HOPS 136: An Edge-On Orion Protostar Near the End of Envelope Infall
  Edge-on protostars are valuable for understanding the disk and envelope
properties of embedded young stellar objects, since the disk, envelope, and
envelope cavities are all distinctly visible in resolved images and well
constrained in modeling. Comparing 2MASS, WISE, Spitzer, Herschel, APEX, and
IRAM photometry and limits from 1.25 to 1200 microns, Spitzer spectroscopy from
5 to 40 microns, and high-resolution Hubble imaging at 1.60 and 2.05 microns to
radiative transfer modeling, we determine envelope and disk properties for the
Class I protostar HOPS 136, an edge-on source in Orion's Lynds 1641 region. The
source has a bolometric luminosity of 0.8 L_sun, a bolometric temperature of
170 K, and a ratio of submillimeter to bolometric luminosity of 0.8%. Via
modeling, we find a total luminosity of 4.7 L_sun (larger than the observed
luminosity due to extinction by the disk), an envelope mass of 0.06 M_sun, and
a disk radius and mass of 450 AU and 0.002 M_sun. The stellar mass is highly
uncertain but is estimated to fall between 0.4 and 0.5 M_sun. To reproduce the
flux and wavelength of the near-infrared scattered-light peak in the spectral
energy distribution, we require 5.4 x 10^-5 M_sun of gas and dust in each
cavity. The disk has a large radius and a mass typical of more evolved T Tauri
stars in spite of the significant remaining envelope. HOPS 136 appears to be a
key link between the protostellar and optically revealed stages of star
formation.
