Imaging ultra-compact objects with radiatively inefficient accretion flows

Abstract

Recent Event Horizon Telescope observations of M87* and Sgr A* strongly suggests the presence of supermassive black hole at their respective cores. In this work, we use the semi-analytic Radiatively Inefficient Accretion Flows (RIAF) model to investigate the resulting images of Joshi-Malafarina-Narayan (JMN-1) naked singularity and the Schwarzschild BH. We aim at choosing the JMN-1 naked singularity model and compare the synchrotron images with the Schwarzschild solution to search any distinct features which can distinguish the two objects and find alternative to the black hole solution. We perform general relativistic ray-tracing and radiative transfer simulations using Brahma code to generate synchrotron emission images utilising thermal distribution function for emissivity and absorptivity. We investigate effects in the images by varying inclination angle, disk width and frequency. The shadow images simulated by the JMN-1 model closely resemble those generated by the Schwarzschild black hole. When we compare these images, we find that the disparities between them are minimal. We conduct simulations using various plasma parameters, but the resulting images remain largely consistent for both scenarios. This similarity is evident in the horizontal cross-sectional brightness profiles of the two instances. Notably, the JMN-1 model exhibits slightly higher intensity in comparison to the Schwarzschild black hole. We conclude that JMN-1 presents itself as a viable substitute for the black hole scenario. This conclusion is not solely grounded in the fact that they are indistinguishable from their respective shadow observations, but also in the consideration that JMN-1 emerges as an end state of a continual gravitational collapse. This paradigm not only allows for constraints on spacetime but also provides a good probe for the nature of the central compact object.

Accepted in A&A, 7 pages, 6 figures. arXiv admin note: text overlap with arXiv:2202.00588

References in corpus (13)

• First Sagittarius A* Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole in the Center of the Milky Way
• First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring
• Black Hole Shadows, Photon Rings, and Lensing Rings
• First Sagittarius A* Event Horizon Telescope Results. V. Testing Astrophysical Models of the Galactic Center Black Hole
• A new method for shadow calculations: application to parameterised axisymmetric black holes
• Gravastar Shadows
• Shadow of a Naked Singularity without Photon Sphere
• Can strong gravitational lensing distinguish naked singularities from black holes?
• An upper limit on the spin of SgrA${}^{\ast }$ based on stellar orbits in its vicinity
• Shadows and negative precession in non-Kerr spacetime
• Strong curvature naked singularities in spherically symmetric perfect fluid collapse
• Probing spacetime and accretion model for the Galactic Center: Comparison of Kerr and dilaton black hole shadows
• Toward General-Relativistic Magnetohydrodynamics Simulations in Stationary Non-Vacuum Spacetimes

Cited by in corpus (4)

• Relativistic time delay analysis of pulsar signals near ultra-compact objects
• Spin precession frequencies of a test gyroscope around a naked singularity and quasi-periodic oscillations
• Retrograde Precession of Relativistic Orbits and the Quest for Charged Black Holes
• Shadow Formation Conditions Beyond the Kerr Black Hole Paradigm