# Image of the Janis-Newman-Winicour naked singularity with a thin accretion disk

## TL;DR

This paper investigates the optical appearance and radiation flux of a thin accretion disk around the Janis-Newman-Winicour naked singularity, revealing similarities and differences with Schwarzschild black holes through analytical and numerical methods.

## Contribution

It provides a detailed analysis of the accretion disk's appearance around the Janis-Newman-Winicour naked singularity using two independent methods, highlighting observable differences from black holes.

## Key findings

- Images are similar to Schwarzschild black holes but smaller in size.
- The radiation flux peaks higher and is more concentrated near the flux maximum.
- Results are consistent across semi-analytical and numerical approaches.

## Abstract

We study the optical appearance and the apparent radiation flux of a thin accretion disk around the static Janis-Newman-Winicour naked singularity. We confine ourselves to the astrophysically most relevant case, when the solution possesses a photon sphere, assuming that the radiation emitted by the disk is described by the Novikov-Thorne model. The observable images resemble closely the visual appearance of the Schwarzschild black hole, as only quantitative differences are present. For the Janis-Newman-Winicour solution the accretion disk appears smaller, and its emission is characterized by a higher peak of the radiation flux. In addition, the most significant part of the radiation is concentrated in a closer neighbourhood of the flux maximum. The results are obtained independently by two alternative methods, consisting of a semi-analytical scheme using the spherical symmetry of the spacetime, and a fully numerical ray-tracing procedure valid for any stationary and axisymmetric spacetime.