Related papers: Testing Strong-field Gravity with Quasi-Periodic O…
As the densities in the interior of neutron stars exceed those of terrestrial nuclear experiments, they provide a scope for studying the nature of dense matter under extreme conditions. The composition of the inner core of neutron stars is…
A stability analysis of a spherically symmetric star in scalar-tensor theories of gravity is given in terms of the frequencies of quasi-normal modes. The scalar-tensor theories have a scalar field which is related to gravitation. There is…
In the present paper we investigate self-consistently slowly rotating neutron and strange stars in R-squared gravity. For this purpose we first derive the equations describing the structure of the slowly rotating compact stars in…
We study polar quasinormal modes of relativistic stars in scalar-tensor theories, where we include a massive gravitational scalar field and employ the standard Brans-Dicke coupling function. For the potential of the scalar field we consider…
Scalar-tensor~(ST) theories of gravity are natural phenomenological extensions to general relativity. Although these theories are severely constrained both by solar system experiments and by binary pulsar observations, a large set of ST…
Recent X-ray variability observations of accreting neutron stars may provide the first evidence for frame dragging effects around spinning relativistic objects. Motivated by this possibility and its implications for neutron-star structural…
We study the frequency shift of photons generated by rotating gravitational sources in the framework of curvature based Extended Theories of Gravity. The discussion is developed considering the weak-field approximation. Following a…
Gravitational wave observations can potentially measure properties of neutron star equations of state by measuring departures from the point-particle limit of the gravitational waveform produced in the late inspiral of a neutron star…
The dramatic discovery with the Rossi X-Ray Timing Explorer satellite of remarkably coherent $\sim$300--1200 Hz oscillations in the X-ray brightness of some sixteen neutron stars in low-mass binary systems has spurred theoretical modeling…
The characteristic physical timescales near stellar-mass compact objects are measured in milliseconds. These timescales -- the free-fall time, the fastest stable orbital period, and stellar spin periods -- encode the fundamental physical…
Strongly magnetized, accreting neutron stars show periodic and aperiodic variability over a wide range of time scales. By obtaining spectral and timing information on these different time scales, we can have a closer look into the physics…
We develop a general formalism to treat, in general relativity, the linear oscillations of a two-fluid star about static (non-rotating) configurations. Such a formalism is intended for neutron stars, whose matter content can be described,…
Black holes in our Universe are rarely truly isolated, being instead embedded in astrophysical environments such as plasma or dark matter. A particularly intriguing possibility is that light scalar fields form bound states around black…
We study slowly-rotating neutron stars in ghost-free massive bigravity. This theory modifies General Relativity by introducing a second, auxiliary but dynamical tensor field that couples to matter through the physical metric tensor through…
The excitation of the axial quasi-normal modes of a relativistic star by scattered particles is studied by evolving the time dependent perturbation equations. This work is the first step towards the understanding of more complicated…
Soft gamma repeaters and anomalous X-ray pulsars are thought to be magnetars, neutron stars with strong magnetic fields of order $\mathord{\sim} 10^{13}$--$10^{15} \, \mathrm{gauss}$. These objects emit intermittent bursts of hard X-rays…
We study neutrino spin oscillations in gravitational fields. The quasi-classical approach is used to describe the neutrino spin evolution. First we examine the case of a weak gravitational field. We obtain the effective Hamiltonian for the…
Gravitational lensing serves as a powerful probe of compact astrophysical objects and dark matter distributions. As relativistic counterparts to photons, neutrinos experiencing lensing offer a complementary means to investigate the…
We consider the nonunitary quantum dynamics of neutral massless scalar particles used to model photons around a massive gravitational lens. The gravitational interaction between the lensing mass and asymptotically free particles is…
$f(R)$ theories of gravity are one of the most popular alternative explanations for dark energy and therefore studying the possible astrophysical implications of these theories is an important task. In the present paper we make a…