J/A+A/629/A94ivo://CDS.VizieR/J/A+A/629/A94doi:10.26093/cds/vizier.36290094CDSDiaz-Luis J.J.Alcolea J.Bujarrabal V.Santander-Garcia M.,Castro-Carrizo A.Gomez-Garrido M.Desmurs J.-F.2019-11-27T14:16:40Z2019-09-12T09:00:38ZCDS support team

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

cds-question@unistra.frvariable-starsco-line-emissionradio-spectroscopyWe aim to study the main properties of a volume-limited unbiased sample of well characterized semi-regular variables (SRs) in order to clarify important issues that need to be further explained, such as the formation of axially symmetric planetary nebulae (PNe) from spherical circumstellar envelopes (CSEs) that takes place during the mass loss process along the AGB phase. We present new high S/N IRAM 30m observations of the ^12^CO J=2-1, ^12^CO J=1-0, and ^13^CO J=1-0 lines, in a volume-limited sample of SRs for which the Hipparcos distances are between 100-500 pc and declinations above -25{deg}. We analyzed the data by characterizing the main properties of the CSEs. The ^12^CO J=2-1 data have been used to study the profiles, while the ^12^CO J=1-0 data have been used to estimate mass-loss rates for the complete sample. Moreover, the ^12^CO J=2-1 line has been used to determine the possible structures responsible for such profiles. We have classified the sources into four groups according to the different profiles and final gas expansion velocities. Type 1 and 2 profiles are broad and narrow symmetric lines, respectively. Type 1 profiles, furthermore, are more related to standard spherically symmetric envelopes already studied. Type 3 profiles, on the contrary, are strange profiles with very pronounced asymmetries. Type 4 profiles, finally, are those which show two different components: a narrow line profile superimposed on a broad pedestal component. We find that for sources which show this kind of profile, with two different components, the variation amplitude is very low, what means that these SRs do not have a well developed inner envelope differentiated from the outer one. Interestingly, we report a moderate correlation between mass-loss rates and ^12^CO J=1-0/^12^CO J=2-1 line intensity ratios for O-rich SRs, suggesting a different behaviour between C- and O-rich SRs. By using SHAPE+shapemol, we find a unified simple model based on an oblate spheroid, placed in different orientations, that may explain all the ^12^CO profiles in the sample, indicating that the gas expansion is, in general, predominantly equatorial. Moreover, in order to explain the type 4 profiles, we define an extra component which may somehow be a biconical structure or similar according to the structures already found in this kind of sources. Type 1 and 2 profiles, curiously, may also be explained by standard spherically symmetric envelopes, but often requiring anomalously low velocities. Type 3 and 4 profiles, however, need axial symmetry to be explained. We conclude that most circumstellar shells around SRs show axial, strongly non-spherical symmetry. More interferometric observations are needed in order to make firm conclusions about mass-loss processes and possible morphologies of SRs.2019A&A...629A..94Dhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/629/A94CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/629/A94https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/629/A94http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/629/A94https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/629/A94https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/629/A94http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/629/A94GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/629/A94/table1 (Main properties of the observed SRs)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/629/A94/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/629/A94/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/629/A94/table1?GETtext/xml+votable180.050000true4.97544.709440.0055555555555555566/254 1102 2528 2740 2937 3951 4290 4347 6007 6444 8492 8926 9137 9813 9939 9968 10137 10960 11165 11519 12877 12882 13454 13845 14048 14636 15122 15449 16175 18998 20699 21241 21683 21777 22941 23423 24158 25246 26180 26327 26345 29703 30035 30212 32142 32254 36655 40566 487001.6558465556080236e-21 2.1346512726771855e-20https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/629/A94?format=asciiRadiodefaultJ/A+A/629/A94/table1Main properties of the observed SRsStarStar namemeta.id;meta.maincharRAJ2000Simbad right ascension (J2000)pos.eq.ra;meta.mainrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintDEJ2000Declination (J2000)pos.eq.dec;meta.mainVtype[SRa SRb SRc] Variable typemeta.notecharPerPeriod of variabilitydtime.periodintSpType[CMS] Spectral typesrc.spTypecharDVmagVariation amplitude, from GCVS (Samus et al., Cat. B/gcvs)magsrc.var.amplitudefloatF12IRAS 12um fluxJyphot.flux.density;em.IR.8-15umintF25IRAS 25um fluxJyphot.flux.density;em.IR.15-30umintF60IRAS 60um fluxJyphot.flux.density;em.IR.30-60umintF100IRAS 100um fluxJyphot.flux.density;em.IR.60-100umintDistHDistance derived from Hipparcos (van Leeuwen, 2007, Cat. I/311) parallaxpcpos.distance;pos.heliocentricintDistGDistance derived from Gaia DR2 (Gaia Collaboration, 2018, Cat. I/345) parallaxpcpos.distance;pos.heliocentricintsp12_1Show the 12CO(1-0) spectrummeta.ref.urlcharsp12_2Show the 12CO(2-1) spectrummeta.ref.urlcharsp13Show the 13CO(1-0) spectrummeta.ref.urlcharSimbadSimbad column added by the CDSmeta.ref.urlcharJ/A+A/629/A94/spectra*All spectra for the 49 sources of the samplerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintStarStar namemeta.id;meta.maincharLineLine (12CO(1-0), 12CO(2-1) or 13CO(1-0))meta.id;spect.linecharVelVelocitykm/sspect.dopplerVelocdoubleTmbMain-beam brightness temperatureKphys.temperaturedouble