J/A+A/675/A139ivo://CDS.VizieR/J/A+A/675/A139doi:10.26093/cds/vizier.36750139CDSJeste M.Wiesemeyer H.Menten K.M.Wyrowski F.2024-11-28T20:04:05Z2023-07-14T14:02:48ZCDS support team

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

cds-question@unistra.frcarbon-starsspectroscopyThe envelopes of evolved late-type stars on the asymptotic giant branch are characterised by a complex chemistry that is close to thermochemical equilibrium near the stellar surface; however, in the outer envelope, it is dominated by radical reactions, assisted by a photo-chemistry driven by the interstellar radiation field. The study at hand aims to describe the distribution of atomic carbon, C^0^, throughout the envelope, in support of an improved understanding of its photo-chemistry. Additionally, we also briefly discuss the observation of [CII] emission towards the star. We obtain spectra of the [CI] 3P1-3P0 fine structure line (at 492.160700GHz) at projected distances of up to 78 arcsec from the star. The line profiles are characterised by both direct fitting of Gaussian components, and by modelling the observed line of the [CI] triplet. We also report the detection of the 2P3/2-2P1/2 line (at 1900.5369 GHz) from the C^+^ fine structure singlet at the central position and its non-detection at 32 arcsec from the star. The overall picture of the [CI] emission from IRC +10216 agrees with more limited previous studies. The satisfying agreement between the observed and modelled line profiles, with emission at the systemic velocity appearing beyond one beam (13 arcsec HPBW) from the star, rules out that the C^0^ is located in a thin shell. Given that the bond energy of CO falls only 0.1eV below the ionisation threshold of C^0^, the absence of observable [CII] emission from sightlines beyond a projected distance of ~10^17^cm (>~20-30arcsec) from the star (adopting a distance of 130 pc) does not contradict a scenario where the majority of C^0^ is located between that of CO and C^+^, as expected for an external far-ultraviolet radiation field. This conjecture is also corroborated by a model in which the C^0^ shell is located farther outside, failing to reproduce the [CI] line profiles at intermediate sky-plane distances from the star. Comparing a photo-chemical model adopted from literature with the simplifying assumption of a constant C^0^ abundance with respect to the H_2_ density (with the 1/r^2^ fall-off of a mass-conserving expansion flow), we constrain the inner boundary of the [CI] emitting shell, located at ~10^16^cm from the star.2023A&A...675A.139Jhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/675/A139CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/317/503 : Photometric + visibility data of IRC +10 216J/A+A/330/676 : IRC+10216 Silicon and sulfur chemistry (Willacy+ 1998)J/A+AS/142/181 : 2mm molecular line survey of IRC+10 216 (Cernicharo+, 2000)J/ApJS/177/275 : 1.3 and 2mm survey of IRC+10216 (He+, 2008)J/ApJS/190/348 : 1mm spectral survey of IRC+10216 + VY CMa (Tenenbaum+, 2010)J/ApJS/193/17 : Spectral-line survey of IRC+10216 at 293-355GHzJ/A+A/545/A12 : Chemistry of IRC+10216 inner wind modelledJ/ApJ/806/L3 : Disilicon carbide (SiCSi) discovery in CW LeoJ/A+A/574/A56 : IRC +10216 17.8GHz-26.3GHz spectrum (Gong+, 2015)J/A+A/606/A74 : IRC +10216 13.3GHz-18.5GHz spectrum (Zhang+, 2017)J/A+A/601/A4 : IRC+10216 carbon chains mapped with ALMA (Agundez+, 2017)J/A+A/618/A4 : IRC+10216 as a spectroscopic laboratory (Cernicharo+, 2018)J/MNRAS/489/3492 : IRC+10216 + omi Cet SCUBA-2 light curvesJ/A+A/658/A39 : 31.0-50.3 GHz observations of IRC+10216 (Pardo+, 2022)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/675/A139https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/675/A139http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/675/A139https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/675/A139https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/675/A139http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/675/A139GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/675/A139/list (List of fits files)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/675/A139/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/675/A139/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/675/A139/list?GETtext/xml+votable180.050000true146.9892113.278780.0055555555555555566/4365https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/675/A139?format=asciidefaultJ/A+A/675/A139/table1*Input parameters for the RATRAN model of the [CI] emissionrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintDDistance to observerpcpos.distancefloatMdotMass loss ratesolMass/yrphys.mass.lossfloatrinInner radiuscmphys.angSize;srcfloatroutOuter radiuscmphys.angSize;srcfloatnH2(rin)H_2_ number density at inner radiuscm**-3meta.id;meta.mainfloatTrinGas temperature at inner radiusKphys.temperaturefloatvexpExpansion velocitykm/sphys.veloc.expansionfloatDeltav1/e line half-widthkm/sspect.line.widthfloatJ/A+A/675/A139/table2*Parameters deduced from direct fits to the observed spectrarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintoRARight-ascension offset x cos(DE)arcsecpos.eq.ra;arith.difffloatoDEDeclination offsetarcsecpos.eq.dec;arith.difffloatv1LSR velocity at blue-shifted peakkm/sspect.dopplerVeloc;pos.lsrfloate_v1Error on v1km/sstat.errorfloatlineArea1Line area below blue-shifted componentK.km/sphys.area;spect.linefloate_lineArea1Error on lineArea1K.km/sstat.errorfloatDeltav1Width (FWHM) of blue-shifted componentkm/sspect.line.widthfloate_Deltav1Error on delta_v1km/sstat.errorfloatTpeak1Line peak (T_mb_) of blue-shifted peakKphys.temperaturefloatv2LSR velocity at red-shifted peakkm/sspect.dopplerVeloc;pos.lsrfloate_v2Error on v2km/sstat.errorfloatlineArea2Line area below red-shifted componentK.km/sphys.area;spect.linefloate_lineArea2Error on lineArea2K.km/sstat.errorfloatDeltav2Width (FWHM) of red-shifted componentkm/sspect.line.widthfloate_Deltav2Error on delta_v2km/sstat.errorfloatTpeak2Line peak (T_mb_) of red-shifted peakKphys.temperaturefloatJ/A+A/675/A139/listList of fits filesFileNameName of FITS file, in subdirectory fitsmeta.id;meta.fitscharTitleTitle of the FITS filemeta.title;meta.fitscharObs.DateObservation date (YYYY-MM-DDThh:mm:ss)time.epoch;obscharrecnoRecord 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.mainNxNumber of pixels along X-axismeta.numberintbFreqLower value of frequency intervalGHzem.freq;stat.mindoubleBFreqUpper value of frequency intervalGHzem.freq;stat.maxdoubledFreqFrequency resolutionHzspect.resolutiondoublesizeSize of FITS fileKibytephys.size;meta.fitsintJ/A+A/675/A139/listspList of spectrarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSeqLine number within the filemeta.id;meta.mainintIdentIdentifier (1)meta.idcharspShow the spectrummeta.ref.urlcharFileNameName of the fits table with spectra in subdirectory fitsmeta.id;meta.tablecharTitleTitle of the fits filemeta.title;meta.fitschar