Effects of general relativity on nonradial stellar pulsations of compact stars

In the present age of space-based photometry, telescopes such as K2 and TESS are providing pulsation frequencies of stellar objects to unprecedented accuracy, requiring equally precise theoretical models correlating these observations to mass- and composition-dependent characteristics of stars. At this precision, relativistic models are required for compact objects such as white dwarfs and neutron stars. We model these stars as polytropes using the Tolman-Oppenheimer-Volkoff equation, and compute relativistic nonradial stellar pulsations around this equilibrium state. Outside the stellar surface, we integrate the Zerilli equation to locate resonant quasinormal modes, where ingoing gravitational radiation vanishes. We compare the frequencies of a subset of these modes to their corresponding pressure-modes in the Newtonian limit, as a function of the strength of relativity inside the star. Our results contribute to our understanding of the impact of general relativity on stellar oscillations, and can be used to determine the conditions under which the Newtonian approximation is justified.