Extragalactic fast X-ray transient cand.

We extend the search for extragalactic FXTs from Quirola et al. 2022 (Paper I; based on sources in the Chandra Source Catalog 2.0, CSC2, using data taken between 2000-2014) to further Chandra archival data between 2014-2022. We extract X-ray data using a method similar to that employed by CSC2 and apply identical search criteria as in Paper I (Quirola et al., 2022A&A...663A.168Q).

We report the detection of eight FXT candidates, with peak 0.3-10keV fluxes between 1*10^-13^ to 1*10^-11^erg/cm^2^/s and T90 values from 0.3 to 12.1ks. This sample of FXTs has likely redshifts between 0.7 to 1.8. Three FXT candidates exhibit light curves with a plateau (~1-3ks duration) followed by a power-law decay and X-ray spectral softening, similar to what was observed for a few previously reported FXTs in Paper I. In light of the new, expanded source lists (eight FXTs with known redshifts from Paper I and this work), we update the event sky rates derived in Paper I, finding 36.9^+9:7^_-8.3_deg^2^*yr^-1^ for the extragalactic samples for a limiting flux of >~1*10^-13^erg/cm^2^/s, calculate the first FXT X-ray luminosity function, and compare the volumetric density rate between FXTs and other transient classes.