J/A+A/709/L13ivo://CDS.VizieR/J/A+A/709/L13CDSPardo J.R.Cernicharo J.Fonfria J.P.Cabezas C.Agundez M.Tercero B.,Marcelino N.de Vicente P.Velilla-Prieto L.Guelin M.2026-05-19T14:14:26Z2026-05-12T08:49:34ZCDS support team

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

cds-question@unistra.frvariable-starsspectroscopyThe sub-milliKelvin sensitivity achieved in the Q-band (31-50GHz) line survey of IRC+10216 obtained with the Yebes 40m telescope reveals the presence of several new vibrational HC_9_N overtones (nu_19_>=2) beyond the already reported nu_19_=1. The newly found series of rotational lines appears in seven groups with rotational constants (B) between 291.252 and 293.465MHz, with integer quantum numbers from J_up_=54 to 81 and upper-level excitation energies up to ~600K, well above what is typical of lines found in the outer part of this circumstellar envelope. All evidence, especially the spectral splitting of the l-doubling components and the spacing between B values, unambiguously points toward rotational lines within nu_19_=2-8 that appear surprisingly strong, possibly due to very efficient infrared pumping and slow decay via the nu_19_ mode. The detection of nu_19_=5, 6, 7, and 8 has been possible thanks to collapsed l-doubling components to a single or only two spectral features per rotational transition. To obtain a correct determination of the abundance of HC_9_N in IRC+10216 one has to take into account that about ~70% is estimated to be in the vibrationally excited nu_19_ states.2026A&A...709L..13Phttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/709/L13CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/A+A/330/676 : IRC+10216 Silicon and sulfur chemistry (Willacy+ 1998)J/ApJ/688/L83 : Detection of C_5_N^-^ in IRC +10216 (Cernicharo+, 2008)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/A+A/574/A56 : IRC +10216 17.8GHz-26.3GHz spectrum (Gong+, 2015)J/ApJ/806/L3 : Disilicon carbide (SiCSi) discovery in CW LeoJ/A+A/601/A4 : IRC+10216 carbon chains mapped with ALMA (Agundez+, 2017)J/A+A/606/A74 : IRC +10216 13.3GHz-18.5GHz spectrum (Zhang+, 2017)J/A+A/618/A4 : IRC+10216 as a spectroscopic laboratory (Cernicharo+, 2018)J/A+A/629/A146 : ALMA data cubes for IRC+10216 (Velilla-Prieto+, 2019)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)J/A+A/675/A139 : CI 609um and CII 158um spectra of IRC +10216 (Jeste+, 2023)J/A+A/706/A127 : CIT 6 and IRC+10216 30-50GHz spectra (Nguyen-Luong+, 2026)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/709/L13https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/709/L13http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/709/L13https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/709/L13https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/709/L13http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/709/L13GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapdefaultJ/A+A/709/L13/tablea1Complete list of HC_9_N lines identified in this workrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTransHC_9_N Transitionphys.atmol.transProb;phys.atmol.transitioncharnuObsObserved frequencyMHzem.freqdoubleSulQuantum-mechanichal line strengthspect.line.intensityfloatn_Sul(x 4)meta.notecharEupUpper energy levelKphys.energy;phys.atmol.levelfloatWIntegrated intensity, W={int}T_MB_dvmK.km/sspect.line.intensityfloatn_W[*] Note on W (2)meta.notecharRotDiagRotation diagram (1)phys.atmolfloat