The GALAH Survey: Improving our understanding of confirmed and candidate
  planetary systems with large stellar surveys
  Pioneering photometric, astrometric, and spectroscopic surveys are helping
exoplanetary scientists better constrain the fundamental properties of stars
within our galaxy, and the planets these stars host. In this study, we use the
third data release from the stellar spectroscopic GALAH Survey, coupled with
astrometric data of eDR3 from the \textit{Gaia} satellite, and other data from
NASA's Exoplanet Archive, to refine our understanding of 279 confirmed and
candidate exoplanet host stars and their exoplanets. This homogenously analysed
data set comprises 105 confirmed exoplanets, along with 146 K2 candidates, 95
TESS Objects of Interest (TOIs) and 52 Community TOIs (CTOIs). Our analysis
significantly shifts several previously (unknown) planet parameters while
decreasing the uncertainties for others; Our radius estimates suggest that 35
planet candidates are more likely brown dwarfs or stellar companions due to
their new radius values. We are able to refine the radii and masses of WASP-47
e, K2-106 b, and CoRoT-7 b to their most precise values yet, to less than 2.3\%
and 8.5\% respectively. We also use stellar rotational values from GALAH to
show that most planet candidates will have mass measurements that will be tough
to obtain with current ground-based spectrographs. With GALAH's chemical
abundances, we show through chemo-kinematics that there are five planet-hosts
that are associated with the galaxy's thick disc, including NGTS-4, K2-183 and
K2-337. Finally, we show there is no statistical difference between the
chemical properties of hot Neptune and hot rocky exoplanet hosts, with the
possibility that short-period rocky worlds might be the remnant cores of
hotter, gaseous worlds.
