IGRINS spectroscopy of Class I sources: IRAS 03445+3242 and IRAS
  04239+2436
  We have detected molecular and atomic line emission from the hot and warm
disks of two Class I sources, IRAS 03445+3242 and IRAS 04239+2436 using the
high resolution Immersion GRating INfrared Spectrograph (IGRINS). CO overtone
band transitions and near-IR lines of Na I and Ca I, all in emission, trace the
hot inner disk while CO rovibrational absorption spectra of the first overtone
transition trace the warm gas within the inner few AU of the disk. The
emission-line profiles for both sources show evidence for Keplerian disks. A
thin Keplerian disk with power-law temperature and column density profiles with
a projected rotational velocity of $\sim$60--75 km s$^{-1}$ and a gas
temperature of $\sim$3500 K at the innermost annulus can reproduce the CO
overtone band emission. Na I and Ca I emission lines also arise from this disk,
but they show complicated line features possibly affected by photospheric
absorption lines. Multi-epoch observations show asymmetric variations of the
line profiles on one-year (CO overtone bandhead and atomic lines for IRAS
03445+3242) or on one-day (atomic lines for IRAS 04239+2436) time scales,
implying non-axisymmetric features in disks. The narrow CO rovibrational
absorption spectra ($v$=0$\rightarrow$2) indicate that both warm ($>$ 150 K)
and cold ($\sim$20--30 K) CO gas are present along the line of sight to the
inner disk. This study demonstrates the power of IGRINS as a tool for studies
of the sub-AU scale hot and AU-scale warm protoplanetary disks with its
simultaneous coverage of the full H and K bands with high spectral resolution
($R$= 45,000) allowing many aspects of the sources to be investigated at once.
