Effects of color superconductivity on the structure and formation of compact stars (original) (raw)

Color Superconductivity in Compact Stars and Gamma Ray Bursts

AIP Conference Proceedings, 2004

We study the effects of color superconductivity on the structure and formation of compact stars. We show that it is possible to satisfy most of recent observational boundaries on masses and radii if a diquark condensate forms in a hybrid or a quark star. Moreover, we find that a huge amount of energy, of the order of 10 53 erg, can be released in the conversion from a (metastable) hadronic star into a (stable) hybrid or quark star, if the presence of a color superconducting phase is taken into account. Accordingly to the scenario proposed in Astrophys.J.586(2003)1250, the energy released in this conversion can power a Gamma Ray Burst. This mechanism can explain the recent observations indicating a delay, of the order of days or years, between a few Supernova explosions and the subsequent Gamma Ray Burst.

Effects of quark matter and color superconductivity in compact stars

2003

The equation of state for quark matter is derived for a nonlocal, chiral quark model within the mean field approximation. We investigate the effects of a variation of the form factors of the interaction on the phase diagram of quark matter under the condition of β -equilibrium and charge neutrality. Special emphasis is on the occurrence of a diquark condensate which signals a phase transition to color superconductivity and its effects on the equation of state. We calculate the quark star configurations by solving the Tolman-Oppenheimer-Volkoff equations and obtain for the transition from a hot, normal quark matter core of a protoneutron star to a cool diquark condensed one a release of binding energy of the order of ∆Mc 2 ∼ 10 53 erg. We study the consequences of antineutrino trapping in hot quark matter for quark star configurations with possible diquark condensation and discuss the claim that this energy could serve as an engine for explosive phenomena. A "phase diagram" for rotating compact stars (angular velocity-baryon mass plane) is suggested as a heuristic tool for obtaining constraints on the equation of state of QCD at high densities. It has a critical line dividing hadronic from quark core stars which is correlated with a local maximum of the moment of inertia and can thus be subject to experimental verification by observation of the rotational behavior of accreting compact stars.

Supernovae, hypernovae and color superconductivity

Physics Letters B, 2001

We argue that color superconductivity (CSC, Cooper pairing in quark matter leading to the breaking of SU(3) color symmetry) may play a role in triggering the explosive endpoint of stellar evolution in massive stars (M > 8M ). We show that the binding energy release in the transition of a subcore region to the CSC phase can be of the same order of magnitude as the gravitational binding energy release from core collapse. The core temperature during collapse is likely below the critical temperature for CSC, and the transition is first order, proceeding on Fermi timescales when the pressure reaches a critical value of several times nuclear density. We also discuss the implications for hypernova events with total ejecta energy of 10-100 times that of type II supernova.  2001 Elsevier Science B.V. All rights reserved. 0370-2693/01/$ -see front matter  2001 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 0 -2 6 9 3 ( 0 1 ) 0 0 9 5 5 -8

Color Superconducting Quark Matter in Compact Stars

Exotic States Of Nuclear Matter, 2008

Recent indications for high neutron star masses (M ∼ 2 M ⊙) and large radii (R > 12 km) could rule out soft equations of state and have provoked a debate whether the occurence of quark matter in compact stars can be excluded as well. We show that modern quantum field theoretical approaches to quark matter including color superconductivity and a vector meanfield allow a microscopic description of hybrid stars which fulfill the new, strong constraints. For these objects color superconductivity turns out to be an essential ingredient for a successful description of the cooling phenomenology in accordance with recently developed tests. We discuss the energy release in the neutrino untrapping transition as a new aspect of the problem that hybrid stars masquerade themselves as neutron stars. Quark matter searches in future generations of low-temperature/high-density nucleus-nucleus collision experiments such as low-energy RHIC and CBM @ FAIR might face the same problem of an almost crossover behavior of the deconfinement transition. Therefore, diagnostic tools shall be derived fromeffects of color superconductivity.

Structure of compact stars with color superconductivity quark phase

Nuclear Physics B-proceedings Supplements, 2005

We study the effects of color superconductivity on the structure of compact stars, and we show that it is possible to satisfy most of recent observational boundaries on masses and radii if a diquark condensate forms in a hybrid or in a quark star. Furthermore, we find that the constraints on masses and radii of the compact stellar objects put

Composition and stability of hybrid stars with hyperons and quark color-superconductivity

Astronomy & Astrophysics, 2012

The recent measurement of a 1.97 ± 0.04 solar-mass pulsar places a stringent lower bound on the maximum mass of compact stars and therefore challenges the existence of any agents that soften the equation of state of ultra-dense matter. We investigate whether hyperons and/or quark matter can be accommodated in massive compact stars by constructing an equation of state based on a combination of phenomenological relativistic hyper-nuclear density functional and an effective model of quantum chromodynamics (the Nambu-Jona-Lasinio model). Stable configurations are obtained with M ≥ 1.97 M ⊙ featuring hyper-nuclear and quark matter in color superconducting state if the equation of state of nuclear matter is stiff above the saturation density, the transition to quark matter takes place at a few times the nuclear saturation density, and the repulsive vector interactions in quark matter are substantial.

Effects of color superconductivity on the nucleation of quark matter in neutron stars

Astronomy and Astrophysics, 2007

Aims. We study the nucleation of quark matter drops at the center of cold deleptonized neutron stars. These drops can be made up by unpaired quark matter or by color superconducting quark matter, depending on the details of the equations of state for quark and hadronic matter. The nature of the nucleated phase is relevant in the determination of the critical mass Mcr of hadronic stars above which it is possible a transition to a quark star (strange or hybrid). Methods. We investigate the dependence of Mcr upon the parameters of the quark model (the Bag constant B, the pairing gap ∆, and the surface tension σ of the quark-hadron interface) and for different parametrizations of the hadronic equation of state. We also calculate the energy released in the conversion of a pure hadronic star having the critical mass into a quark star. Results. In general, the dependence of Mcr on B, ∆ and σ is mild if the parameters of the quark model correspond to hybrid stars, and strong if they correspond to strange stars. Also, the critical mass always decreases with ∆, and increases with B and σ. The total released energy is in the range 3 × 10 52 erg-4 × 10 53 erg. Conclusions. For a large part of the parameter space corresponding to hybrid stars, the critical mass is very close (but smaller than) the maximum mass of hadronic stars, and therefore compatible with a "mixed" population of compact stars (pure hadronic up to the critical mass and hybrid above the critical mass). For very large B the critical mass is never smaller than the maximum mass of hadronic stars, implying that quark stars cannot form through the here studied mechanism. The energy released in the conversion is sufficient to power a gamma ray burst.

Structure and cooling of compact stars with color superconductivity

29Th Johns Hopkins Workshop on Current Problems in Particle Theory Strong Matter in the Heavens, 2006

We review the status of research on the cooling of compact stars with special emphasis on possible color superconducting quark matter phases in the stars interior. Although a consistent microscopic approach is not yet available severe constraints for the phase structure of compact star matter at high densities come from recent mass and cooling observations.

Implications of Two-Flavour Colour Superconductivity on Compact Star Physics

2007

In this thesis, we study the thermodynamics of two-flavour colour superconductivity and the effects of its occurrence on the structure and cooling of compact stars. We consider pure two-flavour colour superconductors (2SC), gapless 2SC (g2SC), mixed phase of non-superconducting (normal) quark matter and 2SC or g2SC phase, with possibly free strange quarks present. We employ the BCS pairing interaction through a four-quark operator with the quantum numbers of a single gluon exchange. Low density matter on the crust of the star is modeled by the neutral hadronic phase in the relativistic mean field approximation. The equations of state of the quark and the hadronic phases are found, as well as the phase diagram of the quark matter. The quark matter is seen to undergo second order phase transitions from the mixed phase to pure 2SC or g2SC phase and in between the 2SC and g2SC phases. The quark matter also undergoes a second order phase transition from normal to pure colour superconducting phase with increase of the baryon chemical potential. The mass and structure of the stars are found by solving the Tolman-Oppenheimer-Volkoff equations together with the equation of state of the particular phase. We find a transition from pure quark to hybrid and ultimately pure hadronic stars with increase of bag constant. For certain bag constants, with increase of central pressure, we see an unstable branch in the mass versus radius plot of the hybrid stars which later changes into a stable branch. We find the difference of mass and total baryon number between configurations of the compact stars at zero and finite central temperatures as functions of the central pressure. The cooling stars are considered at fixed total baryon number. We find the thermal capacity or the ratio of the energy lost to the change of central temperature for quark stars with the colour superconducting or normal quark phase. The quark stars without free strange quarks in 2SC phase loose more energy while cooling compared to stars with non-zero strangeness. The cooling quark stars however shrink more if they contain free strange quarks. 1 Introduction 1 1.1 Physical Overview 1 1.2 Thesis Outline 4 2 Phases of Quantum Chromodynamics within Compact Stars 6 2.1 The QCD Lagrangian and its Symmetries 7 2.2 Nuclear Matter Phase of QCD 2.2.1 Hadronic Composition of Neutron Stars 2.2.2 Effective Field Theoretical Model of Neutron Star Matter 2.2.3 The Mean Field Approximation 2.3 Colour Superconductivity of Quark Matter 2.4 The 2SC Phase 2.4.1 The 2SC Lagrangian Density 2.4.2 The Chemical Potentials of the Quarks 2.4.3 Dispersion Relation and Partition Function of the 2SC Phase 2.5 The Gapless 2SC Phase 3 Thermodynamics of QCD Phases 3.1 Thermodynamics of Normal Quark Matter 3.2 Thermodynamics of Hadronic Phase 41 3.3 Thermodynamics of Two-Flavour Colour Superconductors. . 4 Compact Stars with Colour Superconducting Cores .... 83 4.1 The Tolman-Oppenheimer-Volkoff Equations for Stellar Structure 83 4.1.1 Equation of State of Stellar Matter 85 4.2 Solution of TOV Equations 4.2.1 Scaled TOV Equations 90 4.3 Mass and Radius of Cold Compact Stars with Colour Superconducting Matter 91 4.3.1 Mass and Radius of Hybrid Stars Table of Contents 4.4 Temperature Dependence of Compact Star Structure 97 4.4.1 Hot Quark Stars 98 4.4.2 Binding Energy of Quark Stars 100 4.4.3 Change of Mass, Radius and Total Baryon Number of Quark Stars with Temperature 102 4.4.4 Error in the Determination of Radius, Mass and Total Baryon Number of Compact Stars 122 4.4.5 Hot Hybrid and Hadronic Stars 4.4.6 Change of Mass, Radius and Total Baryon Number of Hybrid and Hadronic Stars with Temperature 5 Cooling of Quark Stars 5.1 Compact Stars with and. without Trapped Neutrinos 130 5.2 Cooling of Quark Stars 5.2.1 Cooling of Quark Star with 2SC Phase and Free Strange Quarks 5.2.2 Cooling of Quark Star with Two Flavours

Color superconducting quark matter core in the third family of compact stars

Physical Review D, 2003

We investigate first order phase transitions from β-equilibrated hadronic matter to color flavor locked quark matter in compact star interior. The hadronic phase including hyperons and Bose-Einstein condensate of K − mesons is described by the relativistic field theoretical model with density dependent meson-baryon couplings. The early appearance of hyperons and/or Bose-Einstein condensate of K − mesons delays the onset of phase transition to higher density. In the presence of hyperons and/or K − condensate, the overall equations of state become softer resulting in smaller maximum masses than the cases without hyperons and K − condensate. We find that the maximum mass neutron stars may contain a mixed phase core of hyperons, K − condensate and color superconducting quark matter. Depending on the parameter space, we also observe that there is a stable branch of superdense stars called the third family branch beyond the neutron star branch. Compact stars in the third family branch may contain pure color superconducting core and have radii smaller than those of the neutron star branch. Our results are compared with the recent observations on RX J185635-3754 and the recently measured mass-radius relationship by X-ray Multi Mirror-Newton Observatory.