J/ApJ/902/139ivo://CDS.VizieR/J/ApJ/902/139doi:10.26093/cds/vizier.19020139CDSKuncarayakti H.Folatelli G.Maeda K.Dessart L.Jerkstrand A.,Anderson J.P.Aoki K.Bersten M.C.Ferrari L.Galbany L.Garcia F.,Gutierrez C.P.Hattori T.Kawabata K.S.Kravtsov T.Lyman J.D.,Mattila S.F.O. ESanchez S.F.Van Dyk S.D.2022-09-07T13:10:26Z2022-05-12T09:35:55ZCDS support team

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

cds-question@unistra.frvisible-astronomyspectroscopysupernovaeSpectral observations of the type-IIb supernova (SN) 2016gkg at 300-800 days are reported. The spectra show nebular characteristics, revealing emission from the progenitor star's metal-rich core and providing clues to the kinematics and physical conditions of the explosion. The nebular spectra are dominated by emission lines of [OI]{lambda}{lambda}6300,6364 and [CaII]{lambda}{lambda}7292,7324. Other notable, albeit weaker, emission lines include MgI] {lambda}4571, [FeII]{lambda}7155, OI{lambda}7774, CaII triplet, and a broad, boxy feature at the location of H{alpha}. Unlike in other stripped-envelope SNe, the [OI] doublet is clearly resolved due to the presence of strong narrow components. The doublet shows an unprecedented emission line profile consisting of at least three components for each [OI]{lambda}6300,6364 line: a broad component (width ~2000km/s), and a pair of narrow blue and red components (width ~300km/s) mirrored against the rest velocity. The narrow component appears also in other lines, and is conspicuous in [OI]. This indicates the presence of multiple distinct kinematic components of material at low and high velocities. The low-velocity components are likely to be produced by a dense, slow-moving emitting region near the center, while the broad components are emitted over a larger volume. These observations suggest an asymmetric explosion, supporting the idea of two-component ejecta that influence the resulting late-time spectra and light curves. SN 2016gkg thus presents striking evidence for significant asymmetry in a standard-energy SN explosion. The presence of material at low velocity, which is not predicted in 1D simulations, emphasizes the importance of multidimensional explosion modeling of SNe.2020ApJ...902..139Khttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/902/139CatalogResearchIsServedByTAP VizieR generic servicerelated-toVIII/73 : HI Parkes All Sky Survey Catalogue (HIPASS) (Meyer+, 2004)J/MNRAS/372/1315 : UBVRI photometry of SN 2004et (Sahu+, 2006)J/MNRAS/416/3138 : SN 2009jf light curves (Valenti+, 2011)J/A+A/559/A114 : Updated O3N2 and N2 abundance indicators (Marino+, 2013)J/ApJ/785/37 : Type Ic SN 2010mb optical photometry (Ben-Ami+, 2014)J/MNRAS/442/844 : BVRI light curves of type II-P supernovae (Faran+, 2014)J/A+A/580/A142 : SN 2011dh. The first two years (Ergon+, 2015)J/A+A/573/A12 : SN1993J spectra 100-500d post-explosion (Jerkstrand+, 2015)J/ApJ/854/L14 : Photometry and spectra of SN 2017dio (Kuncarayakti+, 2018)J/ApJ/885/43 : UBVRI & ugriz phot. of supernova SN 2017gmr (Andrews+, 2019)J/ApJ/873/L3 : NUV to NIR photometry of type IIP ASASSN-16at (Bose+, 2019)J/AJ/159/167 : AMUSING++ nearby galaxy compilation. I. (Lopez-Coba+, 2020)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/902/139https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/902/139http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/902/139https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/902/139https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/902/139http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/902/139GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/ApJ/902/139/fig1Nebular spectra of SN 2016gkgrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintInstInstrument identifier (1)meta.id;instrcharPhase[320/764] Days after maximumtime.intervalintlambda[4458.68/9303.71] Wavelength in Angstrom units0.1nmem.wldoubleRFlux[-798.2/16259.3] Relative flux; in 10^-20^erg/s/cm^2^/{AA} units1e-20cW.m**-2.nm**-1meta.unitdouble