J/ApJ/747/102ivo://CDS.VizieR/J/ApJ/747/102doi:10.26093/cds/vizier.17470102CDSHema B.P.Pandey G.Lambert D.L.2017-06-20T13:16:16Z2013-10-28T07:57:10ZCDS support team

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

cds-question@unistra.frchemical-abundancesatomic-physicspeculiar-variable-starsObserved spectra of R Coronae Borealis (RCB) and hydrogen-deficient carbon (HdC) stars are analyzed by synthesizing the C_2_ Swan bands (1, 0), (0, 0), and (0, 1) using our detailed line list and the Uppsala model atmospheres. The (0, 1) and (0, 0) C_2_ bands are used to derive the ^12^C abundance, and the (1, 0) ^12^C^13^C band to determine the ^12^C/^13^C ratios. The carbon abundance derived from the C_2_ Swan bands is about the same for the adopted models constructed with different carbon abundances over the range 8.5 (C/He=0.1%) to 10.5 (C/He=10%). Carbon abundances derived from C I lines are about a factor of four lower than the carbon abundance of the adopted model atmosphere over the same C/He interval, as reported by Asplund et al., who dubbed the mismatch between adopted and derived C abundance as the "carbon problem." In principle, the carbon abundances obtained from C_2_ Swan bands and that assumed for the model atmosphere can be equated for a particular choice of C/He that varies from star to star. Then, the carbon problem for C_2_ bands is eliminated. However, such C/He ratios are in general less than those of the extreme helium stars, the seemingly natural relatives to the RCB and HdC stars. A more likely solution to the C_2_ carbon problem may lie in a modification of the model atmosphere's temperature structure. The derived carbon abundances and the ^12^C/^13^C ratios are discussed in light of the double degenerate and the final flash scenarios.2012ApJ...747..102Hhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/747/102CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJS/169/472 : Swan system of C2 (Tanabashi+, 2007)J/AJ/134/1877 : Spectropolarimetry of R CrB in 1998-2003 (Kawabata+, 2007)J/A+A/353/287 : The R CrB stars (Asplund+, 2000)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/747/102https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/747/102http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/747/102https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/747/102https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/747/102http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/747/102GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/747/102/stars (R Coronae Borealis and hydrogen-deficient carbon stars parameters)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/747/102/stars?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/747/102/stars?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/747/102/stars?GETtext/xml+votable180.050000true273.34825-25.7780.0055555555555555566/1954 8701 14626 24147 28774 28881 28970 29214 29841 30208 38333 43378 44328 47661 47814 47869 48038 48507https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/747/102?format=asciidefaultJ/ApJ/747/102/starsR Coronae Borealis and hydrogen-deficient carbon stars parametersrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintStarStar namemeta.id;meta.maincharDateDate of observationtime.epochnullableODateOther date(s) of observationtime.epochcharVmag[6/12.8] Visual validated magnitude (AAVSO)magphot.mag;em.opt.VfloatObsObservatorymeta.id;instr.obstycharS/N[25/250] Signal to noise ratio per pixel of the spectrum in the continuum near the 4737{AA} ^12^C_2_ bandheadstat.snr;instr.pixelintA00Simbad column added by the CDSmeta.ref.urlintnullableSimbadSimbad column added by the CDSmeta.refcharlogE1[5/7] log{epsilon}(Fe) from the 4700{AA} regionarith.zpfloate_logE1[0.1/0.3] Standard deviationstat.errorfloatN1[3/10] Number of lines usedmeta.numberintlogE2? log{epsilon}(Fe) from literature (1)arith.zpfloatnullablel_logE3Limit flag on logE3meta.code.errorcharlogE3log{epsilon}(Fe) from the 4744.4{AA} line, assuming it to be entirely FeIarith.zpfloatTeff[5400/7000] Effective temperatureKphys.temperature.effectiveintnullableloggSurface gravitylog(cm.s**-2)phys.gravityfloatnullableVt[4/8] Turbulence velocitykm/sphys.veloc.microTurbfloatnullablel_Rat1Limit flag on Rat1meta.code.errorcharRat1[3/400] ^12^C/^13^C ratio lower value (or limit) from this workspect.line.intensity;arith.ratiointnullableRat1u? ^12^C/^13^C ratio upper valuespect.line.intensity;arith.ratiointnullablel_Rat2Limit flag on Rat2meta.code.errorcharRat2? ^12^C/^13^C ratio lower value (or limit)spect.line.intensity;arith.ratiointnullableRat2u? ^12^C/^13^C ratio upper valuespect.line.intensity;arith.ratiointnullabler_Rat2[bcde,] Reference(s) for Rat2 (2)meta.ref;pos.framechar_RAPositions from SIMBAD database (right ascension part)degpos.eq.ra;meta.main_DEPositions from SIMBAD database (declination part)degpos.eq.dec;meta.mainJ/ApJ/747/102/table2Sample lines for (1, 0) C2 Swan bandrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBandBand identification ((0,0), (0,1) or (1,0))meta.code;instr.bandpasscharC2The C_2_ identification (^12^C^13^C or ^12^C_2_)phys.atmol.ionStagelambda[4692.34/5635.5] Wavelength {lambda} in {AA}0.1nmem.wldoubleJ"[5/62] J value of lower levelphys.atmol.qnfloatchi[0.19/0.94] Lower excitation potentialeVphys.atmol.excitation;stat.minfloatlog(gf)[-0.985/0.474] Log of the oscillator strengthphys.atmol.oscStrengthfloat