Study of quasinormal modes, greybody bounds, and sparsity of Hawking radiation within the metric-affine bumblebee gravity framework

Abstract

We consider a static and spherically symmetric black hole metric that emerges from the vacuum solution of the traceless metric-affine bumblebee model. Our study focuses on the possible implications of the modifications induced by the model on various astrophysical observables that include quasinormal modes, ringdown waveforms, Hawking radiation spectrum, sparsity of that radiation, and the lifetime of a black hole. We explore the impact of the Lorentz symmetry-breaking parameter $\alpha$ on the quasinormal modes with the help of the $6th$-order WKB method. Our inquisition reveals that the emission frequency and decay rate initially decrease with $\alpha$ and then grow up. As a result, the LSB becomes critically important for maintaining the stability of the system after being exposed to perturbation. The convergence of the WKB method for various orders is also studied here. We then analyze the Hawking temperature, radiation spectrum, and sparsity in this modified gravity framework that provides valuable insights into the thermal radiation emitted by black holes. It points out that the Hawking temperature, the peak of the power spectrum, and the total power emitted initially decreases and then increases with $\alpha$. However, The variation of the sparsity with $\alpha$ follows a reverse trend. Finally, we obtain the analytical expression of the 'lifetime' of black holes and scrutinize the effect of $\alpha$ on it.