Decoding horizonless spacetime: plasma-induced features in a rotating wormhole shadow

Abstract We investigate the shadow properties in a recently proposed rotating wormhole spacetime in the presence of a cold and non magnetized plasma environment surrounding the wormhole throat. Using the Hamilton Jacobi formalism, we derive the orbit equation under specific plasma density profiles, where we consider plasma as a dispersive medium and disregard its influence on the background geometry. The electron density distribution is chosen to preserve a generalized Carter constant. We explore the shadow cast by this class of rotating wormhole in the presence of both homogeneous and non-homogeneous plasma as seen by an asymptotic observer. The photon regions are visualized, and the influence of geometric parameters, plasma parameters, and the observer’s inclination angle with the rotation axis on the resulting shadow morphology is analyzed. We tried to implement constraints on the plasma and the geometrical parameters of the wormhole such as the spin parameter and the deviation (from Kerr) parameter in the backdrop of recent observational bounds coming from the deviation from circularity of the shadow boundary ( $$\Delta C$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>Δ</mml:mi> <mml:mi>C</mml:mi> </mml:mrow> </mml:math> ) and deviation of the average shadow radius from Schwarzschild ( $$\delta $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>δ</mml:mi> </mml:math> ). The bound on $$\Delta C$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>Δ</mml:mi> <mml:mi>C</mml:mi> </mml:mrow> </mml:math> is satisfied by the theoretically allowed range of parameters thus not found very useful to put any constraint; we could impose stringent constraints on the parameters based on the observed value of $$\delta $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>δ</mml:mi> </mml:math> . Comparing the optical characteristics of the image of these wormholes with those of Kerr black holes, we identify the features that could serve as discriminants for similar types of compact objects.