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 Two Micron All Sky Survey, Wide-field Infrared Survey Explorer, Spitzer, Herschel, and APEX photometry and an IRAM limit from 1.2 to 1200 μm, Spitzer spectroscopy from 5 to 40 μm, and high-resolution Hubble imaging at 1.60 and 2.05 μm 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☉, 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☉ (larger than the observed luminosity due to extinction by the disk), an envelope mass of 0.06 M☉, and a disk radius and mass of 450 AU and 0.002 M☉. The stellar mass is highly uncertain but is estimated to fall between 0.4 and 0.5 M☉. To reproduce the flux and wavelength of the near-infrared scattered-light peak in the spectral energy distribution, we require 5.4 × 10−5 M☉ of gas and dust in each cavity. The disk has a large radius and a mass typical of more evolved T Tauri disks 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.