In a broad class of theories, the accumulation of ultralight dark matter
(ULDM) with particles of mass 10−22 eV<mϕ​<1 eV
leads the to formation of long-lived bound states known as boson stars. When
the ULDM exhibits self-interactions, prodigious bursts of energy carried by
relativistic bosons are released from collapsing boson stars in bosenova
explosions. We extensively explore the potential reach of terrestrial and
space-based experiments for detecting transient signatures of emitted
relativistic bursts of scalar particles, including ULDM coupled to photons,
electrons, and gluons, capturing a wide range of motivated theories. For the
scenario of relaxion ULDM, we demonstrate that upcoming experiments and
technology such as nuclear clocks as well as space-based interferometers will
be able to sensitively probe orders of magnitude in the ULDM coupling-mass
parameter space, challenging to study otherwise, by detecting signatures of
transient bosenova events. Our analysis can be readily extended to different
scenarios of relativistic scalar particle emission.Comment: 16 pages, 9 figure