Introducing the Search for Intermediate-mass Black-hole In Nearby Galaxy
  (SIBLING) Survey
  Intermediate mass black holes (IMBHs) have masses between the $10^2\!-\!10^6$
M$_\odot$ and are key to our understanding of the formation of massive black
holes. The known population of IMBH remains small, with a few hundred
candidates and only a handful of them confirmed as bona-fide IMBHs. Until now,
the most widely used selection method is based on spectral analysis. Here we
present a methodology to select IMBH candidates via optical variability
analysis of the nuclear region of local galaxies ($z \leqslant 0.35$). Active
IMBH accreting at low rates show small amplitude variability with time scales
of hours, as it is seen in one of the known IMBH NGC4395. We found a sample of
$\sim \!500$ galaxies evidencing fast and small amplitude variation in their
weekly based light curves. We estimate an average occupancy fraction of 4\% and
a surface density of $\sim \!3$ deg$^{-2}$, which represent an increase by a
factor of $\sim\!40$ compared to previous searches. A large fraction ($78\%$)
of the candidates are in spiral galaxies. We preliminary confirm the AGN nature
of 22 sources via BPT diagrams using SDSS legacy spectra. Further confirmation
of these candidates will require multiwavelength observations, especially in
X-ray and radio bands.
