. Stability: General Relativistic Hydrostatic Equilibrium

dP (r)

dr= −G

m(r)ε(r)

r2

(

1 +P (r)

ε(r)

) (

1 +4πr3P (r)

m(r)

) (

1 −2Gm(r)

r

)−1

NEWTON EINSTEIN CORRECTIONS GENERAL REL. THEORY

2. Mass Distribution: m(R) =∫ R

0 ε(r) 4π r2 dr

0.2 0.4 0.6 0.8 1n [fm

-3]

101

102

P [

MeV

fm

-3]

Flow constraintDBHFη

D = 0.92, η

V = 0.0

ηD

= 1.00, ηV

= 0.5η

D = 1.03, η

V = 0.5

ηD

= 1.02, ηV

= 0.5

8 10 12 14R [km]

0

0.5

1.0

1.5

2.0

2.5

M [

Msu

n]

RX J1856

0.3

z = 0.1

0.2

0.40.50.6

causality constra

int

EXO 0748-676

XTE J1739-285

DBHF (Bonn A)η

D = 0.92, η

V = 0.0

ηD

= 1.00, ηV

= 0.5η

D = 1.02, η

V = 0.5

ηD

= 1.03, ηV

= 0.5η

D = 1.00, η

V = 0.0

4U 1636-536

0.7

4U 0614 +09

7

Rotation and Star Structure

Axially symmetric solutions of the EINSTEIN-equations for compact stars show::

• Deformation (Excentricity)

• new density distribution (centrifugal forces)

• further general relativity effects0 2 4 6

Ω [kHz]0 2 4 6

Ω [kHz]

0

3

6

9

12

15

r [k

m]

0 2 4 6Ω [kHz]

NB=1.55 NONB=1.3 NONB=1.8 NO

QM

HH

H

M

M

Q

Re

Rp

Re

RpRp

Re

Phase transition to Quark matter depends onMass (Baryon number N ) and Angular veloc-ity (Ω = dφ/dt) of the Star!

Phase diagram (Ω − N plane) =⇒

visualizes observable Signals:

• Braking index (spin-down)

• Population-clustering (accretion)

Moment of inertia ⇐⇒ Phase transition! 1

1.25 1.5

1.75 2

2.25

24

68

1

1.25 1.5

1.75 2

2.25

24

68

Ω

N

150

Quark Core Stars Bla

ck H

oles

6066

72788490

96

No Stationary Rotating Stars

102

Hadronic Stars

108114 120

126

132144

0

2

4

6

[k

Hz]

.1.25 1.5 1.75 2.0 N/N

Ω

8

Low-mass X-ray Binary (LMXB)

LMXB’s show:

• Accretion (N - Evolution)

• X-ray bursts with quasiperiodicBrightness Oscillations (QPO’s)

• further general rel. effects (ISCO)

1.2 1.4 1.6 1.8 2 2.2N [N

sun]

0

1

2

3

4

5

6

7

8

9

10

Ω

kHz]

0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

ν [

kHz]

No Stationary Rotating Stars

Hadronic Stars

Quark Core Stars

Bla

ck H

oles

Ωmax(N)

Ncrit

(Ω)N m

ax(Ω

)

0.6 TG

1.0 TG

over 100 million yearsabout 60 million years

Phase transition Signal:Population clustering at Ncrit(Ω)

QPO-Phenomenon gives informations about:

• Mass-radius relation

• Rotation frequency

Ω−N plane ⇐⇒ Hertzsprung-Russell-Diagram for QPO’s!

9

1 2 3 4 5 6 7

log(t[yr])

5.6

5.8

6

6.2

6.4

log(

Ts [K

])

RX

J08

22-4

3

1E 1

207-

52R

X J

0002

+62

PSR

065

6+14

PSR

105

5-52

RX

J18

65-3

754

Vel

a

Gem

inga

PSR

J02

05+

64 in

3C

58

Cra

b

CTA 1

1.101.214 critical1.2171.251.321.421.51.651.751.793

Cooling of Hybrid stars with 2SC Quark coreHJ (Y - 3P2*0.1) with K = 240 MeV with Med. effects, our crust, Gaussian FF

• Enhanced Cooling by URCA ⇒ Signal

• 2SC+X phase, ∆X ∼ 30 keV

• Pulsar in 3C58 - candidate for a Quark Star?

Grigorian, DB, Voskresensky: Phys. Rev. C 71(2005)

γ

γ

γγ

γ

γγ

γ

γ

T =40 MeV

νe

ν

T = 0

e

νeνe

νe

νe

νe

γ

QM

γ

γ

γ

γ2SC

Neutrinos carry energy off the star=⇒ Cooling evolution given by

dT (t)

dt= −

εγ +∑

j=URCA,... εjν

∑

i=q,e,γ,... ciV

-

u

e-

ν

d

Cooling of Compact Stars-Results

10

Magnetic Quark Star: Neutrino Beam – Gamma-Ray-Burst

• Neutrinos trapped in a star when temperatureT > 1 MeV (≈ 1010K) → mean free path R

• 2SC quark matter core with magnetic vortices (B∼ 1016 G)

• Beamed emission neutrinos, ∆E ∼ 1052 erg

• Conversion of neutrinos → photons: Gamma-Ray Burst (?)

1e+50

1e+51

1e+52

1e+53

L [

erg/

s]

B = 1013

G

B = 1014

G

B = 1015

G

B = 1016

G

B = 1017

G

10

20

30

T [

MeV

]

0.1 1 10 100 1000t [s]

0.01

0.1

1

θ ν[g

rad]

R

θν

ν,ν

ν,ν

G G

G

νν γ

γ

e+e

conversion

star surface

vortex

λν

superconductor

11

Puzzling Compact Star Phenomena - Quark Star Candidates?

Quasiperiodic Brightness Oscillations (QPO’s) inLow-mass X-Ray Binaries (LMXB’s)⇒ Limits for Mass - Radius - Relation⇒ 2 M too large mass for quark stars?

⇐ Rossi-XTE LMXB ⇒

Gamma-Ray Bursts (GRB), extragalactic, extremelybright, Connection to Supernova Explosions⇒ Which Engine ∼ 1052 erg ?

⇐ INTEGRAL GRB 990123 ⇒

Isolated X-ray source (RX J18565),17 km radiation radius⇒ too big for a Neutron Star?

⇐ HUBBLE RX J1856.5-3754 ⇒

Pulsar in Supernova Remnant (3C58; AD 1181)with Temperature T = 106 K⇒ too cold for a Neutron Star?

⇐ CHANDRA 3C58 ⇒

12

Wide variety of supernovas - progenitor mass dependence

13

Supernova Collapse in the Phase Diagram

108

109

1010

1011

1012

1013

1014

1015

density ρ [g cm-3

]

100

101

102

tem

pera

ture

T [M

eV]

Supernova evolutionin the phase diagram

2SC

Nuclear matter

14

Supernova Collapse in the Phase Diagram (II)

108

109

1010

1011

1012

1013

1014

1015

density ρ [g cm-3

]

100

101

102

tem

pera

ture

T [M

eV]

15 Msun

(Harald Dimmelmeier)

Supernova evolutionin the phase diagram

2SC

Nuclear matter

15

Supernova Collapse in the Phase Diagram

108

109

1010

1011

1012

1013

1014

1015

density ρ [g cm-3

]

100

101

102

tem

pera

ture

T [M

eV]

15 Msun

40 Msun

(Harald Dimmelmeier)

(Tobias Fischer)

16

The case of SN2006gy

17

The case of SN2006gy - a Quarknova ?

Discovery: Sept. 18, 2006in NGC 1260 (Perseus)Distance: 72 Mpc=238 Mill. Ly(Smith et al.: astro-ph/0612617)

Light curve: 70 days rise timeEnergy release: 1052 erg= 10 betheProgenitor star: ≈ 150 M ?Engine: Quark-star formation?(Leahy & Ouyed: 0708.1787 [astro-ph])

18

Equation of State for Supernova Applications

Supernova 1987A - 20 years later:

• Big mystery of rings!

• Double degenerate core in com-mon envelope?

• 2.14 ms periodic signal

• Explanation for 99% of GRB ?

Middleditch, 0705.3846 [astro-ph]

19

What has happened here ??

Equation of State for Supernova Applications

Supernova 1987A - 20 years later:

• Big mystery of rings!

• Double degenerate core in com-mon envelope?

• 2.14 ms periodic signal

• Explanation for 99% of GRB ?

Middleditch, 0705.3846 [astro-ph]

20