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Vaidya–Tikekar²⁰ model has been generalised to describe cold compact stars having concentric layers of different phases. We illustrate the model by considering a star whose inner core has a deconfined quark phase, enveloped by less compact baryonic constituents.

We present here a simple model of radiative gravitational collapse with radial heat flux which describes qualitatively the stages close to the formation of a superdense cold star. Starting with a static general solution for a cold star, the model can generate solutions for the earlier evolutionary stages. The temporal evolution of the model is specified by solving the junction conditions appropriate for radiating gravitational collapse. The results will be useful in constructing models for the evolution of X-ray pulsars, like Her X-1.