Spherically symmetric, time-periodic oscillatons—solutions of the Einstein-Klein-Gordon system (a massive scalar field coupled to gravity) with a spatially localized core—are investigated by very precise numerical techniques based on spectral methods. In particular, the amplitude of their standing-wave tail is determined. It is found that the amplitude of the oscillating tail is very small, but nonvanishing for the range of frequencies considered. It follows that exactly time-periodic oscillatons are not truly localized, and they can be pictured loosely as consisting of a well (exponentially) localized nonsingular core and an oscillating tail making the total mass infinite. Finite mass physical oscillatons with a well localized core—solutions of the Cauchy-problem with suitable initial conditions—are only approximately time-periodic. They are continuously losing their mass because the scalar field radiates to infinity. Their core and radiative tail is well approximated by that of time-periodic oscillatons. Moreover the mass loss rate of physical oscillatons is estimated from the numerical data and a semiempirical formula is deduced. The numerical results are in agreement with those obtained analytically in the limit of small amplitude time-periodic oscillatons.

• Received 14 July 2011

DOI:https://doi.org/10.1103/PhysRevD.84.065037