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We study the optical appearance and the apparent radiation flux of a thinaccretion disk around the static Janis-Newman-Winicour naked singularity. Weconfine ourselves to the astrophysically most relevant case, when the solutionpossesses a photon sphere, assuming that the radiation emitted by the disk isdescribed by the Novikov-Thorne model. The observable images resemble closelythe visual appearance of the Schwarzschild black hole, as only quantitativedifferences are present. For the Janis-Newman-Winicour solution the accretiondisk appears smaller, and its emission is characterized by a higher peak of theradiation flux. In addition, the most significant part of the radiation isconcentrated in a closer neighbourhood of the flux maximum. The results areobtained independently by two alternative methods, consisting of asemi-analytical scheme using the spherical symmetry of the spacetime, and afully numerical ray-tracing procedure valid for any stationary and axisymmetricspacetime.

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