Escape and Trapping of Low-Frequency Gravitationally Lensed Rays by Compact Objects within Plasma

Abstract

We consider the gravitational lensing of rays emitted by a compact object (CO) within a distribution of plasma with power-law density $\propto r^{-h}$. For the simplest case of a cloud of spherically symmetric cold non-magnetized plasma, the diverging effect of the plasma and the converging effect of gravitational lensing compete with one another. When $h<2$, the plasma effect dominates over the vacuum Schwarzschild curvature, potentially shifting the radius of the unstable circular photon orbit outside the surface of the CO. When this occurs, we define two relatively narrow radio-frequency bands in which plasma effects are particularly significant. Rays in the escape window have ${\omega }_0<\omega \le {\omega }_{+}$ and are free to propagate to infinity from the CO surface. To a distant observer, the visible portion of the CO surface appears to shrink as the observed frequency is reduced, and vanishes entirely at ${\omega }_0$, in excess of the plasma frequency at the CO surface. We define the anomalous propagation window for frequencies ${\omega }_{-}<\omega \le {\omega }_0$. Rays emitted from the CO surface within this frequency range are dominated by optical effects from the plasma and curve back to the surface of the CO, effectively cloaking the star from distant observers. We conclude with a study of neutron star (NS) compactness ratios for a variety of nuclear matter equations of state (EoS). For $h=1$, NSs generated from stiff EoS should display significant frequency dependence in the EW, and lower values of $h$ with softer EoS can also show these effects.

arXiv comment10 pages, 4 figures. Updated to match published version

References in corpus (36)

• LOFAR: The LOw-Frequency ARray
• Schwarzschild black hole lensing
• The Axisymmetric Pulsar Magnetosphere
• Relativistic images of Schwarzschild black hole lensing
• Influence of a plasma on the shadow of a spherically symmetric black hole
• Shadow of rotating regular black holes
• Small, Dense Quark Stars from Perturbative QCD
• Optical properties of black hole in the presence of plasma: shadow
• Observing pulsars and fast transients with LOFAR
• Frequency-dependent effects of gravitational lensing within plasma
• Magnetar Spin-Down
• A LOFAR census of non-recycled pulsars: average profiles, dispersion measures, flux densities, and spectra
• Light Curves for Rapidly-Rotating Neutron Stars
• A LOFAR census of millisecond pulsars
• Wide-band Simultaneous Observations of Pulsars: Disentangling Dispersion Measure and Profile Variations
• Effects of plasma on gravitational lensing
• Gravitational lensing in plasma: Relativistic images at homogeneous plasma
• Gravitational lensing in a non-uniform plasma
• Wide-Band, Low-Frequency Pulse Profiles of 100 Radio Pulsars with LOFAR
• Covariant Magnetoionic Theory I: Ray Propagation
• Gravitational radiospectrometer
• Pulsar Observations Using the First Station of the Long Wavelength Array and the LWA Pulsar Data Archive
• Covariant Magnetoionic Theory II: Radiative Transfer
• Wind braking of magnetars
• Shadow of a Charged Rotating Black Hole in $f(R)$ Gravity
• Space-based Aperture Array For Ultra-Long Wavelength Radio Astronomy
• Low-Frequency Spectral Turn-Overs in Millisecond Pulsars Studied from Imaging Observations
• Detection and Flux Density Measurements of the Millisecond Pulsar J2145-0750 below 100 MHz
• FIRST Explorer -- An innovative low-cost passive formation-flying system
• Magnetars as Highly Magnetized Quark Stars: an analytical treatment
• A Cosmic Census of Radio Pulsars with the SKA
• Circular polarization shows the nature of pulsar magnetosphere composition
• PSR B1133+16: radio emission height and plasma composition
• Ion-proton pulsars
• Low Frequency Observations of Millisecond Pulsars with the WSRT
• Shadow of the rotating black hole with quintessential energy in the presence of the plasma

Cited by in corpus (37)

• Calculating black hole shadows: Review of analytical studies
• Weak lensing in a plasma medium and gravitational deflection of massive particles using the Gauss-Bonnet theorem. A unified treatment
• Light propagation in a plasma on Kerr spacetime: Separation of the Hamilton-Jacobi equation and calculation of the shadow
• Gravitational Lensing in presence of Plasma: Strong Lens Systems, Black Hole Lensing and Shadow
• Shadow analysis for rotating black holes in the presence of plasma for an expanding universe
• Shadow and deflection angle of charged rotating black hole surrounded by perfect fluid dark matter
• Higher order corrections to deflection angle of massive particles and light rays in plasma media for stationary spacetimes using the Gauss-Bonnet theorem
• Two families of astrophysical diverging lens models
• Finite distance corrections to the light deflection in a gravitational field with a plasma medium
• Gravitational lensing in dispersive media and deflection angle of charged massive particles in terms of curvature scalars and energy-momentum tensor
• Gravitational lensing for a boosted Kerr black hole in the presence of plasma
• Motion of Particles and Gravitational Lensing Around (2+1)-dimensional BTZ black holes in Gauss-Bonnet Gravity
• Deflection of light rays by spherically symmetric black hole in dispersive medium
• Gravitational Lensing of Rays through the Levitating Atmospheres of Compact Objects
• On parametrised cold dense matter equation of state inference
• Hills and holes in the microlensing light curve due to plasma environment around gravitational lens
• Strong deflection limit analysis of black hole lensing in inhomogeneous plasma
• Shadow of black hole surrounded by magnetized plasma: Axion-plasmon cloud
• Weak gravitational lensing: a compact object with arbitrary quadrupole moment immersed in plasma
• Weak Deflection angle and Shadow by Tidal Charged Black Hole
• Gravitational lensing around Kehagias-Sfetsos compact objects surrounded by plasma
• Two families of elliptical plasma lenses
• Sachs equations for light bundles in a cold plasma
• Light deflection by squashed Kaluza-Klein black holes in a plasma medium
• Time delay induced by plasma in strong lens systems
• Analytical expressions for pulse profile of neutron stars in plasma environments
• Binary microlensing with plasma environment -- Star and planet
• Dual-Component Plasma Lens Models
• On the double-plane plasma lensing
• Perturbative and numerical approach to plasma strong lensing
• Effects of the refractive index of the X-ray corona on the emission lines in AGN
• Deflection of light rays in a moving medium around a spherically symmetric gravitating object
• Observational signatures of Rotating compact objects in Plasma space-time
• Boosted Kerr black hole in the presence of plasma
• Deciphering signatures of Kerr-Sen black holes in presence of plasma from the Event Horizon Telescope data
• Flux of radiation from pointlike sources in general relativity
• Light deflection in axially symmetric stationary spacetimes filled with a moving medium