ΛΣ− PAIRING IN “BUBBLE FERMI SHELL” SCHEME

2008 ◽  
Vol 23 (27n30) ◽  
pp. 2473-2476 ◽  
Author(s):  
TATSUYUKI TAKATSUKA ◽  
RYOZO TAMAGAKI
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Superfluid State ◽  
Fermi Surfaces ◽  
Realistic Approach

In neutron star cores, superfluid state of hyperons such as lambda (Λ) and sigma-minus (Σ−) has been shown to realize by a realistic approach. This result importantly supports the idea of nonstandard fast “hyperon cooling” scenario to explain colder class neutron stars observed. However, a less attractive ΛΛ interaction suggested by a double Λ hypernucleus ([Formula: see text]; “NAGARA” event) leads to a disappearance of Λ superfluidity and thereby the breaking down of the scenario. In this connection, the revival of “Λ superfluidity” due to the ΛΣ− pairing, instead of ΛΛ one, is discussed in a new scheme of “bubble Fermi shell” hypothesis where the matching of two different Fermi surfaces is forced.

EFFECTS OF HYPERON MIXING ON NEUTRON STAR PROPERTIES

2008 ◽  
Vol 17 (09) ◽  
pp. 1739-1752
Author(s):  
TATSUYUKI TAKATSUKA
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Quark Model ◽  
Body Force ◽  
String Junction ◽  
Promising Candidate ◽  
Fermi Surfaces ◽  
Realistic Approach ◽  
Three Body

From a serious inconsistency between theory and observations for the mass of hyperon-mixed neutron stars (NSs), it is stressed that some "extra repulsion" is missing in hypernuclear systems and three-body force repulsion is tested for the cases with phenomenological Illinoi's type, 2π-exchange via Δ-excitation type(2πΔ) and string-junction quark model(SJM). It is remarked that the "extra repulsion" should have a nature to act universally, i.e., independent of baryon species. The SJM three-body repulsion can meet the condition because of flavor-independence and {2πΔ+ SJM } scheme is shown to be a promising candidate for the "extra repulsion". Occurence of Λ and Σ- superfluidities are shown also by a realistic approach, which importantly supports the idea of nonstandard fast "hyperon cooling" scenario to explain colder class NSs. However, less attractive ΛΛ interaction suggested by the "NAGARA event" [Formula: see text] leads to the disappearance of Λ superfluidity and the breaking down of the scenario. In this connection, the revival of "Λ superfluidity" due to ΛΣ- pairing instead of ΛΛ one is discussed in a new scheme of "bubble shell" hypothesis where the matching of two different Fermi surfaces is forced.

scholarly journals A Gravitational-Wave Perspective on Neutron-Star Seismology

Universe ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 97
Author(s):  
Nils Andersson
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Gravitational Wave ◽  
Fundamental Mode ◽  
Compact Binaries

We provide a bird’s-eye view of neutron-star seismology, which aims to probe the extreme physics associated with these objects, in the context of gravitational-wave astronomy. Focussing on the fundamental mode of oscillation, which is an efficient gravitational-wave emitter, we consider the seismology aspects of a number of astrophysically relevant scenarios, ranging from transients (like pulsar glitches and magnetar flares), to the dynamics of tides in inspiralling compact binaries and the eventual merged object and instabilities acting in isolated, rapidly rotating, neutron stars. The aim is not to provide a thorough review, but rather to introduce (some of) the key ideas and highlight issues that need further attention.

Aspects of the Collapse of Compact Objects

1980 ◽  
Vol 4 (1) ◽  
pp. 49-50
Author(s):  
R. A. Gingold ◽  
J. J. Monaghan
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
White Dwarf ◽  
Compact Objects ◽  
Dwarf Star

Misner Thorne and Wheeler (1973), (page 629) suggested that a freshly formed White Dwarf star of several solar masses would, if slowly — rotating, collapse to form a neutron star pancake which would become unstable and eventually produce several, possibly colliding, neutron stars.

scholarly journals Remnant massive neutron stars of binary neutron star mergers: Evolution process and gravitational waveform

2013 ◽  
Vol 88 (4) ◽  
Author(s):  
Kenta Hotokezaka ◽  
Kenta Kiuchi ◽  
Koutarou Kyutoku ◽  
Takayuki Muranushi ◽  
Yu-ichiro Sekiguchi ◽  
...  
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Evolution Process ◽  
Binary Neutron Star

scholarly journals Nuclear equation of state and neutron star cooling

2017 ◽  
Vol 26 (04) ◽  
pp. 1750015 ◽  
Author(s):  
Yeunhwan Lim ◽  
Chang Ho Hyun ◽  
Chang-Hwan Lee
Keyword(s):  
Neutron Star ◽  
Equation Of State ◽  
Neutron Stars ◽  
Nuclear Matter ◽  
Thermal Evolution ◽  
Observation Data ◽  
Nuclear Equation Of State ◽  
The Core ◽  
Dense Nuclear Matter ◽  
Nuclear Models

In this paper, we investigate the cooling of neutron stars with relativistic and nonrelativistic models of dense nuclear matter. We focus on the effects of uncertainties originated from the nuclear models, the composition of elements in the envelope region, and the formation of superfluidity in the core and the crust of neutron stars. Discovery of [Formula: see text] neutron stars PSR J1614−2230 and PSR J0343[Formula: see text]0432 has triggered the revival of stiff nuclear equation of state at high densities. In the meantime, observation of a neutron star in Cassiopeia A for more than 10 years has provided us with very accurate data for the thermal evolution of neutron stars. Both mass and temperature of neutron stars depend critically on the equation of state of nuclear matter, so we first search for nuclear models that satisfy the constraints from mass and temperature simultaneously within a reasonable range. With selected models, we explore the effects of element composition in the envelope region, and the existence of superfluidity in the core and the crust of neutron stars. Due to uncertainty in the composition of particles in the envelope region, we obtain a range of cooling curves that can cover substantial region of observation data.

DO YOUNG NEUTRON STARS WHICH SHOW THEMSELVES AS AXPs AND SGRs ACCRETE?

2003 ◽  
Vol 12 (05) ◽  
pp. 825-831 ◽  
Author(s):  
S. O. TAGIEVA ◽  
E. YAZGAN ◽  
A. ANKAY
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Supernova Explosion ◽  
X Ray ◽  
X Ray Binaries

We examined the fall-back disk models, and in general accretion, proposed to explain the properties of AXPs and SGRs. We checked the possibility of some gas remaining around the neutron star after a supernova explosion. We also compared AXPs and SGRs with the X-ray pulsars in X-ray binaries. We conclude that the existing models of accretion from a fall-back disk are insufficient to explain the nature of AXPs and SGRs.

scholarly journals Quadrupole moments of rotating compact stars

2012 ◽  
Vol 8 (S291) ◽  
pp. 536-536
Author(s):  
Martin Urbanec ◽  
John Miller ◽  
Zdenek Stuchlik
Keyword(s):  
Neutron Star ◽  
Equation Of State ◽  
Neutron Stars ◽  
Strange Star ◽  
Compact Stars ◽  
Quadrupole Moments ◽  
Strange Stars

AbstractWe present quadrupole moments of rotating neutron and strange stars calculated using standard Hartle Thorne approach. We demonstrate differences between neutron and strange star parameters connected with quadrupole moments and how this parameters could be, in the case of neutron stars, approximated almost independently on neutron star equation of state.

scholarly journals 1S0 Pairing Gaps, Chemical Potentials and Entrainment Matrix in Superfluid Neutron-Star Cores for the Brussels–Montreal Functionals

Universe ◽  
2021 ◽  
Vol 7 (12) ◽  
pp. 470
Author(s):  
Valentin Allard ◽  
Nicolas Chamel
Keyword(s):  
Neutron Star ◽  
Equation Of State ◽  
Neutron Stars ◽  
Physical Meaning ◽  
Outer Core ◽  
Time Dependent ◽  
Hartree Fock ◽  
Chemical Potentials ◽  
Bogoliubov Equations ◽  
Flow Velocities

Temperature and velocity-dependent 1S0 pairing gaps, chemical potentials and entrainment matrix in dense homogeneous neutron–proton superfluid mixtures constituting the outer core of neutron stars, are determined fully self-consistently by solving numerically the time-dependent Hartree–Fock–Bogoliubov equations over the whole range of temperatures and flow velocities for which superfluidity can exist. Calculations have been made for npeμ in beta-equilibrium using the Brussels–Montreal functional BSk24. The accuracy of various approximations is assessed and the physical meaning of the different velocities and momentum densities appearing in the theory is clarified. Together with the unified equation of state published earlier, the present results provide consistent microscopic inputs for modeling superfluid neutron-star cores.

LIGO/Virgo Listens to Neutron Stars

2020 ◽  
pp. 137-145
Author(s):  
John W. Moffat
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Gravitational Waves ◽  
Gamma Ray ◽  
Accurate Determination ◽  
Hubble Constant ◽  
Gravitational Theory ◽  
Optical Signal ◽  
Gravity Models ◽  
Expansion Of The Universe

On August 8, 2017, LIGO/Virgo detected the merging of two neutron stars 130 million light years away. Just 1.7 seconds later, the Fermi Gamma Ray Space Telescope received an optical signal—a short gamma ray burst (GRB). Thus began a new era of “multimessenger astronomy.” The GRBs are very energetic explosions observed in galaxies. The neutron star merger offers the first evidence that heavy metals such as gold, platinum, and uranium were created by the collision of neutron stars in a “kilonova.” The resulting gravitational waves offer a new way of measuring the Hubble constant, which determines the rate of expansion of the universe. An important result from the neutron star merger is an extremely accurate determination of the speed of gravitational waves; they move at the speed of light. This has significant ramifications for gravitational theory. It falsifies many proposed modified gravity models.

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