AstroNote 2026-237

Photometric observations obtained with the 1.82-m Plaskett telescope are differential (SDSS g&r filters) and measured from stars in either the Sloan Digital Sky Survey (Skyserver) or the Pan-STARRS release 1 (PS1) Survey - DR1. Observations obtained with the UBC Southern telescope are differential aperture magnitudes  in the Kron-Cousins filter system using field stars from the Tycho, UCAC, OGLE & Gaia catalogues as obtained through SIMBAD (2000,A&AS,143,9 , "The SIMBAD astronomical database", Wenger et al.) . The photometric observations are contained in an attached table (see below - OTmags_260804.txt).

The transient host galaxy light in our DAO photometric measurement is minimized via one of two methods: Reference images are downloaded from the PanSTARRS image access (Flewelling, H. A., et al.) and are convolved, using the nightly PSF to match our images. The reference is then subtracted from our co-added images. A secondary photometric standard is defined and retained on the subtracted image using a pixel mask placed upon it on the reference, thus retaining the standard in the image subtraction.

A second method involves creating a model galaxy, using the IRAF artdata packages, scaling it to the images and subtracting the host galaxy. The differential photometry  was then performed using Image Reduction and Analysis Facility (IRAF) (Tody, D. 1986, "The IRAF Data Reduction and Analysis System").

Note:  photometric redshifts of presumed host galaxies are marked 'p' and spectroscopic redshifts are marked 's'. All host redshifts are via the SDSS Skyserver.