J/A+A/711/A262ivo://CDS.VizieR/J/A+A/711/A262CDSLiu J.Wang X.Chen L.Filippenko A.V.Brink T.G.Zheng W.,Pastorello A.Ochner P.Albanese I.Reguitti A.Valerin G.,Cai Y.Zhang J.Li L.Wang Z.Liu L.Zhang Y.2026-07-21T08:10:01Z2026-07-21T09:08:11ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frsupernovaephotometryvisible-astronomyultraviolet-astronomyWe present and analyze photometric and spectroscopic observations of the Type Ia supernova (SN Ia) 2024igg, another super-Chandrasekhar (or 03fg-like) SN whose strong CII{lambda}6580 feature was initially misidentified as H{alpha}, thereby constraining its progenitor system, explosion parameters, and physical scenario. We conducted a comparative analysis of SN 2024igg and other 03fg-like SNe. The radiative-transfer code TARDIS was run to identify the features in the first spectrum at t~-13.9 days. A pseudo-bolometric light curve was constructed using ultraviolet and optical photometry and was then modeled with fitting tools. SN 2024igg shows many characteristics in common with other 03fg-like objects, such as high ultraviolet flux, slowly declining light curves ({DELTA}m_15_(B)=0.90+/-0.08mag), low expansion velocities, and strong and persistent CII absorption. On the other hand, it exhibits some remarkable properties within this subgroup, including a moderately low optical luminosity (Mmax(B)=-18.99+/-0.15mag), a rise time shorter than 18.5 days, and the strongest CII{lambda}6580 ever detected. The bolometric analysis yields a ^56^Ni mass of M_Ni_=0.547+/-.082M_{sun}_ and an ejecta mass of 1.54^+0.22^_-0.19_M_{sun}_, which marginally exceeds the Chandrasekhar mass. Our TARDIS result indicates that most of the features in the earliest spectrum might be attributed to CII, which is consistent with a model in which an SN explodes within a carbon-rich circumstellar medium (CSM). The CSM interaction would produce a density peak in the ejecta, offering a natural explanation for the slowly evolving line velocities near ~8000km/s. The CSM may stem from the debris of a secondary white dwarf in a white dwarf merger or the envelope of an asymptotic giant branch star. Combined with the unshifted forbidden lines in the spectrum taken at t~+135 days, we suggest that SN 2024igg comes from a symmetric explosion on a secular timescale after the merger.2026A&A...711A.262Lhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/711/A262CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/711/A262https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/711/A262http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/711/A262https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/711/A262https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/711/A262http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/711/A262GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapUVOpticaldefaultJ/A+A/711/A262/tablea2Photometric observations of SN 2024iggrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMJDModified Julian Date, JD-2400000.5dtime.epochdoublemagObserved apparent magnitude in Filtermagphot.magfloate_magUncertainty of the magnitude measurementmagstat.error;phot.magfloatFilterPhotometric filter used for the observation (1)instr.setup;instr.filtercharSourceSource of the photometrymeta.id;instrchar