Multiwavelength Observations of V2775 Ori, an Outbursting Protostar in L
  1641: Exploring the Edge of the FU Orionis Regime
  Individual outbursting young stars are important laboratories for studying
the physics of episodic accretion and the extent to which this phenomenon can
explain the luminosity distribution of protostars. We present new and archival
data for V2775 Ori (HOPS 223), a protostar in the L 1641 region of the Orion
molecular clouds that was discovered by Caratti o Garatti et al. (2011) to have
recently undergone an order-of-magnitude increase in luminosity. Our
near-infrared spectra of the source have strong blueshifted He I 10830
absorption, strong H2O and CO absorption, and no H I emission, all typical of
FU Orionis sources. With data from IRTF, 2MASS, HST, Spitzer, WISE, Herschel,
and APEX that span from 1 to 70 microns pre-outburst and from 1 to 870 microns
post-outburst, we estimate that the outburst began between 2005 April and 2007
March. We also model the pre- and post-outburst spectral energy distributions
of the source, finding it to be in the late stages of accreting its envelope
with a disk-to-star accretion rate that increased from about 2x10^-6 M_sun/yr
to about 10^-5 M_sun/yr during the outburst. The post-outburst luminosity at
the epoch of the FU Orionis-like near-IR spectra is 28 L_sun, making V2775 Ori
the least luminous documented FU Orionis outburster with a protostellar
envelope. The existence of low-luminosity outbursts supports the notion that a
range of episiodic accretion phenomena can partially explain the observed
spread in protostellar luminosities.
