LHS 1815b: The First Thick-Disk Planet Detected By TESS
  We report the first discovery of a thick-disk planet, LHS 1815b (TOI-704b,
TIC 260004324), detected in the TESS survey. LHS 1815b transits a bright (V =
12.19 mag, K = 7.99 mag) and quiet M dwarf located $ 29.87\pm0.02 pc$ away with
a mass of $0.502\pm0.015 M_{\odot}$ and a radius of $0.501\pm0.030 R_{\odot}$.
We validate the planet by combining space and ground-based photometry,
spectroscopy, and imaging. The planet has a radius of $1.088\pm 0.064
R_{\oplus}$ with a $3 \sigma$ mass upper-limit of $8.7 M_{\oplus}$. We analyze
the galactic kinematics and orbit of the host star LHS1815 and find that it has
a large probability ($P_{thick}/P_{thin} = 6482$) to be in the thick disk with
a much higher expected maximal height ($Z_{max} = 1.8 kpc$) above the Galactic
plane compared with other TESS planet host stars. Future studies of the
interior structure and atmospheric properties of planets in such systems using
for example the upcoming James Webb Space Telescope (JWST), can investigate the
differences in formation efficiency and evolution for planetary systems between
different Galactic components (thick and thin disks, and halo).
