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Post Info TOPIC: PSR J1614-2230
Blobrana


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Title: Existence of hyperons in the pulsar PSRJ1614-2230
Authors: A. Sulaksono, B. K. Agrawal

The possibility of existence of hyperons in the recently measured 2 solar mass pulsar PSRJ1614-2230 is explored using a diverse set of nuclear equations of state calculated within the relativistic mean-field models. Our results indicate that the nuclear equations of state compatible with heavy-ion data allow the hyperons to exist in the PSRJ1614-2230 only for significantly larger values for the meson-hyperon coupling strengths. The maximum mass configurations for these cases contain sizable hyperon fractions (\sim 60%) and yet masquerade their counterpart composed of only nucleonic matter.

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Blobrana


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Title: Mixed phase in a compact star with strong magnetic field
Authors: Ritam Mallick, P. K. Sahu

Compact stars can have either hadronic matter or can have exotic states of matter like strange quark matter or colour superconducting matter. Stars also can have a quark core surrounded by hadronic matter, known as hybrid stars (HS). The HS is likely to have a mixed phase in between the hadron and quark phase. Observational results suggest huge surface magnetic field in certain neutron stars (NS) called magnetars. Here we study the effect of strong magnetic field on the respective EOS of matter under extreme conditions. We further study the hadron-quark phase transition in the interiors of NS giving rise to hybrid stars (HS) in presence of strong magnetic field. The hadronic matter EOS is described based on relativistic mean field theory and we include the effect of strong magnetic fields leading to Landau quantisation of the charged particles. For the quark phase we use the simple MIT bag model. We assume density dependent bag pressure and magnetic field. The magnetic field strength increases going from the surface to the center of the star. We construct the intermediate mixed phase using Glendenning conjecture. The magnetic field softens the EOS of both the matter phases. The effect of magnetic field is insignificant unless the field strength is above 10^{14}G. A varying magnetic field, with surface field strength of 10^{14}G and the central field strength of the order of 10^{17}G has significant effect on both the stiffness and the mixed phase regime of the EOS. We finally study the mass-radius relationship for such type of mixed HS, calculating their maximum mass, and compare them with the recent observation of pulsar PSR J1614-2230, which is about 2 solar mass. The observations puts a severe constraint on the EOS of matter at extreme conditions. The maximum mass with our EOS can reach the limit set by the observation.

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Blobrana


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Title: Maximum mass of a hybrid star having a mixed phase region in the light of pulsar PSR J1614-2230
Authors: Ritam Mallick

Recent observation of pulsar PSR J1614-2230 with mass about 2 solar masses poses a severe constraint on the equations of state (EOS) of matter describing stars under extreme conditions. Neutron stars (NS) can reach the mass limits set by PSR J1614-2230. But stars having hyperons or quark stars (QS) having boson condensates, with softer EOS can barely reach such limits and are ruled out. QS with pure strange matter also cannot have such high mass unless the effect of strong coupling constant or colour superconductivity are taken into account. In this work I try to calculate the upper mass limit for a hybrid stars (HS) having a quark-hadron mixed phase. The hadronic matter (having hyperons) EOS is described by relativistic mean field theory and for the quark phase I use the simple MIT bag model. I construct the intermediate mixed phase using Glendenning construction. HS with a mixed phase cannot reach the mass limit set by PSR J1614-2230 unless I assume a density dependent bag constant. For such case the mixed phase region is small. The maximum mass of a mixed hybrid star obtained with such mixed phase region is 2.01 solar masses.

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Blobrana


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PSR J 1614-2230
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Title: Is the high mass binary pulsar PSR J 1614-2230 a latent magnetar?
Authors: Vikram Soni

We consider the newly found high mass and low magnetic field binary pulsar PSR J1614-2230 in a model in which magnetars owe their strong magnetic fields to a high baryon density, magnetized core. In our magnetar model all neutron stars above a certain threshold mass are magnetars. This confronts us with the very basic paradox as to why this high mass star, PSR J1614-2230, remains a pulsar and shows no magnetar characteristics. This is a star that has acquired its large mass by accretion from its binary companion over 5 gigayears.
In this work we show that the maximum rate of energy gain from the strong interaction phase transition from this slow accretion does not allow for high enough interior temperature for ambipolar transport of the magnetic field to the surface of the star and thus the PSR J 1614-2230 remains latent and does not become an emergent magnetar.

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Blobrana


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Title: The White Dwarf Companion of a 2 solar mass Neutron Star
Authors: Varun B. Bhalerao, S. R. Kulkarni

We report the optical discovery of the companion to the 2 solar mass millisecond pulsar PSR J1614-2230. The optical colours show that the 0.5 solar mass companion is a 2.2 Gyr old He-CO white dwarf. We infer that \dot{M} during the accretion phase is <10^{-2} \dot{M}_{edd}. We show that the pulsar was born with a spin close to its current value, well below the rebirth line. The spin-down parameters, the mass of the pulsar, and the age of the system challenge the simple recycling model for the formation of millisecond pulsars.

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Blobrana


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Astronomers have discovered what they say is the heaviest neutron star yet.
The super-dense object, which lies some 3,000 light-years from Earth, is about twice as massive as our Sun.
That is 20% greater than the previous record holder, the US-Dutch team behind the observation tells the journal Nature.
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An extremely dense celestial object thousands of light-years away is serving as a natural nuclear physics experiment, providing clues to processes that cannot be reproduced in the lab.
Astrophysicists look to neutron stars, extraordinarily compact remnants of massive stars, to find out how matter behaves at the highest densities that it can withstand.
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Blobrana


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The largest pulsating star yet observed casts doubts on exotic-matter theories.

Neutron stars are living up to their name. Measurements of radio waves emanating from the most massive pulsating star yet discovered suggest that it is, indeed, made up of neutrons, rather than exotic particles, as some theories propose.
Neutron stars are the corpses left behind after certain normal stars explode as supernovae. According to standard astronomical models, matter is squeezed down so tightly within their cores that nuclei break apart into their constituents, with protons and electrons crushed together into neutrons - hence the stars' name.
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