Infrared spectroscopy of eruptive variable protostars from VVV
  In a companion work (Paper I) we detected a large population of highly
variable Young Stellar Objects (YSOs) in the Vista Variables in the Via Lactea
(VVV) survey, typically with class I or flat spectrum spectral energy
distributions and diverse light curve types. Here we present infrared spectra
(0.9--2.5 $\mu$m) of 37 of these variables, many of them observed in a bright
state. The spectra confirm that 15/18 sources with eruptive light curves have
signatures of a high accretion rate, either showing EXor-like emission features
($\Delta$v=2 CO, Br$\gamma$) and/or FUor-like features ($\Delta$v=2 CO and
H$_{2}$O strongly in absorption). Similar features were seen in some long term
periodic YSOs and faders but not in dippers or short-term variables. The sample
includes some dusty Mira variables (typically distinguished by smooth Mira-like
light curves), 2 cataclysmic variables and a carbon star. In total we have
added 19 new objects to the broad class of eruptive variable YSOs with episodic
accretion. Eruptive variable YSOs in our sample that were observed at bright
states show higher accretion luminosities than the rest of the sample. Most of
the eruptive variables differ from the established FUor and EXor subclasses,
showing intermediate outburst durations and a mixture of their spectroscopic
characteristics. This is in line with a small number of other recent
discoveries. Since these previously atypical objects are now the majority
amongst embedded members of the class, we propose a new classification for them
as MNors. This term (pronounced emnor) follows V1647 Ori, the illuminating star
of McNeil's Nebula.
