eROSITA-RU Tidal Disruption Events with Keck-I/LRIS: Sample Selection, Optical Properties, and Host Galaxy Demographics

We present an optical spectroscopic study of 70 soft X-ray–selected TDE candidates discovered by the eROSITA-RU all-sky survey. For each event, we determine a statistically robust host-galaxy association and obtain Keck-I/LRIS spectra for all host galaxies. We combine broad-band photometry and optical spectroscopy in a joint, nonparametric SED modeling framework using Prospector, and we measure stellar continua and emission-line properties with pPXF. Building on these measurements, we adopt a classification scheme that incorporates X-ray behavior, optical variability, broad-line properties, and narrow-line diagnostics. This procedure yields a sample of 52 TDEs spanning 0.018 < z < 0.714, which we further divide into 41 high-confidence “gold” events and 11 lower-confidence “silver” events. In the gold sample, most events are intrinsically X-ray bright. We identify transient spectroscopic features in eight events, including broad He II and or Hα emission as well as two coronal-line TDEs. Finally, we quantify the host-galaxy demographics using statistical test, finding modest over-representation in green-valley and quiescent Balmer-strong galaxies compared to previous TDE samples, and generally suppressed star formation relative to the star-forming main sequence, consistent with selection effects of X-ray discovery.