  Black holes (BHs) play a central role in physics. However, gathering
observational evidence for their existence is a notoriously difficult task.
Current strategies to quantify the evidence for BHs all boil down to looking
for signs of highly compact, horizonless bodies. Here, we study particle
creation by objects which collapse to form ultra-compact configurations, with
surface at an areal radius $R=R_{f}$ satisfying $1-(2M/R_{f})= \epsilon^{2}\ll
1$ with $M$ the object mass. We assume that gravitational collapse proceeds in
a `standard' manner until $R=R_{f}+2M \epsilon^{2\beta}$, where $\beta>0$, and
then slows down to form a static object of radius $R_{f}$. In the standard
collapsing phase, Hawking-like thermal radiation is emitted, which is as strong
as the Hawking radiation of a BH with the same mass but lasts only for $\sim
40~(M/M_{\odot})[44+\ln (10^{-19}/\epsilon)]~\mu \mbox{s}$. Thereafter, in a
very large class of models, there exist two bursts of radiation separated by a
very long dormant stage. The first burst occurs at the end of the transient
Hawking radiation, and is followed by a quiescent stage which lasts for $\sim
6\times 10^{6}~(\epsilon/10^{-19})^{-1}(M/M_{\odot})~\mbox{yr}$. Afterwards,
the second burst is triggered, after which there is no more particle production
and the star is forever dark. In a model with $\beta=1$, both the first and
second bursts outpower the transient Hawking radiation by a factor $\sim
10^{38}(\epsilon/10^{-19})^{-2}$.
