J/A+A/685/A149ivo://CDS.VizieR/J/A+A/685/A149doi:10.26093/cds/vizier.36850149CDSJensen S.S.Spezzano S.Caselli P.Sipilae O.Redaelli E.Giers K.,Ferrer Asensio J.2024-11-29T20:02:19Z2024-05-17T19:31:04ZCDS support team

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

cds-question@unistra.frmolecular-cloudsinterstellar-mediumspectroscopymillimeter-astronomysubmillimeter-astronomyNitrogen fractionation is a powerful tracer of the chemical evolution during star- and planet formation. This requires robust determinations of the nitrogen fractionation across different evolutionary stages. We aim to determine the ^14^N/^15^N and ^12^C/^13^C ratios for HCN in six starless and prestellar cores and compare the results between the direct method using radiative transfer modeling and the indirect double isotope method assuming a fixed ^12^C/^13^C ratio. We present IRAM observations of the HCN 1-0, HCN 3-2, HC^15^N 1-0 and H^13^CN 1-0 transitions toward six embedded cores. The ^14^N/^15^N ratio is derived using both the indirect double isotope method and directly through non-Local Thermodynamic Equilibrium 1D radiative transfer modeling of the HCN emission. The latter also provides the ^12^C/^13^C ratio, which is compared to the local interstellar value. The derived 14N/15N ratios using the indirect method are generally in the range 300-550 and could suggest an evolutionary trend in the nitrogen fractionation of HCN between starless cores and later stages of the star formation process. However, the direct method reveals lower fractionation ratios of around ~250, mainly resulting from a lower ^12^C/^13^C ratio in the range ~20-40 compared to the local interstellar medium value of 68. This study reveals a significant difference between the nitrogen fractionation ratio in HCN derived using direct and indirect methods. This can influence the interpretation of the chemical evolution and displays the pitfalls of the indirect double isotope method for fractionation studies. However, the direct method is challenging as it requires well- constrained source models to produce accurate results. No trend in the nitrogen fractionation of HCN between earlier and later stages of the star formation process is evident when the results of the direct method are considered.2024A&A...685A.149Jhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/685/A149CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/685/A149https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/685/A149http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/685/A149https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/685/A149https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/685/A149http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/685/A149GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/685/A149/table1 (Observation summary)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/685/A149/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/685/A149/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/685/A149/table1?GETtext/xml+votable180.050000true70.86541729.6530560.0055555555555555566/1050 1114 1126 1159 1168 1290https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/685/A149?format=asciiMillimeterdefaultJ/A+A/685/A149/table1Observation summaryrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSourceSource namemeta.id;meta.maincharRAJ2000Right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainvLSRLSR velocitykm/sphys.veloc;pos.lsrfloatsp1Show the HCN 1-0 spectrummeta.ref.urlcharFileName1Name of HCN 1-0 spectrum file in subdirectory spmeta.id;meta.filecharsp2Show the HCN 3-2 spectrummeta.ref.urlcharFileName2Name of HCN 3-2 spectrum file in subdirectory spmeta.id;meta.filecharsp3Show the H13CN 1-0spectrummeta.ref.urlcharFileName3Name of H13CN 1-0 spectrum file in subdirectory spmeta.id;meta.filecharsp4Show the HC15N 1-0 spectrummeta.ref.urlcharFileName4Name of HC15N 1-0 spectrum file in subdirectory spmeta.id;meta.filechar