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In this article, we study the neutron stars with antikaon condensates and their radial oscillations. We incorporate the antikaons (K - , K ¯ 0) within a relativistic mean field theory with density dependent couplings. A transition to the kaon condensed phase is treated as a second order phase transition for different possible antikaon optical potentials. Then, we solve the structure equations of stars and calculate the fundamental and higher order frequencies of their radial pulsations. We study the eigenfunctions of different radial modes for a 2 M ⊙ star with equations of state having different potential depths of antikaons. We also study the large frequency separations for the 2 M ⊙ star. We find distinct features of the appearances of antikaons on the eigenfunctions. The shape of the eigenfunctions corresponding to the radial perturbations is affected due to the appearance of the antikaons, but for the pressure perturbation, the shape remains unchanged. [ABSTRACT FROM AUTHOR]

We show that the odds of the mass-gap (secondary) object in GW190814 being a neutron star (NS) improve if one allows for a stiff high-density equation of state (EoS) or a large spin. Since its mass is |$\in (2.50,2.67) \, \mathrm{M}_{\odot }$|⁠ , establishing its true nature will make it either the heaviest NS or the lightest black hole (BH), and can have far-reaching implications on NS EoS and compact object formation channels. When limiting oneself to the NS hypothesis, we deduce the secondary's properties by using a Bayesian framework with a hybrid EoS formulation that employs a parabolic expansion-based nuclear empirical parametrization around the nuclear saturation density augmented by a generic 3-segment piecewise polytrope (PP) model at higher densities and combining a variety of astrophysical observations. For the slow-rotation scenario, GW190814 implies a very stiff EoS and a stringent constraint on the EoS specially in the high-density region. On the other hand assuming the secondary object is a rapidly rotating NS, we constrain its rotational frequency to be |$f=1170^{+389}_{-495}$| Hz, within a 90 per cent confidence interval (CI). In this scenario, the secondary object in GW190814 would qualify as the fastest rotating NS ever observed. However, for this scenario to be viable, rotational instabilities would have to be suppressed both during formation and the subsequent evolution until merger, otherwise the secondary of GW190814 is more likely to be a BH. [ABSTRACT FROM AUTHOR]

In this work, we compare two powerful parameter estimation methods, namely Bayesian inference and neural network based learning, to study the quark matter equation of state with constant speed of sound parameterization and the structure of the quark stars within the two-family scenario. We use the mass and radius estimations from several X-ray sources and also the mass and tidal deformability measurements from gravitational wave events to constrain the parameters of our model. The results found from the two methods are consistent. The predicted speed of sound is compatible with the conformal limit. [ABSTRACT FROM AUTHOR]

We present a Bayesian analysis to constrain the equation of state of dense nucleonic matter by exploiting the available data from symmetric nuclear matter at saturation, observations of compact X-ray sources, and the gravitational wave event GW170817. For the first time, such an analysis is performed by using a class of models, the relativistic mean field models, that allow one to consistently construct an equation of state in a wide range of densities, isospin asymmetries, and temperatures. The selected class of models contains five nuclear physics empirical parameters at saturation for which we construct the joint posterior distributions. By exploring different types of priors, we find that the equations of state with the largest evidence are the ones featuring a strong reduction of the effective mass of the nucleons in dense matter, which can be interpreted as an indication of a phase transition to a chiral symmetry restored phase. Those equations of state, in turn, predict R1.4 ∼ 12 km. Finally, we present a preliminary investigation of the effect of including Λ hyperons, showing that they appear in stars more massive than about 1.6 M⊙ and lead to radii larger than about R1.4 ∼ 14 km. Within the model explored here, the formation of such particles provides poor agreement with the constraints from GW170817. [ABSTRACT FROM AUTHOR]

The abrupt change in the pulse period of a pulsar is called a pulsar glitch. In this paper, we present 11 pulsar glitches detected using the Ooty Radio Telescope (ORT) and the upgraded Giant Metrewave Radio Telescope (uGMRT) in high cadence timing observations of 8 pulsars. The measured relative amplitude of glitches (Δ ν / ν) from our data ranges from 10−6 to 10−9. Among these glitches, three are new discoveries, being reported for the first time. We also reanalyse the largest pulsar glitch in the Crab pulsar (PSR J0534+2200) by fitting the ORT data to a new phenomenological model including the slow rise in the post-glitch evolution. We measure an exponential recovery of 30 d after the Vela glitch detected on MJD 57734 with a healing factor Q  = 5.8 × 10−3. Further, we report the largest glitch (Δ ν / ν  = 3147.9 × 10−9) so far in PSR J1731−4744. [ABSTRACT FROM AUTHOR]

In this work, we study the properties and structure of a massive and rapidly rotating protoneutron star (PNS) with hyperon content. We follow several stages of quasi-stationary evolution in an approximate way at four discrete steps. We use a density-dependent relativistic mean field theory model and calculate different quantities such as mass, equatorial radius, moment of inertia, and quadrupole moment to get different rotating configurations up to the mass-shedding limit. We study the effect of the appearance of Λ, the lightest of all hyperons, on each of the evolutionary stages of the PNS. We also check its sensitivity to the inclusion of ϕ vector meson as a mediator of Λ–Λ interaction in detail. Finally, we investigate the universal relations between moment of inertia and compactness in the context of a hot and young compact object. [ABSTRACT FROM AUTHOR]

We investigate the impact of strange-matter equations of state involving Λ hyperons, Bose-Einstein condensate of K- mesons and first-order hadron-quark phase transition on moment of inertia, quadrupole moment and tidal deformability parameter of slowly rotating neutron stars. All these equations of state are compatible with the 2 Msolar constraint. The main findings of this investigation are the universality of the I-Q and I-Love number relations, which are preserved by the EoSs including Λ hyperons and antikaon condensates, but broken in the presence of a first-order hadron-quark phase transition. Furthermore, it is also noted that the quadrupole moment approaches the Kerr value of a black hole for maximum-mass neutron stars. [ABSTRACT FROM AUTHOR]

We calculate moment of inertia of neutron star with different exotic constituents such as hyperons and antikaon condensates and study its variation with mass and spin frequency. The sets of equation-of-state (EoS), generated within the framework of relativistic mean field model with density-dependent couplings are adopted for the purpose. We follow the quasi-stationary evolution of rotating stars along the constant rest mass sequences, that varies considerably with different constituents in the EoS. We also explore the universal relations associated with some of the normalized properties, such as critical mass and moment of inertia for specific EoS or as a matter of fact constituents of the dense matter. Deviations in the universal relations for moment of inertia are observed at higher compactness. This study presents important results concerning the properties of neutron stars, that could be observationally verified in the near future using Square Kilometer Array telescope. [ABSTRACT FROM AUTHOR]