J/A+A/556/L1ivo://CDS.VizieR/J/A+A/556/L1doi:10.26093/cds/vizier.35569001CDSVlemmings W.H.T.Maercker M.Lindqvist M.Mohamed S.Olofsson H.,Ramstedt S.Brunner M.Groenewegen M.A.T.Kerschbaum F.Wittkowski M.2014-02-17T13:38:14Z2013-07-24T09:19:19ZCDS support team

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

cds-question@unistra.frgiant-starschemical-abundancesradio-spectroscopyThe detached-shell source R Scl, displaying CO emission from recent mass loss, in a binary-induced spiral structure as well as in a clumpy shell produced during a thermal pulse, provides a unique laboratory for studying the differences in CO isotope abundances throughout its recent evolution. We observed both the ^12^CO(J=3-2) and the ^13^CO(J=3-2) line using ALMA. We find significant variations in the ^12^CO/^13^CO intensity ratios and consequently in the abundance ratios. The average CO isotope abundance ratio is at least a factor three lower in the shell (~19) than that in the present-day (<~300yr) mass loss (>60). Additionally, variations in the ratio of more than an order of magnitude are found in the shell itself. We attribute these variations to the competition between selective dissociation and isotope fractionation in the shell, of which large parts cannot be warmer than ~35K. However, we also find that the ^12^CO/^13^CO ratio in the present-day mass loss is significantly higher than the ^12^C/^13^C ratio determined in the stellar photosphere from molecular tracers (~19). The origin of this discrepancy is still unclear, but we speculate that it is due to an embedded source of UV-radiation that is primarily photo-dissociating ^13^CO. This radiation source could be the hitherto hidden companion. Alternatively, the UV-radiation could originate from an active chromosphere of R Scl itself. Our results indicate that caution should be taken when directly relating the ^12^CO/^13^CO intensity and ^12^C/^13^C abundance ratios for specific asymptotic giant branch stars, in particular binaries or stars that display signs of chromospheric stellar activity.2013A&A...556L...1Vhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/556/L1CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/AJ/143/36 : A catalog of Galactic infrared carbon stars (Chen+, 2012)J/ApJS/190/203 : 3.6 years of DIRBE NIR stellar light curves (Price+, 2010)J/A+A/429/235 : Effective temperatures of 119 C-rich giants (Bergeat+, 2005)J/A+A/390/967 : Carbon-rich giants in the HR diagram (Bergeat+, 2002)J/A+A/374/968 : Photometric & kinematic properties of LPVs (Mennessier+, 2001)J/A+A/285/247 : Molecules in O- and C-rich envelopes (Bujarrabal+ 1994)J/A+AS/102/361 : Li abundances in galactic C-stars (Boffin+ 1993)J/A+AS/99/291 : CO & HCN observations of circumstellar envelopes (Loup+ 1993)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/556/L1https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/556/L1http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/556/L1https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/556/L1https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/556/L1http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/556/L1GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/556/L1/fits (FITS file designation in fits directory)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/556/L1/fits?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/556/L1/fits?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/556/L1/fits?GETtext/xml+votable180.050000true21.7421-32.543220.0055555555555555566/35641https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/556/L1?format=asciiRadiodefaultJ/A+A/556/L1/fitsFITS file designation in fits directoryrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right Ascension of center (J2000)degpos.eq.ra;meta.mainDEJ2000Declination of center (J2000)degpos.eq.dec;meta.mainscale[0.3] Scale of the imagearcsec/pixinstr.scalefloatNx[432] Number of pixels along X-axispixmeta.numberintNy[432] Number of pixels along Y-axispixmeta.numberintNz[25] Number of channelspixmeta.numberintRFreq[330/346] Rest frequencyGHzem.freqfloatFreq1Lower value of the frequencyGHzem.freqfloatFreq2Upper value of the frequencyGHzem.freq;stat.maxfloatdFreqResolution (step) in the frequencyMHzspect.resolutionfloatdatacubeDownload the FITS cubemeta.ref.urlcharFileNameName of FITS file in subdirectory fitsmeta.id;meta.fitscharLineTitle of the FITS cubemeta.id;spect.line