In this study, we develop an iterative method for computing both rigidly and differentially rotating polytropic models in critical rotation. We work in the framework of post-Newtonian theory in order to simulate fully relativistic rotating neutron stars. Our method results as combination of three methods: the "Hybrid Approximative Scheme" (HAS), the "Complex-plane Iterative Technique" (CIT),...
A deep exploration of the parameter space that relates the interacting equation of state with the bag constant B, and the interaction parameter a, is fundamental for the construction of diverse models of quark stars. In particular, the anisotropy of quark stars with a well motivated quantum chromodynamics (QCD) equation of state is presented here. The contribution of the fourth order...
We study bulk viscosity arising from weak interaction processes in dense baryonic matter for temperature-density range relevant to neutron star mergers. We consider two compositions of baryonic matter: a) pure nucleonic matter, where the main source of bulk viscosity are weak current direct Urca processes – neutron decay and electron capture; b) hypernuclear matter, where the bulk viscosity...
In Castillo et al. (2017}, the first simulations of ambipolar diffusion in a spherical neutron star cores were reported, contributing to the understanding of the long-term evolution of their magnetic fields. In that work the NS interior is modeled as a charged-particle fluid of npe-matter, with a uniform and motionless background of neutrons that exerts a collisional drag force on the former....
The external Hartle-Thorne geometry, which describes the spacetime outside a slowly rotating compact star, is characterised by the gravitational mass M, angular momentum J, and quadrupole moment Q of the star and gives a convenient description, which, for the rotation frequencies of more than 95% of known pulsars, is sufficiently accurate for most purposes. Our investigation is motivated by...
The magnetospheres of compact objects are complex systems, that comprise kinetic-scale pair plasma physics, quantum electrodynamics (QED) processes, and general relativity (GR). To study such rich systems, advanced simulation techniques are required. Combining traditional particle-in-cell (PIC) codes with dedicated modules that capture these exotic processes allows for a global description of...
We present a thorough analysis of the properties of the hybrid stars based on a recently developed version the Polyakov Loop coupled Nambu-Jona-Lasinio model of quark phase that maintains the Polyakov loop dynamics in the limit of zero temperature. First, we demonstrate that incorporation of the Polyakov loop to the model significantly stiffens the quark matter equation of state, which is...
Jets have been extensively observed in X-ray Binaries with Black Holes (BHs) or Neutron Stars (NSs), but jet properties in the two classes have several peculiar differences. In the last few years, the flat radio-to-mid-IR spectra of BH X-ray binaries was described using the internal shocks model, which assumes fluctuations in the velocity of the ejected shells along the jet driven by the...
We explore the diffusion of charged in a pulsar magnetosphere by considering the adiabatic invariants describing the motion of particles due to an electric and magnetic field. Charged particles will perform a helical motion round a magnetic field line, they will be bounce between the northern and Southern Hemisphere and drift in the azimuthal direction forming a ring current. While these...
Magnetars are young neutron stars with high surface magnetic fields, exceeding $10^{13}$ Gauss. Pulsed non-thermal quiescent X-ray emission extending between 10 keV to >150 keV has been observed in about 10 magnetars by RXTE, INTEGRAL, Suzaku, NuSTAR and Fermi-GBM. For inner magnetospheric models of such hard X-ray signals, inverse resonant Compton upscattering of soft thermal photons from the...
We compute the polarization of radiation from two hot spots at surface of an oblate neutron star. We account for rotation of the polarization plane due to relativistic effects along the path from the star surface to the observer. We show that the obtained polarization angle (PA) may differ substantially from the corresponding values derived for a spherical star. We also study, with a toy...
I will discuss our recently-published magnetospheric model for repeating FRBs generated during short bursts in magnetars with low-twist magnetospheres. I will detail current observational evidence supporting the model. Some theoretical and heuristic expectations of phenomenology will be discussed. Finally, I will detail how the model may be tested in the future, as well as implications of what...
The electromagnetic observations following the detection of gravitational waves from GW170817 by the LIGO-Virgo collaboration, have confirmed the occurrence of an r-process nucleosynthesis triggered by the decompression of ejected crustal materials from binary neutron star mergers. Magnetars - strongly magnetised isolated neutron stars - might be another astrophysical site for the r-process,...
Neutron star mergers are unique multi-messenger laboratories of accretion, ejection, and r-process nucleosynthesis. Theoretically, however, our current understanding of such events is limited, especially of magnetic effects, such as the role the post-merger magnetic field geometry has on the evolution of merger remnant accretion disks. Through the use of 3D general relativistic...
Pulsar-timing is plagued by several sources of noise whose physical origin is unclear. In recent years, pulsar magnetosphere models have shown that reconnection around the light cylinder plays a key role in particle acceleration and in the origin of the pulsed gamma-ray emission. The pulsar current sheet breaks up into a series of dynamical magnetic islands, which in turn lead to fast and...
