AT 2023clx: The Faintest and Closest Optical Tidal Disruption Event Discovered in Nearby Star-forming Galaxy NGC 3799

We report the discovery of a faint optical tidal disruption event (TDE) in the nearby star-forming galaxy NGC 3799. Identification of the TDE is based on its position at the galaxy nucleus, a light curve declining as t ^‑5/3, a blue continuum with an almost constant blackbody temperature of ∼12,000 K, broad (≈15,000 km s^‑1) Balmer lines, and characteristic He II 4686 Å emission. The light curve of AT 2023clx peaked at an absolute magnitude of ‑17.16 mag in the g band and a maximum blackbody bolometric luminosity of 4.56 × 10⁴² erg s^‑1, making it the faintest TDE discovered to date. With a redshift of 0.01107 and a corresponding luminosity distance of 47.8 Mpc, it is also the closest optical TDE ever discovered to the best of our knowledge. Furthermore, our analysis of Swift/XRT observations of AT 2023clx yields a very tight 3σ upper limit of 9.53 × 10³⁹ erg s^‑1 in the range 0.3–10 keV. AT 2023clx, together with very few other faint TDEs such as AT 2020wey, prove that there are probably a large number of faint TDEs yet to be discovered at higher redshifts, which is consistent with the prediction of luminosity functions (LFs). The upcoming deeper optical time-domain surveys, such as the Legacy Survey of Space and Time and the Wide Field Survey Telescope, will discover more TDEs at even lower luminosities, allowing for a more precise constraint of the low end of the LF.