J/ApJ/927/78ivo://CDS.VizieR/J/ApJ/927/78doi:10.26093/cds/vizier.19270078CDSDimitriadis G.Foley R.J.Arendse N.Coulter D.A.Jacobson-Galan W.V.,Siebert M.R.Izzo L.Jones D.O.Kilpatrick C.D.Pan Y.-C.Taggart K.,Auchettl K.Gall C.Hjorth J.Kasen D.Piro A.L.Raimundo S.I.,Ramirez-Ruiz E.Rest A.Swift J.J.Woosley S.E.2024-09-05T20:09:48Z2023-12-22T11:59:25ZCDS support team

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

cds-question@unistra.frsupernovaevisible-astronomyspectroscopyinfrared-photometrybroad-band-photometryultraviolet-astronomySeeing pristine material from the donor star in a type Ia supernova (SN Ia) explosion can reveal the nature of the binary system. In this paper, we present photometric and spectroscopic observations of SN2020esm, one of the best-studied SNe of the class of "super-Chandrasekhar" SNe Ia (SC SNe Ia), with data obtained -12 to +360 days relative to peak brightness, obtained from a variety of ground- and space-based telescopes. Initially misclassified as a type II supernova, SN 2020esm peaked at M_B_=-19.9mag, declined slowly ({Delta}m_15_(B)=0.92mag), and had particularly blue UV and optical colors at early times. Photometrically and spectroscopically, SN2020esm evolved similarly to other SC SNe Ia, showing the usual low ejecta velocities, weak intermediate-mass elements, and the enhanced fading at late times, but its early spectra are unique. Our first few spectra (corresponding to a phase of >~10days before peak) reveal a nearly pure carbon/oxygen atmosphere during the first days after explosion. This composition can only be produced by pristine material, relatively unaffected by nuclear burning. The lack of H and He may further indicate that SN 2020esm is the outcome of the merger of two carbon/oxygen white dwarfs. Modeling its bolometric light curve, we find an ^56^Ni mass of 1.23_-0.14_^+0.14^M_{sun}_ and an ejecta mass of 1.75_-0.20_^+0.32^M_{sun}_, in excess of the Chandrasekhar mass. Finally, we discuss possible progenitor systems and explosion mechanisms of SN 2020esm and, in general, the SC SNe Ia class.2022ApJ...927...78Dhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/927/78CatalogResearchIsServedByTAP VizieR generic servicerelated-toVII/259 : 6dF galaxy survey final redshift release (Jones+, 2009)J/AJ/137/4517 : UVOT light curves of supernovae (Brown+, 2009)J/ApJ/700/331 : Light curves of type Ia supernovae (CfA3) (Hicken+, 2009)J/MNRAS/410/585 : SN 2009dc BVRI light curves (Silverman+, 2011)J/ApJ/753/22 : Swift/UVOT observations of SN 2011fe (Brown+, 2012)J/MNRAS/425/1789 : Berkeley supernova Ia program. I. (Silverman+, 2012)J/A+A/554/A27 : 2011fe spectrophotometric time series (Pereira+, 2013)J/ApJ/795/44 : PS1 SNe Ia (0.02<z<0.7) griz light curves (Rest+, 2014)J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)J/ApJS/220/9 : CfAIR2: NIR light curves of Type Ia SNe (Friedman+, 2015)J/ApJ/826/56 : HST/WFC3 obs. of Cepheids in SN Ia host gal. (Riess+, 2016)J/ApJ/841/48 : UBVR and IR photometry of SN 2011fe (Ia) (Shappee+, 2017)J/ApJ/859/101 : The supernovae Ia Pantheon sample (Scolnic+, 2018)J/ApJ/900/140 : CSP-II: sp. of the 03fg-like SN Ia LSQ14fmg (Hsiao+, 2020)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/927/78https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/927/78http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/927/78https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/927/78https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/927/78http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/927/78GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapUVOpticalInfrareddefaultJ/ApJ/927/78/table1UVOIR bolometric light curve of SN 2020esmrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintPhase[-12/307] Phase, days (1)dtime.phasefloatLum[0.0019/2.6] Luminosity, 10^+43^erg/s1e+36Wphys.luminosityfloate_Lum[0.0003/0.4] Uncertainty in Lum1e+36Wstat.errorfloatJ/ApJ/927/78/tablea1Observed photometry of SN 2020esmrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMJD[58932.26/59313.42] Modified Julian Date of Observation (JD-2400000.5)dtime.epochdoublePhase[-11.9/356.02] Phase, Rest-frame Days (1)dtime.phasefloatFiltFilter observedmeta.notecharInstInstrument or facility used (2)meta.id;instrcharomag[16/25] Observed AB magnitude in Filtmagphot.magfloate_omag[0.006/0.4] Uncertainty in omagmagstat.error;phot.magfloatFlux[0.003/27] Flux, 10^-16^erg/s/cm^2^/{AA}1e-16cW.m**-2.nm**-1phot.fluxfloate_Flux[0.0003/1.5] Uncertainty in Flux1e-16cW.m**-2.nm**-1stat.error;phot.fluxfloatJ/ApJ/927/78/tablea2Observing details of the optical spectra of SN 2020esmrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintDateDate of observation (UT)time.epochnullablePhase[-11.8/306.9] Rest-frame days relative to B-band maximum (MJD58944.58)dtime.phasefloatTelTelescope+InstrumentinstrcharSlit[1/2] Slit widtharcsecspect.line.widthfloatGrismGrism/Gratingmeta.notecharExpExposure time(s)stime.duration;obs.exposurecharFileName of the ASCII file in subdirectory "sp"; column added by CDSmeta.id;meta.filecharspInteractive spectrum plotmeta.ref.urlchar