Periodic gravitational lensing by oscillating boson stars

TL;DR

Oscillating boson stars can serve as periodic gravitational lenses, creating observable photometric and astrometric signals that can be detected with current surveys, providing a new way to test self-gravitating quantum fields.

Contribution

This work demonstrates that oscillating boson stars can produce periodic gravitational lensing effects, including radial caustics and synchronized photometric and astrometric signals, which had not been previously identified.

Findings

Detection of achromatic phase-locked photometric spikes.

Prediction of observable signals with current surveys.

Extension of framework to axion-like particles and ultralight vectors.

Abstract

We show that oscillating (real-scalar) boson stars can act as strictly periodic gravitational lenses and generically host an \emph{oscillating radial caustic}. Sources near this caustic cross it every half period, producing achromatic phase-locked photometric spikes synchronized with an astrometric wobble, providing a promising target for time-domain astronomy. Event-number estimation indicates a measurable discovery space with current astrometric and high-cadence photometric surveys. These predictions rely only on the dynamics of long-lived real-scalar condensates, therefore offering a clean test of self-gravitating quantum fields in curved spacetime. The framework extends naturally to self-interacting real scalars (including axion-like particles) and to ultralight vector bosons.