  From an analysis of absorption lines in the high resolution spectra we have
derived the radial velocities, stellar parameters (Teff, gravity, wind-strength
parameter logQ and projected rotational velocity) and abundances (C, N, O, and
Si ) of IRAS 17460-3114, IRAS 18131-3008, IRAS 19336-0400, LSE 45 and LSE 163.
Abundances are found to be solar, except for a low Si abundance in IRAS
19336-0400 and a mild CNO pattern in LSE 163, that rotates at an unusual large
rotational velocity for its spectral classification. Combining the stellar
parameters information with Gaia DR2 data we are able to derive absolute
magnitudes, radii and luminosities and clarify the possible post-AGB nature of
the objects. IRAS 17460-3114 and IRAS 18131-3008 are found to be massive OB
stars, whereas IRAS 19336-0400 is found to be a post-AGB star, already showing
nebular lines in the spectrum. However, we could not confirm the nature of LSE
45 and LSE 163 as post-AGB stars, although their parameters are much more
inconsistent with those of massive stars. In both cases, we find a discrepancy
between the spectroscopic mass and that derived from the predictions of
post-AGB evolutionary tracks. In addition, LSE 45 lacks nebular lines, that are
present in IRAS 19336-0400 at a similar temperature. In the case of LSE 163 the
rotational velocity (259+/-15 km/s) would be extremely large for a star
evolving to CSPN. The combination of this rotational velocity, the high
Galactic latitude, slightly large radial velocity and mild CNO enhancement
suggests a history of binary interaction.
