Fridolin Weber San Diego State University San Diego, California USA

Fridolin Weber San Diego State University San Diego, California USA IAU Symposium 291 Neutron Stars and Pulsars: Challenges and OpportuniEes afer 80 years IAU General Assembly XXVIII 20-31 August 2012, Beijing, China

Ø Strange Quark Stars versus Neutron Stars Ø Explore Testable Predic<ons q Rapid rotaeon q Ultra- high electric fields q OscillaEons of electron sea q Meissner effect (vortex expulsion) q Pycnonuclear reaceons Ø Summary

Strange Quark Star Neutron Star Surface Hydrogen/Helium plasma Iron nuclei Surface Outer Crust Ions Electron gas Outer Crust Inner Crust Heavy ions Relativistic electron gas Superfluid neutrons Outer Core Neutrons, protons Electrons, muons Core Electrons u,d,s quarks (color-superconducting) F. Weber (SDSU, 2012) I Radii < 10 km Masses ~1 to 2 M sun Radii > 10 km Inner Core Neutrons Superconducting protons Electrons, muons Hyperons (Σ, Λ, Ξ) Deltas (Δ) Boson (π, K) condensates Deconfined (u,d,s) quarks / colorsuperconducting quark matter

Quark Stars* vs Neutron Stars Ø Made enerely of deconfined quarks and leptons Ø Self- bound (M ~ R 3 ) Ø Baryon number O(1) < B < 10 57 Ø Electron sea at surface (super- high electric fields) Ø May posses outer crusts Ø No inner crusts Ø Two- parameter stellar sequences Ø May contain deconfined quark maaer only in stellar core Ø Bound by gravity Ø 10 56 to 10 57 Ø Absent Ø Outer crusts Ø Inner crusts Ø One- parameter stellar sequence *E. Wiaen, Phys. Rev. D 30 (1984) 272; Alcock, Farhi, Olinto, ApJ 310 (1986) 261; Alcock & Olinto, Ann. Rev. Nucl. Part. Sci. 38 (1988) 161; Madsen, Lecture Notes Phys. 516 (1999) 162.

M/M sun 10 1 10 0 10 1 10 2 10 3 Mass- radius relaeonship of neutron stars Black holes 1 Neutron stars void of compact stars 2 unstable equilibrium 3 configurations White dwarfs Planets 10 0 10 1 10 2 10 3 10 4 10 5 R (km)

Mass- radius relaeonship of neutron stars and strange quark stars d bc b a d b a b a

RotaEon at Sub- Millisecond Periods Kepler Period (msec) Observed masses and rotaeonal periods Neutron stars Strange quark stars

Electrically Charged Quark Stars Energy density of electric field is of same order as energy density of quark maaer! µ F kl F kl T µ =(P + )u u µ + P µ + 1 4 ideal fluid F µl F l + 1 4 GravitaEonal mass Increases by up to 15%. Radius increases by up to 5%. R. Negreiros, FW, M. Malheiro, V. Usov, PRD 80 (2009) 083006

Electrically Charged Quark Stars (cont.) Electron sphere may be differeneally rotaeng! I = ( + ) B = const E ( + )R Could explain observed magneec fields of CCOs R. Negreiros, I. Mishustin, S. Schramm, FW, PRD 82 (2010) 103010

Electron sea may perform global (hydrodynamical cyclotron) oscillaeons Frequency spectrum calculated by R. X. Xu et al.* *R. X. Xu, Bastrukov, FW, Yu, Molodtsova, PRD 85 (2012) 023008

AbsorpEon features in spectrum of 1E 1207.4-5209 at 0.7, 1.4 and 2.1 kev* 0.7 kev 1.4 kev 2.1 kev 0.5 1.0 2.0 *G. F. Bignami, P. A. Caraveo, A. De Luca, & S. Mereghen, Nature 423 (2003) 725

Meissner Effect in Quark Stars made of CFL Quark Maaer Vortex expulsion reheats the quark star

Cooling of CFL Quark Stars via Vortex Expulsion SGRs/AXPs Negreiros, Niebergal, Ouyed, FW, PRD 81 (2010) 043005

SGRs/AXPs Neutron stars Negreiros, Niebergal, Ouyed, FW, PRD 81 (2010) 043005

Pycnonuclear Reactions in the Crusts of Neutron Stars White dwarf Neutron star Neutron star crust Pycnonuclear reactions

Pycnonuclear Reactions in the Crusts of Neutron Stars White dwarf Neutron star Strange quark matter nuggets embedded in the nuclear crust

Strange Quark Matter Nuggets l N u ~ N d ~ N s l A > A min (~10 to 100) l Charge-to-baryon number ratio depends on whether SQM is made of Ø ordinary quark matter, Z 0.1 (m 150 ) 2 A, or Ø color superconducting quark matter, Z 0.3 m 150 A 2/3 Farhi & Jaffe, PRD 30 (1984) 2379; Berger & Jaffe, PRC 35 (1987) 213; Alcock, Farhi, Olinto, ApJ 310 (1986) 261; Madsen, PRL 87 (2001) 172003 Madsen, PRL 87 (2001) 172003; Rajagopal & Wilczek, PRL 86 (2001) 3492; Oertel & Urban PRD 77 (2008) 074015

R = (lattice pairs) x T Coulomb barrier x S x E -1 ) " #!! "#$% " &% '( & # * $ * * & $ * % $ &% & +'' ' (*#("(')& ( (& # & # # *!"#!$%&'()* +"#,-,'(*.'#'/&*0, 1"#2&33#4526,* 7"#2&33#8,43.(9 :"#.4;,*3,#-,40(/#<&*&2,(,* Gasques et al. PRC 72 (2005) 025806! Yakovlev et al. PRC 74 (2006) 035803! 6)89#',4(,*,8#'56.'#=6''>#-&((.',

Impact of quark maaer nuggets on pycnonuclear reaceon rates B. Golf, J. Hellmers, F. Weber, PRC 80 (2009) 015804

q True ground state of the strong interaceon is not known q Key differences between neutron stars and quark stars emerge from the fact that quark stars are self- bound and possess electron seas at their surfaces. q Peculiar stellar properees/phenomena to watch out for: superfast rotaeon, unusually small objects (CCOs), unusually hot objects (SGRs, AGRs), absorpeon features (XDIN, CCOs), superbursts, drifing sub- pulses (R. X. Xu), quark novae (R. Ouyed),...? q Need more observed data (e.g. SkA, FAST)