AstroNote 2023-311

ZTF23abjuxso/2023vek/PS23jmv was first reported by Pan-STARRS on MJD = 60231.33. ZTF forced photometry at the location of the transient shows an earliest detection at MJD = 60203.36 at a magnitude of g = 20.926±0.176. It rose in brightness slowly, displaying a ~60 day rise, whilst remaining blue in color up to and at peak. We observed ZTF23abjuxso at MJD = 60264.91 using the SPectrograph for the Rapid Acquisition of Transients (SPRAT, Piascik et al. 2014) on the Liverpool Telescope. To optimise signal to noise, and to remove cosmic rays contaminating the spectrum, the images were cleaned using LACosmic (van Dokkum 2001) and the trace was manually extracted using a PSF-like fit. Using Superfit (Howell et al. 2005), we found a good fit to SLSN-I templates at z = 0.24-0.25, with clear OII absorption troughs visible.

We then obtained a precise redshift using a spectrum taken on the Palomar P200 Double Spectrograph (DBSP, Oke & Gunn 1982) taken at MJD = 60258.25. Close inspection revealed the presence of narrow H-alpha and [OIII]5007 emission lines from the host galaxy.