As part of its commissioning, the Vera C. Rubin Observatory observed several fields repeatedly for a month with ComCam, an instrument that uses the same hardware as the LSST camera but covers a smaller field of view. We photometrically classify AT 2024ahzi, a transient discovered by ComCam, as a Type IIP supernova (SN IIP) using both ComCam and DECam photometry. We find that the duration, luminosity, and color of AT 2024ahzi's photometric plateau are all consistent with those from a large sample of SNe II. By comparing its multi-band light curves to SN II models and analytic relations, we place constraints on the SN progenitor, explosion dynamics, and circumstellar environment. We argue that the progenitor has an extended density profile indistinguishable from a slowly accelerating CSM. We discuss how a similar workflow can identify and characterize future Rubin SNe II.
@article{arxiv.2603.00262,
title = {AT 2024ahzi: A Type IIP Supernova Discovered by the LSST Commissioning Camera},
author = {Kaylee de Soto and V. Ashley Villar and Jared A. Goldberg and Anya Nugent and Yize Dong and Ryan J. Foley and Tobias Geron and Luca Izzo and C. Tanner Murphey and Katie Auchettl and David A. Coulter and Thomas de Boer and Kenneth C. Chambers and Diego A. Farias and Christa Gall and Hua Gao and Jens Hjorth and Willem B. Hoogendam and David O. Jones and Gauri Nair and Gautham Narayan and Armin Rest and Kishore C. Patra and Haille M. L. Perkins and Margaret E. Verrico and Qinan Wang and Amanda R. Wasserman and Yossef Zenat},
journal= {arXiv preprint arXiv:2603.00262},
year = {2026}
}