J/A+A/699/A22ivo://CDS.VizieR/J/A+A/699/A22doi:10.26093/cds/vizier/bc-nv/lccCDSMontarges M.Malfait J.Esseldeurs M.de Koter A.Baron F.Kervella P.,Danilovich T.Richards A.M.S.Sahai R.McDonald I.Khouri T.Shetye S.,Zijlstra A.Van de Sande M.El Mellah I.Herpin F.Siess L.Etoka S.,Gobrecht D.Marinho L.Wallstroem S.H.J.Wong K.T.Yates J.2026-08-03T06:55:36Z2025-06-26T08:28:10ZCDS support team

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

cds-question@unistra.frgiant-starsm-starslate-type-starsgalaxy-classification-systemsvisible-astronomypolarimetryAt the end of their lives, when low- to intermediate-mass stars reach the asymptotic giant branch (AGB), their photosphere expands up to a few hundred times and a strong stellar wind develops. This allows for various types of interactions with celestial bodies in their close circumstellar environment, including mass- and angular-momentum transfer. We aim to characterize the properties of the inner companion of the S-type AGB star pi1 Gru, and to identify plausible future evolution scenarios for this triple system. We observed pi1 Gru with ALMA and VLT/SPHERE. In addition, we collected archival photometry data and used the Hipparcos-Gaia proper motion anomaly. We derive the best orbital parameters from Bayesian inference. The inner companion, pi1 Gru C was located at 37.4+/-2.0mas from the primary in June-July 2019 (projected separation of 6.05+/-0.55au at 161.7+/-11.7pc). The best orbital solution gives a companion mass of 0.86^+0.22^_-0.20_M_{sun}_ (using the derived mass of the primary), and a semi-major axis of 7.05^+0.54^_-0.57_au. This leads to an orbital period of 11.0^+1.7^_-1.5_yr. The best solution is an elliptical orbit with eccentricity e=0.35^+0.18^_-0.17_, but a circular orbit cannot be totally excluded. The close companion can either be a K1V(F9.5V/K7V) star or a white dwarf. The ultraviolet and millimeter continuum photometry are consistent with the presence of an accretion disk around the close companion. The ultraviolet emission could then either originate in hot spots in an overall cooler disk, or also from a hot disk in case the companion is a white dwarf. Though the close companion and the AGB star are interacting, and an accretion disk is observed around the companion, the mass-accretion rate is too low to cause a Ia supernova but could produce nove every ~900yr. Short wavelength spatially resolved observations are needed to further constrain the nature of the C companion. Searches for close-in companions similar to this system will help to better understand the physics of mass- and angular-momentum transfer, and orbital evolution in the late evolutionary stages.2025A&A...699A..22Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/699/A22CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/671/A96 : ATOMIUM - VLT/SPHERE overview (Montarges+, 2023)https://almascience.eso.org/alma-data/lp/atomium : ATOMIUM Home Pagehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/699/A22https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/699/A22http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/699/A22https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/699/A22https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/699/A22http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/699/A22GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/699/A22/list (List of fits images)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/699/A22/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/699/A22/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/699/A22/list?GETtext/xml+votable180.050000true335.6842-45.9480.005555555555555556Associated datahttps://cdsarc.cds.unistra.fr/assocdata/?obs_collection=J/A+A/699/A226/46318https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/699/A22?format=asciiOpticaldefaultJ/A+A/699/A22/listList of fits imagesrecnoRecord 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.mainscaleScale of the imagearcsec/pixinstr.scalefloatNxNumber of pixels along X-axismeta.numberintNyNumber of pixels along Y-axismeta.numberintObs.dateObservation datestime.epoch;obsnullablesizeSize of FITS fileKibytephys.size;meta.fitsintFileNameName of FITS file, in subdirectory fitsmeta.id;meta.fitscharTitleTitle of the filemeta.title;meta.filechar