Stable Schwarzschild stars as black-hole mimickers
Authors
KONOPLYA, Roman (804 Ukraine, guarantor, belonging to the institution), Nelson Camilo POSADA AGUIRRE (170 Colombia, belonging to the institution), Zdeněk STUCHLÍK (203 Czech Republic, belonging to the institution) and Olexandr ZHYDENKO (804 Ukraine, belonging to the institution)
The Schwarzschild star is an ultracompact object beyond the Buchdahl limit, which has Schwarzschild geometry outside its surface and positive pressure in the external layer which vanishes at the surface. Recently, it has been shown that the Schwarzschild star is stable against spherically symmetric perturbations. Here we study arbitrary axial nonspherical perturbations and show that the observable quasinormal modes can be as close to the Schwarzschild limit as one wishes, what makes the Schwarzschild star a very good mimicker of a black hole. The decaying time-domain profiles prove that the Schwarzschild star is stable against nonspherical perturbations as well. Another peculiar feature is the absence of echoes at the end of the ringdown. Instead we observe a nonoscillating mode which might belong to the class of algebraically special modes. At asymptotically late times, Schwarzschildian power-law tails dominate in the signal.