Are nonsingular black holes with super-Planckian hair ruled out by S2 star data?

Abstract

We propose a novel nonsingular black-hole spacetime representing a strong deformation of the Schwarzschild solution with mass $M$ by an additional hair $\ell$, which may be hierarchically larger than the Planck scale. Our black-hole model presents a de Sitter core and $\mathcal{O}(\ell^2/r^2)$ slow-decaying corrections to the Schwarzschild solution. Our black-hole solutions are thermodynamically preferred when $0.2 \lesssim \ell/GM \lesssim \, 0.3$ and are characterized by strong deviations in the orbits of test particles from the Schwarzschild case. In particular, we find corrections to the perihelion precession angle scaling linearly with $\ell$. We test our model using the available data for the orbits of the S2 star around $\text{SgrA}^*$. These data strongly constrain the value of the hair $\ell$, casting an upper bound on it of $\sim \, 0.47 \, GM$, but do not rule out the possible existence of regular black holes with super-Planckian hair.