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

TL;DR

This study analyzes the nebular phase of SN 2024ggi, a nearby Type II supernova, revealing a low-mass progenitor, symmetrical ejecta, and no signs of interaction, through optical spectroscopy and photometry.

Contribution

It provides the first detailed nebular phase analysis of SN 2024ggi, estimating its progenitor mass and ejecta properties using spectral and photometric data.

Findings

Progenitor mass estimated between 12-15 solar masses.

Synthesized nickel mass around 0.05-0.06 solar masses.

Ejecta appear roughly symmetrical with minor asymmetries.

Abstract

Context: SN 2024ggi is a Type II supernova (SN) discovered in the nearby galaxy NGC 3621 (D $\approx6.7\pm0.d$ Mpc) on 2024 April 03.21 UT. Its proximity enabled 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. Aims: 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. Methods: We present 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 $uBVgri$-band photometry spanning $320-400$ days. The analysis of the nebular emission features is performed to probe ejecta asymmetries. Based on the [O I] flux and [O I]/[Ca II] ratio, and comparisons with spectra models from the literature, we arrive to an estimate of the progenitor mass. Additionally, we construct the bolometric light curve from optical photometry and near-infrared data to derive the synthesized nickel mass. Results: Our analysis suggests a progenitor zero-age-main-sequence mass between $12-15 M_\odot$. The late-time bolometric light curve is consistent with a synthesized $^{56}$Ni mass of $0.05-0.06 M_\odot$. The line profiles exhibit only minor changes over the observed period and suggest a roughly symmetrical ejecta, with a possible clump of oxygen-rich material moving towards the observer. No signatures of circumstellar material interaction are detected up to 400 days after the explosion.