Searching for Surviving Companion in the Young SMC Supernova Remnant 1E
  0102.2-7219
  1E 0102.2--7219 (hereafter E0102) is a young supernova remnant (SNR) in the
Small Magellanic Cloud (SMC). It contains oxygen-rich SN ejecta, a possible
neutron star (NS), and a small amount of fast-moving H-rich ejecta material.
These properties are also seen in Cas A, it has thus been suggested that E0102
is also a Type IIb SNR, whose SN progenitor's hydrogen envelope was stripped
off possibly via interactions with a companion star. To search for a surviving
companion of E0102's SN progenitor, we have used archival Hubble Space
Telescope (HST) continuum images to make photometric measurements of stars
projected in the SNR to construct color-magnitude diagrams and compare the
stars with those expected from surviving companions of Type IIb SNe. We have
also used the Multi-Unit Spectroscopic Explorer observations taken with the
Very Large Telescope to perform spectroscopic analyses of stars and search for
peculiar radial velocities as diagnostics of surviving companions. We further
use the HST and Gaia data to inspect proper motions of stars for complementary
kinetic studies. No plausible companion candidates are found if the SN
explosion site was near the NS, while the B3 V star 34a may be a plausible
companion candidate if the SN explosion site is near the SN ejecta's expansion
center. If the NS is real and associated with E0102, it needs a ~1000 km/s
runaway velocity, which has been observed in other SNRs and can be acquired
from an asymmetric SN explosion or a kick by the SN explosion of a massive
companion.
