J/A+A/588/A1ivo://CDS.VizieR/J/A+A/588/A1doi:10.26093/cds/vizier.35880001CDSPolshaw J.Kotak R.Dessart L.Fraser M.Gal-Yam A.Inserra C.,Sim S.A.Smartt S.J.Sollerman J.Baltay C.Rabinowitz D.Benetti S.,Botticella M.T.Campbell H.Chen T.-W.Galbany L.McKinnon R.,Nicholl M.Smith K.W.Sullivan M.Takats K.Valenti S.Young D.R.2016-03-09T07:37:58Z2016-03-09T08:15:01ZCDS support team

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

cds-question@unistra.frsupernovaespectroscopyWe present optical imaging and spectroscopy of supernova (SN) LSQ13fn, a type II supernova with several hitherto-unseen properties. Although it initially showed strong symmetric spectral emission features attributable to HeII, NIII, and CIII, reminiscent of some interacting SNe, it transitioned into an object that would fall more naturally under a type II-Plateau (IIP) classification. However, its spectral evolution revealed several unusual properties: metal lines appeared later than expected, were weak, and some species were conspicuous by their absence. Furthermore, the line velocities were found to be lower than expected given the plateau brightness, breaking the SN IIP standardised candle method for distance estimates. We found that, in combination with a short phase of early-time ejecta-circumstellar material interaction, metal-poor ejecta, and a large progenitor radius could reasonably account for the observed behaviour. Comparisons with synthetic model spectra of SNe IIP of a given progenitor mass would imply a progenitor star metallicity as low as 0.1Z_{sun}_. LSQ13fn highlights the diversity of SNe II and the many competing physical effects that come into play towards the final stages of massive star evolution immediately preceding core-collapse.2016A&A...588A...1Phttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/588/A1CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/588/A1https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/588/A1http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/588/A1https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/588/A1https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/588/A1http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/588/A1GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/A+A/588/A1/tablea5Log of the spectroscopic observations of LSQ13fnrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintObs.DateObservation datetime.epoch;obsnullableMJDModified Julian datedtime.epochfloatEpochEpoch relative to the date of maximum brightness (MJD=56306.21) in the rest frame of the SNdtime.epochfloatTelTelescope + instrumentinstrcharb_lambdaWavelength range0.1nmem.wlintB_lambdaWavelength range0.1nmem.wlintExpTimeExposure time(s) in second unitmeta.unit;time.duration;obs.exposurecharSlitSlit widtharcsecspect.line.widthfloatResResolution (1)0.1nmspect.resolutionfloatRes2? Second resolution (1)0.1nmspect.resolutionfloatnullablespShow the spectrummeta.ref.urlcharFileNameName of the spectrum file in subdirectory spmeta.id;meta.filechar