The Central Star of NGC 2346 as a Clue to Binary Evolution through the
  Common Envelope Phase
  We present an analysis of the binary central star of the planetary nebula NGC
2346 based on archival data from the International Ultraviolet Explorer (IUE),
and new low- and high-resolution optical spectra (3700 - 7300{\AA}). By
including in the spectral analysis the contribution of both stellar and nebular
continuum, we reconciled long-time discrepant UV and optical diagnostics and
derive $E(B-V)=0.18\pm0.01$. We re-classified the companion star as A5IV by
analyzing the wings of the Balmer absorption lines in the high-resolution
($R=67\,000$) optical spectra. Using the distance to the nebula of 1400 pc from
Gaia DR2, we constructed a photoionization model based on abundances and line
intensities derived from the low-resolution optical spectra, and obtained a
temperature of $T_{\rm eff}=130\,000$K and a luminosity $L=170$L$_\odot$ for
the ionizing star, consistent with the UV continuum. This analysis allows us to
better characterize the binary system's evolution. We conclude that the
progenitor star of NGC 2346 has experienced a common envelope phase, in which
the companion star has accreted mass and evolved off the main-sequence.
