J/A+A/694/A292ivo://CDS.VizieR/J/A+A/694/A292doi:10.26093/cds/vizier.36940292CDSGkini A.Fransson C.Lunnan R.Schulze S.Poidevin F.Sarin N.,Konyves-Toth R.Sollerman J.Omand C.M.B.Brennan S.J.Hinds K.R.,Anderson J.P.Bronikowski M.Chen T.-W.Dekany R.Fraser M.,Fremling C.Galbany L.Gal-Yam A.Gangopadhyay A.Geier S.,Gonzalez E.P.Gromadzki M.Groom S.L.Gutierrez C.P.Hiramatsu D.,Howell D.A.Hu Y.Inserra C.Kopsacheili M.Lacroix L.Masci F.J.,Matilainen K.McCully C.Moore T.Muller-Bravo T.E.Nicholl M.,Pellegrino C.Perez-Fournon I.Perley D.A.Pessi P.J.Petrushevska T.,Pignata G.Ragosta F.Sahu A.Singh A.Srivastav S.Wise J.L.Yan L.,Young D.R.2025-05-21T20:02:01Z2025-02-24T11:41:27ZCDS support team

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

cds-question@unistra.frsupernovaephotometryvisible-astronomyWe present photometric and spectroscopic observations of SN 2020xga and SN 2022xgc, two hydrogen-poor superluminous supernovae (SLSNe-I) at z=0.4296 and z=0.3103 respectively, that show an additional set of broad Mgii absorption lines, blueshifted by a few thousands km s~1 with respect to the host galaxy absorption system. Previous work interpreted this as due to resonance line scattering of the SLSN continuum by rapidly expanding CSM expelled shortly before the explosion. The peak rest-frame g-band magnitude of SN 2020xga is ~22.30+/-0.04mag and of SN 2022xgc is ~21.97+/-0.05mag, placing them among the brightest SLSNe-I. We use high-quality spectra from ultraviolet to near-infrared wavelengths to model the Mgii line profiles and infer the properties of the CSM shells. We find that the CSM shell of SN 2020xga resides at ~1.3x10^16^cm moving with a maximum velocity of 4275 km s~1, and the shell of SN 2022xgc is located at ~0.8x10^16^cm reaching up to 4400km/s. These shells were expelled ~11 and ~5 months before explosion for SN 2020xga and SN 2022xgc respectively, possibly as a result of Luminous Blue Variable-like eruptions or pulsational pair instability (PPI) mass loss. We also analyze optical photometric data and model the light curves considering powering from the magnetar spin-down mechanism. The results support very energetic magnetars, approaching the masss-hedding limit, powering these SNe with ejecta masses of ~7-9M_{sun}_. The ejecta masses inferred from the magnetar modeling are not consistent with the PPI scenario pointing towards stars >50M_{sun}_ He-core, hence alternative scenarios such as fallback accretion are discussed. Modeling the spectral energy distribution of the host galaxy of SN 2020xga reveals a host mass of 10^7.8^M_{sun}_, a star formation rate of 0.96^+0.47^_-0.26_M_{sun}_/yr, and a metallicity of ~0.2Z_{sun}_.2025A&A...694A.292Ghttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/694/A292CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/694/A292https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/694/A292http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/694/A292https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/694/A292https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/694/A292http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/694/A292GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/A+A/694/A292/2020xgaPhotometric data of SN 2020xgaPhasePhasedtime.phasefloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMJDModified Julian datedtime.epochfloatFilter[grizco] Filterinstr.bandpasscharmagMagnitude in Filter (AB) (1)magphot.magfloate_magMagnitude in Filter (AB) errormagstat.error;phot.magfloatInstInstrumentmeta.id;instrcharJ/A+A/694/A292/2022xgcPhotometric data of SN 2022xgcrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMJDModified Julian datedtime.epochfloatPhasePhasedtime.phasefloatFilter[grizco] Filterinstr.bandpasscharmagMagnitude in Filter (AB) (1)magphot.magfloate_magMagnitude in Filter (AB) errormagstat.error;phot.magfloatInstInstrumentmeta.id;instrchar