The phase structure of hadronic matter at high density could be extremely rich. In particular, several effective model calculations, as well as more refined studies based directly on QCD, suggest that spatially inhomogeneous phases might form in cold and dense quark matter, possibly leading to significant phenomenological consequences for the physics of compact stars.
In this contribution,...
Nuclear systems exist in nature in a wide range of sizes and densities. Nuclear equation of state (EoS) is thus immensely important to know the basic nature of nucleon-nucleon interaction. As the exact nature of this interaction is still not known, there exist a huge number of EoSs in the literature based on different relativistic and non-relativistic interactions. Based on recent observations...
Pasta phases are believe to exist in the inner core of neutron stars and in the low density regions of core-collapse supernovae. The search for the existence of nuclear pasta phases in this region is performed within the context of two versions of the quark-meson coupling (QMC) model. Fixed proton fractions are considered, as well as nuclear matter in β equilibrium at zero temperature. We...
We revisit the Polyakov Loop coupled Nambu-Jona-Lasinio model that maintains the Polyakov loop dynamics in the limit of zero temperature. For this purpose we re-examine the form of the potential for the deconfinement order parameter at finite baryonic densities. Secondly, and the most important, we explicitly demonstrate that a modification of this potential at any temperature is formally...
The appearance of quark matter may show a different property with traditional NS in the cooling process. With this purpose, we investigate the cooling of hybrid star. For the hadronic sector, we use a microscopic EOS derived within the Brueckner-Hartree-Fock many-body theory with realistic two-body and three-body forces. For the description of quark matter, we employ the Dyson-Schwinger quark...
We study an impact of asymmetric dark matter on properties of the neutron stars and their ability to reach the two solar masses limit, which allows us to present a new upper constraint on the mass of dark matter particle. Our analysis is based on the observational fact of existence of three pulsars reaching this limit and on the theoretically predicted reduction of the neutron star maximal...
The subpulse drifting, seen as periodic modulations in the single pulse radio emission, provides a direct observational window into the inner acceleration region (IAR) of pulsars. The drifting is associated with the sparking discharges responsible for the non-stationary plasma flow, where the sparks are expected to undergo ExB drift in the IAR. However, there is significant diversity observed...
We have shown that the torques acting on the intermittent pulsars in the radio ON and OFF states can be reproduced by transitions between the strong and weak propeller phases of accreting neutron stars evolving with fallback discs. We have used the analytical model applied earlier to the transitional millisecond pulsars to explain their properties during transitions between the radio pulsar...
Single pulses from pulsar are highly variable in shape, width etc, but the average profile is stable. Average profile of a pulsar is a unique property of any given pulsar, making it a best way to characterize the emission geometry. The evolution of pulse profile morphology with period and frequency is a study till date, and the pulse profiles are often classified based on number of visible...
We discuss a detailed study of single-pulse detections from RRAT J1819-1458, with observations taken across a long period of time. Additionally to the usual sporadic nature of RRATs, this source exhibits a strong variation in the flux, shape and the number of components of the individual pulse detections. The arrival times of separate components have been examined in the past, which resulted...
We present the results of multi frequency single pulse observations of PSR B0329+54 and PSR B1133+16. The observations were conducted over a very wide range of frequencies, from 100 MHz to 8 GHz, using instruments such as LOFAR single stations, GMRT and Effelsberg. Large parts of these observations were conducted simultaneously at three or more frequencies. Our main golas were to study the...
There is strong observational evidence that coherent radio emission from pulsars are excited by curvature radiation from charge bunches in relativistically streaming plasma along the open dipolar magnetic field lines, and detaches the pulsar magnetosphere below 10% of the light cylinder radius. The formation of charge bunches requires growth of instabilities in the plasma, however the exact...
We revisit the accretion induced collapse (AIC) process, in which a white dwarf collapses into a neutron star. We are motivated by the persistent radio source associated with the fast radio burst 121102, which was explained by Waxman (2017) as a weak stellar explosion with a small (∼ $10^{-5}\,M_\odot$) mass ejection. Since a typical supernova ejects much larger amount of mass, we study the...
Detection of twin peak quasi-periodic oscillations in power-density spectra of low-mass X-ray binaries can be used to constrain mass of the compact object. In this presentations we will apply the so-called cusp torus model to neutron star in 4U 1646-53 to determine the mass of the neutron star. We will also discuss the possibility to constrain the radius of the neutron star as well.
This paper studies the formation of Millisecond Pulsars (MSPs) and the dynamical
characterisation of their parameters with a distribution of long (Porb > 2d) circular (e ≤ 0.1) orbits. For this task, a distinct approach to the analysis of the orbital parameters of binary MSPs (in Galactic disk and globular cluster) produced by the asymmetric kick imparted during the Accretion Induced Collapse...
We present a recent Chandra observation of the quiescent low-mass X-ray binary containing a neutron star, located in the globular cluster M30. We fit the thermal emission from the neutron star to extract its mass and radius. We find no evidence of flux variability between the two observations taken in 2001 and 2017, so we analyze them together to increase the signal to noise. We perform...
Pulsars with millisecond spin periods and weak magnetic fields (~10^8 G) are thought to be spun up through a 0.1–1 Gyr-long phase by the transfer of matter and angular momentum from a low mass companion star. When the mass transfer is active, these neutron stars can be observed as accretion-powered millisecond X-ray pulsar, provided that their magnetic field is strong enough to channel the...
- Context: Recent studies have suggested that a variety of heavy elements, whose origin is still debated, is synthesized as a result of nuclear reactions during X-ray bursts. The predicted luminosities indicate these heavy elements may escape neutron stars gravity through a radiative stellar wind, thus contributing to the observed galactic abundances. Stellar wind models, though studied in...
Thermonuclear bursts from neutron stars in low-mass X-ray binaries are the subject of advanced research on accretion and nuclear burning processes. Depending on the accretion rate and composition of the stellar material, bursts lasting tens of minutes can be explained by the ignition of an unusually thick pure helium layer, though the role of hydrogen remains uncertain in some systems....
Young neutron stars provide unique insights into astrophysics that are not available from the bulk of the pulsar population. The smooth spin-down of young radio pulsars is perturbed by two non-deterministic phenomenon, timing noise and glitches. Timing noise is a type of rotational irregularity which causes the pulse arrival times to stochastically wander about a steady spin-down state while...
This talk explores whether gravitational waves (GWs) from neutron star (NS) mountains can be detected with current 2nd-generation and future 3rd-generation GW detectors. In particular, we focus on a scenario where transient mountains are formed immediately after a glitch. In a glitch, the NS's spin frequency abruptly increases and then often exponentially relaxes back to, but never quite...