J/ApJ/881/87ivo://CDS.VizieR/J/ApJ/881/87doi:10.26093/cds/vizier.18810087CDSGomez+Gomez S.Berger E.Nicholl M.Blanchard P.K.Villar V.A.,Patton L.Chornock R.Leja J.Hosseinzadeh G.Cowperthwaite P.S.2021-12-06T23:31:42Z2021-01-08T12:12:18ZCDS support team

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

cds-question@unistra.frsupernovaevisible-astronomyspectroscopyWe present optical photometry and spectroscopy of SN2016iet (=Gaia16bvd=PS17brq), an unprecedented Type I supernova (SNI) at z=0.0676 with no obvious analog in the existing literature. SN2016iet exhibits a peculiar light curve, with two roughly equal brightness peaks (~-19mag) separated by about 100 days, and a subsequent slow decline by about 5mag in 650 rest-frame days. The spectra are dominated by strong emission lines of calcium and oxygen, with a width of only 3400km/s, superposed on a strong blue continuum in the first year. There is no clear evidence for hydrogen or helium associated with the SN at any phase. The nebular spectra exhibit a ratio of L_CaII_/L_OI_~4, much larger than for core-collapse SNe and TypeI superluminous SNe. We model the light curves with several potential energy sources: radioactive decay, a central engine, and ejecta-circumstellar medium (CSM) interaction. Regardless of the model, the inferred progenitor mass near the end of its life (i.e., the CO core mass) is >~55M{sun} and potentially up to 120M{sun}, clearly placing the event in the regime of pulsational pair instability supernovae (PPISNe) or pair instability supernovae (PISNe). The models of CSM interaction provide the most consistent explanation for the light curves and spectra, and require a CSM mass of ~35M{sun} ejected in the final decade before explosion. We further find that SN2016iet is located at an unusually large projected offset (16.5kpc, 4.3 effective radii) from its low-metallicity dwarf host galaxy (Z~0.1Z{sun}, L~0.02L*, M~108.5M{sun}), supporting the interpretation of a PPISN/PISN explosion. In our final spectrum at a phase of about 770 rest-frame days we detect weak and narrow H{alpha} emission at the location of the SN, corresponding to a star formation rate of ~3x10^-4^M{sun}/yr, which is likely due to a dim underlying galaxy host or an HII region. Despite the overall consistency of the SN and its unusual environment with PPISNe and PISNe, we find that the inferred properties of SN2016iet challenge existing models of such events.2019ApJ...881...87Ghttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/881/87CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/ApJ/696/870 : Catalina Real-time Transient Survey (CRTS) (Drake+, 2009)J/ApJ/742/89 : Relations between spectra and colors of SNe Ia (Foley+, 2011)J/ApJ/745/74 : Pre-maximum spectra of type Ia SNe (Folatelli+, 2012)J/ApJ/759/107 : Core-collapse SNe and host galaxies (Kelly+, 2012)J/ApJ/793/38 : Palomar Transient Factory photometric obs. (Arcavi+, 2014)J/ApJ/785/37 : Type Ic SN 2010mb optical photometry (Ben-Ami+, 2014)J/ApJ/794/23 : Pan-STARRS1 transients optical photometry (Drout+, 2014)J/A+A/573/A2 : SN 2012Z spectra (Stritzinger+, 2015)J/A+A/573/A12 : SN1993J spectr 100to500 days post-explosion (Jerkstrand+, 2015)J/ApJ/832/108 : Spectral properties of Type Ic & Ic-bl SNe (Modjaz+, 2016)J/A+A/602/A93 : SN Type Ibn OGLE-2014-SN-131 lightcurves (Karamehmetoglu+,2017)J/ApJ/836/60 : Bgri light curves of PTF11kmb and PTF12bho (Lunnan+, 2017)J/ApJ/835/58 : PTF 12dam & iPTF 13dcc follow-up (Vreeswijk+, 2017)J/ApJ/853/62 : Optical and NIR spectra and LCs of SN2016ija (Tartaglia+, 2018)J/ApJ/854/L14 : Photometry and spectra of SN 2017dio (Kuncarayakti+, 2018)J/ApJ/863/109 : Follow-up optical obs. of the SNIc SN2014L (Zhang+, 2018)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/881/87https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/881/87http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/881/87https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/881/87https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/881/87http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/881/87GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/ApJ/881/87/fig4Combined table from original tablesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMJDModified Julian Date of observationdtime.epochcharwaveSpectrum wavelength, Angstroms0.1nmem.wldoublefluxSpectrum flux, erg/cm2/s/{AA}10mW.m**-2.nm**-1phot.fluxdouble