J/A+A/709/A156ivo://CDS.VizieR/J/A+A/709/A156CDSPeng Z.-H.Benetti S.Cai Y.-Z.Pastorello A.Zhao J.-W.Reguitti A.,Wang Z.-Y.Cappellaro E.Elias-Rosa N.Fang Q.-L.Fraser M.Kangas T.,Kankare E.Kostrzewa-Rutkowska Z.Lundqvist P.Mattila S.Reynolds T.M.,Stritzinger M.D.Somero A.Tomasella L.Pei S.-P.Yang Y.-J.,Zhang J.-J.Pan Y.2026-05-19T11:00:40Z2026-05-19T11:51:34ZCDS support team

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

cds-question@unistra.frsupernovaevisible-astronomysloan-photometryWe present optical photometric and spectroscopic observations of the Type IIb supernova (SN) 2017ati. It reached the maximum light at about 27~d after the explosion and the light curve shows a broad, luminous peak with an absolute r-band magnitude of M_r_=-18.48+/-0.16mag. At about 50d after maximum light, SN 2017ati exhibits a decline rate close to that expected from the ^56^Co --> ^56^Fe radioactive decay, at 0.98mag per 100-days, as usually observed in SNe IIb. However, it remains systematically brighter at late times by about 1-2mag, exceeding the usual upper luminosity range of this class. As a result, modelling the light curve of SN 2017ati with a standard ^56^Ni decay scenario requires a large nickel mass of up to ~0.37M_{sun}_ and still fails to reproduce the early-time light curve adequately. In contrast, incorporating additional energy input from a magnetar yields a significantly improved fit to the light curve of SN 2017ati, which would reduce the nickel mass to ~0.21M_{sun}_, still close to the upper end of the range typically inferred for SNe IIb. Comparing the fitted results of SN~2017ati with the known sample of SNe IIb indicates that its luminosity evolution is best explained by a combination of neutron star spin- down energy and radioactive nickel deposition. From late-time nebular spectra of SN 2017ati, the luminosity of the [OI]{lambda}{lambda}6300,6364 doublet implies an oxygen mass of ~1.82-3.34M_{sun}_, and the combination of a [CaII]/[OI] flux ratio of ~0.5 with nebular spectral model comparisons favours a progenitor zero-age main-sequence mass of >=17M_{sun}_.2026A&A...709A.156Phttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/709/A156CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/709/A156https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/709/A156http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/709/A156https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/709/A156https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/709/A156http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/709/A156GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/A+A/709/A156/tablePhotometry of SN 2017atirecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintDateDate of observation (yyyy/mm/dd)time.epochnullableMJDModified Julian Datedtime.epochdoubleFilterFilter (1)meta.id;instr.filtercharSystemSystem, AB or Vegapos.framecharl_magLimit flag on magmeta.code.errorcharmagApparent magnitude in filtermagphot.magfloate_mag? Error on apparent magnitude in filtermagstat.error;phot.magfloatnullableInstInstrument or Sourcemeta.id;instrchar