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Radial and non-radial oscillations of protoneutron stars with hyperonic composition
Authors: Thakur, P; Issifu, A; Rather, IA; Lim, Y.; Frederico, T.
Ref.: Eur. Phys. J. C 86(7), 863 (2026)
Abstract: This paper studies radial and non-radial oscillations of protoneutron stars (PNSs) evolving from hot, neutrino-rich states to cold, catalyzed configurations, using a density-dependent relativistic mean-field equation of state (EoS) with nucleonic and hyperonic matter. The fundamental (f) and first pressure ( p1 ) modes are computed in both the Cowling approximation and full general relativity (GR). For the f-mode, the Cowling approximation overestimates the frequency by similar to 24% in the hot phase, increasing to similar to 28% at T=0 for M-B=1.5M(circle dot) , and by similar to 19% (hot/intermediate) rising to similar to 22% at T=0 for M-B=2.3M(circle dot) . For the p(1) -mode, deviations are smaller: similar to 6.7% (hot), peaking at similar to 10% during deleptonization, and decreasing to similar to 6.6% at T=0 . Hyperons slightly increase oscillation frequencies. Stage-dependent f-mode scaling shows that expressing M omega in terms of the effective compactness eta(similar to)=root M-3/I significantly reduces thermal scatter, bringing all evolutionary stages onto a tighter curve. Radial oscillations of a 1.4M(circle dot) PNS show strong sensitivity of displacement and pressure perturbations to thermal state, composition, and compactness, with hyperonic EoSs yielding higher frequencies and modified node structures. Differences in nu 0 and Delta nu n between nucleonic and hyperonic models provide potential observational constraints on the dense matter EoS.
