No-Hair Theorem in the Wake of Event Horizon Telescope

Understand

Thanks to the release of the extraordinary EHT image of shadow attributed to the M87* supermassive black hole (SMBH), we have a novel window to assess the validity of fundamental physics in the strong-field regime.

• Motivated by this, we consider Johannsen \& Psaltis metric parameterized by mass, spin, and an additional dimensionless hair parameter $\epsilon$.
• This parametric framework in the high rotation regimes provides a well-behaved bed to the strong-gravity test of the no-hair theorem (NHT) using the EHT data.
• Incorporating the $\epsilon$ into the standard Kerr spacetime enrich it in the sense that, depending on setting the positive and negative values for that, we deal with alternative compact objects: deformed Kerr naked singularity and Kerr BH solutions, respectively.