Outbursts on young stars are usually interpreted as accretion bursts
caused by instabilities in the disk or the star-disk connection.
However, some protostellar outbursts may not fit into this framework. In
this paper, we analyze optical and near-infrared spectra and photometry
to characterize the 2015 outburst of the probable young star
ASASSN-15qi. The ˜3.5 mag brightening in the V band was sudden, with
an unresolved rise time of less than one day. The outburst decayed
exponentially by 1 mag for 6 days and then gradually back to the
pre-outburst level after 200 days. The outburst is dominated by emission
from ˜10,000 K gas. An explosive release of energy accelerated
matter from the star in all directions, seen in a spectacular cool,
spherical wind with a maximum velocity of 1000 km s^-1.
The wind and hot gas both disappeared as the outburst faded and the
source returned to its quiescent F-star spectrum. Nebulosity near the
star brightened with a delay of 10-20 days. Fluorescent excitation
of H₂ is detected in emission from vibrational levels as high
as v = 11, also with a possible time delay in flux increase. The
mid-infrared spectral energy distribution does not indicate the presence
of warm dust emission, though the optical photospheric absorption and CO
overtone emission could be related to a gaseous disk. Archival
photometry reveals a prior outburst in 1976. Although we speculate about
possible causes for this outburst, none of the explanations are
compelling.