Nodal precession of a hot Jupiter transiting the edge of a late A-type star TOI-1518

TOI-1518b, a hot Jupiter around a late A-type star, is one of the few planetary systems that transit the edge of the stellar surface (the impact parameter $b\sim 0.9$) among hot Jupiters around hot stars (Cabot et al. 2021). The high rotation speed of the host star ($\sim 85$ km s${}^{-1}$) and the nearly polar orbit of the planet ($\sim 120$ deg) may cause a nodal precession. In this study, we report the nodal precession undergone by TOI-1518,b. This system is the fourth planetary system in which nodal precession is detected. We investigate the time change in $b$ from the photometric data of TOI-1518 acquired in 2019 and 2022 with TESS and from the spectral transit data of TOI-1518b obtained in 2020 with two high-dispersion spectrographs; CARMENES and EXPRES. We find that the value of $b$ is decreasing with $db\mathrm{/}dt=-0.0116\pm 0.0036$,year${}^{-1}$, indicating that the transit trajectory is moving toward the center of the stellar surface. We also estimate the minimum value of the quadrupole mass moment of TOI-1518 $J_{2,\mathrm{m}\mathrm{i}\mathrm{n}}=4.41\times {10}^{-5}$ and the logarithm of the Love number of TOI-1518 $\log k_2=-2.17\pm 0.33$ from the nodal precession.