J/A+A/665/A82ivo://CDS.VizieR/J/A+A/665/A82doi:10.26093/cds/vizier.36650082CDSOlofsson H.Khouri T.Sargent B.A.Winnberg A.Blommaert J.A.D.L.,Groenewegen M.A.T.Muller S.Kastner J.H.Meixner M.Otsuka M.,Patel N.Ryde N.Srinivasan S.2022-10-19T14:24:57Z2022-09-15T08:15:25ZCDS support team

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

cds-question@unistra.frgiant-starsinfrared-sourcesradio-astronomyco-line-emissionOH/IR stars are examples of late stellar evolution on the asymptotic giant branch (AGB), and they are, as such, important objects to study. They are also excellent probes of stellar populations, in particular in regions of high interstellar extinction such as the central regions of our Galaxy. Our goal is to characterise the stellar and circumstellar properties of high-mass-loss-rate OH/IR stars in the inner Galactic Bulge using the Atacama Large Millimeter/submillimeter Interferometer (ALMA). Rotational lines of ^12^CO and ^13^CO, as well as a millimetre-wave continuum, have been observed for a sample of 22 OH/IR stars in directions within 2{deg} of the Galactic Centre. Photometry data (~1-30um) have been gathered from the literature to construct spectral energy distributions (SEDs) and to determine pulsational variability. Radiative transfer models have been used to interpret the line and photometry data. All stars in the sample were detected in at least one CO line, and eight objects were detected in 324GHz continuum. Based on luminosity criteria, the sample is divided into 17 objects that most likely lie within the inner Galactic Bulge, and five objects that are most likely foreground objects. The median luminosity of the inner-Galactic-Bulge sub-sample, 5600L_{sun}_, corresponds to an initial mass in the range 1.2-1.6M_{sun}_, indicating that these inner-Galactic-Bulge OH/IR stars descend from solar-type stars. The objects in this sub-sample are further divided into two classes based on their SED characteristics: Eleven objects have SEDs that are well matched by models invoking dust envelopes extending from a few stellar radii and outwards, while six objects are better modelled as having detached dust envelopes with inner radii in the range 200-600au and warmer central stars. The former objects have periodic variability, while the latter objects are predominantly non-periodic. The median gas-mass-loss rate, gas terminal expansion velocity, gas-to-dust mass ratio, and circumstellar ^12^CO/^13^CO abundance ratio have been estimated to be 2x10^-5^M_{sun}_/yr, 18km/s, 200 (excluding the sources with detached dust envelopes, which show markedly lower gas-to-dust ratios), and 5, respectively, for the inner-Galactic-Bulge sub-sample. All line brightness distributions are resolved at an angular scale of ~0.15", but only two objects show a structure in their circumstellar envelopes at our resolution and sensitivity. In both cases, this structure takes the form of a cavity and a bipolar morphology. The inner-Galactic-Bulge sub-sample consists of high mass-loss-rate stars that descend from solar-type progenitors and that lie near the tip of the AGB. Some of the sample stars may have recently ceased mass loss and, hence, have begun to evolve beyond the AGB, as evidenced by a change in circumstellar characteristics and indications of warmer central stars. The inferred very low stellar ^12^C/^13^C isotope ratios are indicative of CNO-cycle nuclear processing, and they are most likely established at the surfaces of the stars during the first dredge-up on the red giant branch since these stars are not expected to experience hot-bottom burning. The inner-Galactic-Bulge OH/IR stars studied here constitute an excellent sample of equidistant objects for the purpose of understanding the evolution of the mass-loss-rate characteristics at the tip of the AGB.2022A&A...665A..82Ohttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/665/A82CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/665/A82https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/665/A82http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/665/A82https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/665/A82https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/665/A82http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/665/A82GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/665/A82/sources (List of sources)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/665/A82/sources?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/665/A82/sources?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/665/A82/sources?GETtext/xml+votable180.050000true265.11037-30.494150.005555555555555556Cone search capability for table J/A+A/665/A82/list (List of fits images and datacubes)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/665/A82/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/665/A82/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/665/A82/list?GETtext/xml+votable180.050000true265.11037-30.494150.005555555555555556Associated datahttps://cdsarc.cds.unistra.fr/assocdata/?obs_collection=J/A+A/665/A825/7207 6/28822 28826-28827 28848-28849 28853https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/665/A82?format=asciiInfraredRadiodefaultJ/A+A/665/A82/sourcesList of sourcesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintID[a-v] Identification lettermeta.idcharNameSource Namemeta.id;meta.maincharRAJ2000Right Ascension of center (J2000)degpos.eq.ra;meta.mainDEJ2000Declination of center (J2000)degpos.eq.dec;meta.mainPhotDisplay photometric datameta.ref.urlcharFitsList the fits images and datacubesmeta.ref.urlcharJ/A+A/665/A82/photomPhotometry data used to construct the spectral energy distributions for 22 sourcesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintID[a-v] Identification lettermeta.idcharNameSource Namemeta.id;meta.maincharu_lambda[#]meta.code.errorcharComCommentsmeta.notecharlambdaEffective centre wavelength of the photometryumem.wl.effectivedoubleSFlux densityJyphot.flux.density;em.radiodoublee_S? Uncertainty of the flux density estimate (1)Jystat.errordoublenullableScorr? Extinction-corrected flux density (2)Jyphot.flux.density;em.radiofloatnullableInst/CatInstrument/Catalogue from which the data were taken (3)meta.id;meta.datasetcharJ/A+A/665/A82/listList of fits images and datacubesrecnoRecord 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.numberintNyNumber of pixels along Y-axismeta.numberintNz? Number of slice for the datacubemeta.numberintnullableObs.dateObservation datestime.epoch;obsnullablebFreqFrequency or lower value of frequency intervalGHzem.freqfloatBFreq? Upper value of frequency intervalGHzem.freq;stat.maxfloatnullabledFreq? Frequency resolutionMHzem.freqdoublenullablesizeSize of FITS fileKibytephys.size;meta.fitsintFileNameName of FITS file, in subdirectory fitsmeta.id;meta.fitscharTitleTitle of the FITS filemeta.title;meta.fitschar