Welcome from Peking University!

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

Astronomy Dept., School of Physics

4 groups:Galaxies and Cosmology (Prof. Z. H. Fan)

Planet nebula physics (Prof. X. W. Liu)

AGN and supermassive BHs (Prof. X. B. Wu)

Particle astrophysics (Prof. R. X. Xu)

KIAA (Kavli inst. for A&A at Peking U.)…

Pulsars & Quark stars

Renxin Xu (徐仁新 )School of Physics, Peking University

Talk presented at“Workshop on high energy astrophysics”July 25th, 2006. Astron. Dept., Nanjing

Univ.

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

Not only is the Universe stranger than we

imagine, it is stranger than we can imagine.

—— Arthur Eddington

What’s the nature of pulsars?

Thought conventionally to be normal neutron stars

• But no convincing work (either theoretical from first

principles or observational) has confirmed Baade–

Zwicky’s original idea that supernovae produce

neutron star

To be quark stars?“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

Summary

A historical note on pulsarsA historical note on pulsars

Obs. hints of quark stars?Obs. hints of quark stars?

ConclusionsConclusions

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

It depends on laboratory physics laws to understand astrophysical phenomena!

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

Statistical Laws

M-B statistics

EoS of Stars

BE FD

Main-sequentstars

Fermionstars

L. LandauS. Chandrasekhar

Maybe there are stars with

nuclear density after collapse?

Degenerate pressure is not omnipotent in standing against the gravitational collapse

“Neutron” star

R. H. Fowler (1926, soon after FD)

A historical note on pulsarsA historical note on pulsars

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

Walter Baade and Fritz Zwickyproposed in 1934 that supernovaecould produce cosmic rays andneutron stars …

Pulsars (discovered in

1967) could be neutron

stars?

A. Hewish

A historical note on pulsarsA historical note on pulsars

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

Quark? A historical note …

M. Gell-Mann (1969)

Quarks?

1950s~1960s: A success in

the classification of hadrons

discovered in cosmic rays

and in accelerators

M. Gell-Mann (1964):

Quarks? ---- in mathematical

description, rather than in

reality.

Zweig (1964): in reality?

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

Quark? A historical note … Chinese group (1966)

Experimental evidence for the last one: top quark in 1995

Experimental evidence for asymptotic freedom

A historical note on pulsarsA historical note on pulsars

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

The Nobel prize in Physics (2004)

David J. Gross (L) of the University of California at Santa Barbara and his wife (R)

Frank Wilczek of the Massachusetts Institute of Technology.

H. David Politzer of the California Institute of Technology, Pasadena, California.

1973: SU(3) non-Abelian gauge theory asymptotic freedom

What is Quark Matter?

Expected in QCD

To be a direct consequence of aympt. freedom

T

A simple QCD phase diagram

(Hadron gas)

(QGP)

A historical note on pulsarsA historical note on pulsars

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

Pulsars: quark stars?Ivanenko & Hurdgelaidze (1969)

Itoh (1970)

Bodmer (1971)

Asymptotic freedom

Witten (1984)

1986: Haensel et al.; Alcock et al.

A historical note on pulsarsA historical note on pulsars

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

The structure of normal Neutron stars

Heiselberg 2002

Atmosphere

Outer crust

Inner crust

Neutron matter

Core ？

A historical note on pulsarsA historical note on pulsars

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

http://chandra.harvard.edu/photo/2002/0211/0211_illustration.pdf

Neutron Stars

v.s.

Quark Stars

A historical note on pulsarsA historical note on pulsars

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

Solid Quark Matter?

B

T0 QCD phase?Phase diagram for CO2

Solid?Liquid?

Gas?Hadron

QGP

A historical note on pulsarsA historical note on pulsars

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

T deconfinement

chiral sym. restor.

A Solid-quark-matter conjecture

Solid QM?

T-dom.

D-dom.

Xu 2005

Similar to the superconductivity symmetry

broken spontaneously

A historical note on pulsarsA historical note on pulsars

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

Radio pulsars

Accretion-powered X-ray pulsarsX-ray bursts

AXP/SGRDim thermal “Neutron” stars

Compact center objects

Members of the family of pulsars …

What’s really the nature of pulsars?

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

The nature of pulsars depends on physics of matter atThe nature of pulsars depends on physics of matter at supranuclearsupranuclear densitydensity which is still unknown! which is still unknown!

Pulsars

Normal neutron stars?

Quark stars? (strange or not)

Fluid?

Solid?

{{

Historical note on pulsars: Historical note on pulsars: SummarySummary

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

Still a challenging topic …to answer a question arising ~ 80 years ago!

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

Face-to-face … ones with big-names …

R. H. Fowler

S. Chandrasekhar

L. Landau

…

Summary

A historical note on pulsarsA historical note on pulsars

Obs. hints of quark stars?Obs. hints of quark stars?

ConclusionsConclusions

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

Observational hints of quark stars?SNE: bare quark star is better (Chen, Xu 2006)

Non-atomic features? e.g. RXJ1856 (Xu 2002, 2003)

(Bi)drifting subpulse: sparking (Xu…’99, Qiao…’04)

Radio & -ray profiles: annular gap (Qiao…’04a, …)

Glitches & slow-glitches: (Zhou… 2004, Xu 2006)

… (e.g., free-precessions, low-mass quark stars)

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

R. Buras, M. Rampp, H.-Th. Janka, K. Kifonidis, 2003, PRL90, 241101

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

Photon-driven supernovae?Photon-driven supernovae?The bare quark-surface helps supernovae?

-luminosity is not limited by the Eddington limit:

pEd 3dEdd

8

T

4g/s0 er1~

m cGMGMM ML

R M

2 4 2 4Thermal 6 11 Ed

5d

214 ~ 07 erg/sL R T R T L

Due to the chromatic confinement, the thermal luminosity on the quark surface could be as high as

Bare quark surface should be energetic source!

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

Photon-driven supernovae?Photon-driven supernovae?Model of photon-driven supernovae/GRBs

24

radiation 2

1( )

3

rP r aT

R

Low baryon contaminatio

n!

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

Nuclear

reaction

Non-atomic line in thermal emission

Why is the spectrum observation so important?

Red shift

Pressure broadening 2

/,

/

M RM R

M R

Observational competition: Who is

THE FIRST?

Sharp difference: Sharp difference: quark matter surfacequark matter surface!!

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

Observations: Featureless spectra!

Xu (2002)

Sharp difference: Sharp difference: quark matter surfacequark matter surface!!

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

Sharp difference: Sharp difference: quark matter surfacequark matter surface!!

NASA News release (2002/4/10): RX J1856 a strange star?

Chandra

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

Drifting subpulses in radio emission

PSR 0943+10 Deshpande & Rankin 1999

(Bi)drifting subpulse : (Bi)drifting subpulse : SparkingSparking!!

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

Ruderman-Sutherland (1975) modelVaccum-gap sparking Vd ~ c (EB/B2)RS requires: EB>~10keV & B<0

Difficulties in RS modelBounding energy of neutron stars: EB<10keVWhy haven’t we observe two distinct kinds of _pulsar radio emission (B<0, >0)?

Advantages of the bare strange star ideaEB for any Bkeeps the RS scenario of vacuum gap sparking“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

(Bi)drifting subpulse : (Bi)drifting subpulse : SparkingSparking!!

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

(Bi)drifting subpulse : (Bi)drifting subpulse : SparkingSparking!!

Qiao et al. 2004, ApJL

Bi-driftingBi-drifting

subpulsessubpulses

Summary

A historical note on pulsarsA historical note on pulsars

Obs. hints of quark stars?Obs. hints of quark stars?

ConclusionsConclusions

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

ConclusionsConclusions

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

Pulsars are not boring giant nuclei!

In addition to test GR, pulsars are also useful to test and to improve the fundamental strong interaction.

Possible evidence for quark stars are proposed.

A solid state of quark matter is suggested.

Thanks a lotand

Hope to receive your comment-suggestionAny time

Email: r.x.xu@pku.edu.cn

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu

Xu (COSPAR2004), 2006, Adv. in Space Research, 37, 1992 (astro-ph/0410652)

Wang et al. Nature 440 (2006) 772-775 (astro-ph/0604076)

“Pulsars and Quark Stars” http://vega.bac.pku.edu.cn/rxxu R. X. Xu