Institut für Astronomie & Astrophysik

Black hole spectroscopy by ground based detectors

February 2017

Andrea Maselli, Kostas D. Kokkotas, Pablo Laguna

Black holes far from the equilibrium are strong emitters of gravitational radiation. They present rich spectrum of oscillations, called quasi normal modes (QNM), acting as a superposition of exponentially damped sinusoids, which decay until the black hole reaches a stationary quiet state, described by the Kerr metric. QNM carry precious information on the nature of the compact object, and, within General Relativity, they depend uniquely on the black hole mass and spin. Any deviation from such dependence may represent a crucial hint of the existence of exotic objects, or of a more fundamental theory. Gravity tests based on black hole spectroscopy require a detailed knowledge of the oscillations and of their uncertainties.

In our work we assess the detectability of QNM, produced by stellar mass black holes, by current and future ground based interferometers. Assuming different astrophysical scenario, we analyze the errors on the most relevant components of the QNM spectrum. We determine the accuracy with which LIGO and future facilities may constrain the mode parameters, i.e. frequencies and damping times, showing how they affect the black hole mass and spin measurements. We also analyze how a network of terrestrial observatories at design sensitivity improve these results, being a crucial and necessary ingredient to detect multiple QNM, which in turn, are essential to uniquely identify the ultimate nature of the perturbed compact object.