  Context: Few exoplanets around hot stars with radiative envelopes have been
discovered, although new observations from the TESS mission are improving this.
Stars with radiative envelopes have little mixing at their surface, and thus
their surface abundances provide a sensitive test case for a variety of
processes including potentially star-planet interactions. Atomic diffusion is
particularly important in these envelopes, producing chemically peculiar
objects such as Am and HgMn stars. Aims: An exoplanet candidate around the B6
star HD 235349 was identified by TESS. Here we determine the nature of this
transiting object and identify possible chemical peculiarities in the star.
Methods: HD 235349 was observed using the long-slit spectrograph at Tartu
Observatory, as well as photometrically by the TESS mission. The spectra were
modeled to determine stellar parameters and chemical abundances. The
photometric light curve was then analyzed in the context of the stellar
parameters to determine properties of the transiting object. Results: We find
the transiting object is a low-mass stellar companion, not a planet. However,
the primary of this eclipsing binary is a rare type of chemically peculiar
star. A strong overabundance of P is found with overabundances of Ne and Nd,
and mild overabundances of Ti and Mn, while He is mildly underabundant. There
is also clear evidence for vertical stratification of P in the atmosphere of
the star. The lack of Hg and weak Mn overabundance suggests that this is not a
typical HgMn star. It may be in the class of helium-weak phosphorus-gallium
(He-weak PGa) stars, or an intermediate between these two classes. Conclusions:
We show that HD 235349 is a rare type of chemically peculiar star (He-weak PGa)
in an eclipsing binary system with a low-mass stellar companion. This appears
to be the first He-weak PGa star discovered in an eclipsing binary.
