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dc.contributor.authorRizzo, JR
dc.contributor.authorGómez, JF
dc.contributor.authorMiranda, LF
dc.contributor.authorOsorio, M
dc.contributor.authorSuárez, O
dc.contributor.authorDurán-Rojas, MC
dc.date.accessioned2019-02-04T16:23:00Z
dc.date.issued2013-12-09
dc.description.abstractContext. Water fountain stars represent a stage between the asymptotic giant branch (AGB) and planetary nebulae phases, when the mass loss changes from spherical to bipolar. These types of evolved objects are characterized by high-velocity jets in the 22 GHz water maser emission. Aims. The objective of this work is to detect and study in detail the circumstellar gas in which the bipolar outflows are emerging. The detection and study of thermal lines may help in understanding the nature and physics of the envelopes in which the jets are developing. Methods. We surveyed the CO and 13CO line emission towards a sample of ten water fountain stars through observing the J = 1 → 0 and 2 → 1 lines of CO and 13CO, using the 30 m IRAM radio-telescope at Pico Veleta. All the water fountains visible from the observatory were surveyed. Results. Most of the line emission arises from foreground or background Galactic clouds, and we had to thoroughly analyse the spectra to unveil the velocity components related to the stars. In two sources, IRAS 18460-0151 and IRAS 18596+0315, we identified wide velocity components with a width of 35 - 40 km s-1 that are centred at the stellar velocities. These wide components can be associated with the former AGB envelope of the progenitor star. A third case, IRAS 18286-0959, is reported as tentative; in this case a pair of narrow velocity components, symmetrically located with respect to the stellar velocity, have been discovered. We also modelled the line emission using an LVG code and derived some global physical parameters, which allowed us to discuss the possible origin of this gas in relation to the known bipolar outflows. For IRAS 18460-0151 and IRAS 18596+0315, we derived molecular masses close to 0.2 M⊙, mean densities of 104 cm-3, and mass-loss rates of 10 -4 M⊙ yr-1. The kinetic temperatures are rather low, between 10 and 50 K in both cases, which suggests that the CO emission is arising from the outer and cooler regions of the envelopes. No fitting was possible for IRAS 18286-0959, because line contamination can not be discarded in this case. Conclusions. The molecular masses, mean densities, and mass-loss rates estimated for the circumstellar material associated with IRAS 18460-0151 and IRAS 18596+0315 confirm that these sources are at the end of the AGB or the beginning of the post-AGB evolutionary stages. The computed mass-loss rates are among the highest ones possible according to current evolutionary models, which leads us to propose that the progenitors of these water fountains had masses in the range from 4 to 8 M ⊙. We speculate that CO emission is detected in water fountains as a result of a CO abundance enhancement caused by current episodes of low-collimation mass-loss. © ESO, 2013.en_GB
dc.description.sponsorshipMICINNen_GB
dc.description.sponsorshipJunta de Andalucíaen_GB
dc.identifier.citationVol. 560, article A82en_GB
dc.identifier.doi10.1051/0004-6361/201322187
dc.identifier.grantnumberCSD2009-00038en_GB
dc.identifier.grantnumberAYA2009-07304en_GB
dc.identifier.grantnumberAYA2012-32032en_GB
dc.identifier.grantnumberAYA2008-06189-C03-01en_GB
dc.identifier.grantnumberAYA2011-30228-C03-01en_GB
dc.identifier.urihttp://hdl.handle.net/10871/35721
dc.language.isoenen_GB
dc.publisherEDP Sciences for European Southern Observatory (ESO)en_GB
dc.subjectmasersen_GB
dc.subjectstars: AGB and post-AGBen_GB
dc.subjectstars: evolutionen_GB
dc.subjectstars: winds, outflowsen_GB
dc.subjectISM: moleculesen_GB
dc.titleSensitive CO and 13CO survey of water fountain stars Detections towards IRAS 18460-0151 and IRAS 18596+0315en_GB
dc.typeArticleen_GB
dc.date.available2019-02-04T16:23:00Z
dc.identifier.issn0004-6361
dc.description This is the author accepted manuscript. The final version is available from EDP Sciences via the DOI in this recorden_GB
dc.identifier.journalAstronomy and Astrophysicsen_GB
dc.rights.urihttp://www.rioxx.net/licenses/all-rights-reserveden_GB
dcterms.dateAccepted2013-09-28
rioxxterms.versionAMen_GB
rioxxterms.licenseref.startdate2013-12-09
rioxxterms.typeJournal Article/Reviewen_GB
refterms.dateFCD2019-02-04T16:19:30Z
refterms.versionFCDAM
refterms.dateFOA2019-02-04T16:23:03Z
refterms.panelBen_GB


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