NGC 1980 is not a foreground population of Orion: Spectroscopic survey
  of young stars with low extinction in Orion A
  We perform a spectroscopic survey of the foreground population in Orion A
with MMT/Hectospec. We use these data, along with archival spectroscopic data
and photometric data, to derive spectral types, extinction values, and masses
for 691 stars. Using the Spitzer Space Telescope data, we characterize the disk
properties of these sources. We identify 37 new transition disk (TD) objects,
one globally depleted disk candidate, and 7 probable young debris disks. We
discover an object with a mass less than 0.018-0.030 M$_{\odot}$, which harbors
a flaring disk. Using the H$\alpha$ emission line, we characterize the
accretion activity of the sources with disks, and confirm that fraction of
accreting TDs is lower than that of optically thick disks (46$\pm$7% versus
73$\pm$9%, respectively). Using kinematic data from the Sloan Digital Sky
Survey and APOGEE INfrared Spectroscopy of Young Nebulous Clusters program
(IN-SYNC), we confirm that the foreground population shows similar kinematics
to their local molecular clouds and other young stars in the same regions.
Using the isochronal ages, we find that the foreground population has a median
age around 1-2 Myr, which is similar to the one of other young stars in Orion
A. Therefore, our results argue against the presence of a large and old
foreground cluster in front of Orion A.
