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Abstract Flares produced following the tidal disruption of stars by supermassive black holes can reveal the properties of the otherwise dormant majority of black holes and the physics of accretion. In the past decade, a class of optical-ultraviolet tidal disruption flares has been discovered whose emission properties do not match theoretical predictions. This has led to extensive efforts to model the dynamics and emission mechanisms of optical-ultraviolet tidal disruptions in order to establish them as probes of supermassive black holes. Here we present the optical-ultraviolet tidal disruption event AT 2022dbl, which showed a nearly identical repetition 700 days after the first flare. Ruling out gravitational lensing and two chance unrelated disruptions, we conclude that at least the first flare represents the partial disruption of a star, possibly captured through the Hills mechanism. Since both flares are typical of the optical-ultraviolet class of tidal disruptions in terms of their radiated energy, temperature, luminosity, and spectral features, it follows that either the entire class are partial rather than full stellar disruptions, contrary to the prevalent assumption, or some members of the class are partial disruptions, having nearly the same observational characteristics as full disruptions. Whichever option is true, these findings could require revised models for the emission mechanisms of optical-ultraviolet tidal disruption flares and a reassessment of their expected rates. 

Abstract. Expedition 364 was a joint IODP and ICDP mission-specific platform (MSP)expedition to explore the Chicxulub impact crater buried below the surface ofthe Yucatán continental shelf seafloor. In April and May 2016, thisexpedition drilled a single borehole at Site M0077 into the crater's peakring. Excellent quality cores were recovered from ∼505 to ∼1335mbelow seafloor (mb.s.f.), and high-resolution open hole logs were acquiredbetween the surface and total drill depth. Downhole logs are used to imagethe borehole wall, measure the physical properties of rocks that surround theborehole, and assess borehole quality during drilling and coringoperations. When making geological interpretations of downhole logs, it isessential to be able to distinguish between features that are geological andthose that are operation-related. During Expedition 364 some drilling-inducedand logging-related features were observed and include the following: effects caused by thepresence of casing and metal debris in the hole, logging-tool eccentering,drilling-induced corkscrew shape of the hole, possible re-magnetization oflow-coercivity grains within sedimentary rocks, markings on the boreholewall, and drilling-induced changes in the borehole diameter andtrajectory.