The nebular phase of SN 2024ggi: A low-mass progenitor with no signs of interaction

Abstract

<p><b>Context</b><br></p><p><em></em>SN 2024ggi is a Type II supernova (SN) discovered in the nearby galaxy NGC 3621 (D ≈ 6.7 ± 0.4 Mpc) on 2024 April 03.21 UT. Its proximity has prompted a detailed investigation of the SN’s properties and its progenitor star. This work focuses on the optical evolution of SN 2024ggi at the nebular phase.</p><p><b>Aims</b><br></p><p><em></em>We investigate the progenitor properties and possible asymmetries in the ejecta by studying the nebular phase evolution between days 287 and 400 after the explosion.</p><p><b>Methods</b><br></p><p><em></em>We present the optical photometry and spectroscopy of SN 2024ggi during the nebular phase, obtained with the Las Campanas and Gemini South Observatories. Four nebular spectra were taken at 287, 288, 360, and 396 days post-explosion, supplemented by late-time <em>uBVgri</em>-band photometry spanning 320–400 days. The analysis of the nebular emission features was performed to probe the ejecta asymmetries. Based on the [O I] flux and [O I]/[Ca II] ratio, coupled with comparisons with spectra models from the literature, we arrived at an estimate of the progenitor mass. Additionally, we constructed the bolometric light curve from optical photometry and near-infrared data to derive the synthesized nickel mass.</p><p><b>Results</b><br></p><p>Our analysis suggests a progenitor zero-age main sequence mass between 12 − 15 <em>M</em>_⊙. The late-time bolometric light curve is consistent with a synthesized ⁵⁶Ni mass of 0.05 − 0.06 <em>M</em>_⊙. The line profiles exhibit only minor changes over the observed period, suggesting roughly symmetrical ejecta, with a possible clump of oxygen-rich material moving towards the observer. There were no signatures of circumstellar material interaction detected up to 400 days after the explosion.</p>