Photometric Investigation of the Unclassified Optical Transient AT 2026aaen: Discovery of a Low-Surface-Brightness Dwarf Host Galaxy

Abstract

We report the comprehensive photometric characterization of the unclassified optical transient AT 2026aaen, discovered by the Zwicky Transient Facility (ZTF) on September 1, 2026 (MJD 61275.1). Deep spatial cross-matching using high-resolution archival data from the DESI Legacy Imaging Surveys (DR10) reveals a highly diffuse, previously uncataloged Low-Surface-Brightness (LSB) dwarf galaxy directly coincident with the transient’s precise coordinates (RA = 17:08:11.087, DEC = +55:42:55.26). Multi-band follow-up photometry compiled over a 9-day baseline from ZTF, Pan-STARRS 2, and WFST shows a steady magnitude rise from an initial discovery brightness of 19.26 mag, followed by a plateau phase at approximately 19.15 mag. The combination of a slow, well-sampled light curve rise and its localization within an isolated LSB dwarf structure strongly implies a cataclysmic origin, consistent with either a thermonuclear (Type Ia) or a core-collapse supernova event. This study provides the baseline constraints on the transient prior to official spectroscopic classification on the Transient Name Server (TNS).