Gaia 17bpi: An FU Ori Type Outburst
  We report on the source Gaia 17bpi and identify it as a new, ongoing FU Ori
type outburst, associated with a young stellar object. The optical lightcurve
from Gaia exhibited a 3.5 mag rise with the source appearing to plateau in
mid/late 2018. Mid-infrared observations from NEOWISE also show a $>$3 mag rise
that occurred in two stages, with the second one coincident with the optical
brightening, and the first one preceding the optical brightening by $\sim$1.5
years. We model the outburst as having started between October and December of
2014. This wavelength-dependent aspect of young star accretion-driven outbursts
has never been documented before. Both the mid-infrared and the optical colors
of the object become bluer as the outburst proceeds. Optical spectroscopic
characteristics in the outburst phase include: a GK-type absorption spectrum,
strong wind/outflow in e.g. Mgb, NaD, H$\alpha$, KI, OI, and CaII profiles, and
detection of LiI 6707 \AA. The infrared spectrum in the outburst phase is
similar to that of an M-type spectrum, notably exhibiting prominent $H_2O$ and
$^{12}$CO (2-0) bandhead absorption in the K-band, and likely HeI wind in the
Y-band. The new FU Ori source Gaia 17bpi is associated with a little-studied
dark cloud in the galactic plane, located at a distance of 1.27 kpc.
