Stable relativistic polytropic objects with cosmological constant

Equilibrium, radial stability and non-adiabatic gravitational collapse of anisotropic neutron stars

“…7, the degree of anisotropy in the pressures increases as the star collapses and it always vanishes at the origin as well as at the surface for any instant of time. The radial profile of the mass function (46) is displayed in the intermediate panel of the same figure, indicating that it decreases during the gravitational collapse due to the emission of particles into outer spacetime. On the stellar surface and at the moment of event horizon formation, we have m(t bh , R) = 1.335 M which precisely coincides with the value obtained by means of the junction condition (61).…”

“…In general relativity (GR), the stability analysis for isotropic compact stars with respect to radial perturbations has been widely discussed in the literature [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46], whereas within the context of anisotropic configurations the normal radial modes technique has been used only in some specific cases, see e.g., [17,20,[47][48][49][50]. In particular, for anisotropic strange stars described by the MIT bag model EoS, it was shown that the M (ρ c ) method is not compatible with the calculation of frequencies to predict the onset of instability [20] for the anisotropy profile proposed by Bowers and Liang [14], this is, the maximummass stellar configurations do not correspond to the zero squared frequencies of the fundamental mode.…”

“…Radial profile of the anisotropy ansatz (upper panel) described by Eq. (66), mass function (intermediate panel)given by(46), and expansion scalar (lower panel) during the collapse process at different instants of time. The results are for the same solution as in Fig.5.…”

Effect of cosmological constant on radial oscillations and gravitational wave echoes of strange stars

“…They have also studied the impact of cosmological constant on the critical adiabatic index. Recently, for stable relativistic polytropic objects the effect of cosmological constant is reported in [22]. A more detailed analysis on the stability of polytropic sphere in the presence of a cosmological constant can be found in [23].…”