We present multiband photometric and spectroscopic observations of supernova (SN) 2024abvb, which exhibits early-time prominent photoionized narrow emission lines of C II superposed on a blue continuum. The absence of Balmer features indicates that the SN exploded within hydrogen-poor circumstellar matter (CSM). Together with the lack of explicit evidence of helium signatures, we tentatively identify SN 2024abvb as a Type Icn SN (SN Icn). After correcting for extinction, we estimate an r-band peak absolute magnitude of -19.7, placing SN 2024abvb in the luminous regime of SNe Icn. We adopted a hybrid model that accounts for both the energy released by the ejecta-CSM interaction and the radioactive decay of nickel synthesized in the SN ejecta to fit the light curve of SN 2024abvb. The best-fit model to the multiband light curves within the first ~ 40 days after explosion suggests that the CSM, radioactive nickel, and ejecta masses to be 0.28 Msun, < 3.8 * 10^-2 Msun, and 0.12 Msun, respectively. Such a low ejecta mass indicates that the progenitor star of SN 2024abvb experienced a significant mass-stripping process, consistent with the hydrogen-poor and helium-poor spectral features. SN 2024abvb provides important insights into the physical origins of the rare subclass of SNe Icn.
@article{arxiv.2601.01333,
title = {SN 2024abvb: A Type Icn Supernova in the Outskirts of its Host Galaxy},
author = {Maokai Hu and Shengyu Yan and Xiaofeng Wang and Abdusamatjan Iskandar and Jujia Zhang and Liping Li and Ali Esamdin and Letian Wang and Lingzhi Wang and Alexei V. Filippenko and Thomas G. Brink and Liyang Chen and Ruifeng Huang and Lifan Wang},
journal= {arXiv preprint arXiv:2601.01333},
year = {2026}
}