Observational identification of a sample of likely recent
  Common-Envelope Events
  One of the most poorly understood stellar evolutionary paths is that of
binary systems undergoing common-envelope evolution, when the envelope of a
giant star engulfs the orbit of a companion. Although this interaction leads to
a great variety of astrophysical systems, direct empirical studies are
difficult because few objects experiencing common-envelope evolution are known.
We present ALMA observations towards sources known as water fountains that
reveal they had low initial masses ($<4~{\rm M}_\odot$) and ejected a
significant fraction of it over less than a few hundred years. The only
mechanism able to explain such rapid mass ejection is common-envelope
evolution. Our calculations show that the water-fountain sample accounts for a
large fraction of the systems in our Galaxy which have just experienced the
common-envelope phase. Since water-fountain sources show characteristic fast
bipolar outflows, outflows and jets likely play an important role right before,
during or immediately after the common-envelope phase.
