J/A+A/713/A283ivo://CDS.VizieR/J/A+A/713/A283CDSMerc J.Jones D.Escorza A.Boffin H.M.J.Reindl N.Abdul-Masih M.,Masseron T.Sowicka P.Kara J.Garcia-Rojas J.Garcia R.A.,Palakkatharappil D.B.Parker Q.A.Zijlstra A.A.Godoy-Rivera D.,Beck P.G.Mathur S.Armas Padilla M.Munoz Darias T.Kucakova H.,Wolf M.Hornoch K.Zasche P.Clavero R.Goodhew P.2026-09-23T07:28:35Z2026-09-23T08:28:08ZCDS support team

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

cds-question@unistra.frinterstellar-mediumplanetary-nebulaespectroscopic-binary-starsmultiple-starslate-type-starsspectroscopyK 1-6 has long been classified as a planetary nebula (PN) hosting a binary central star; however, it has remained poorly studied due to its faintness. The central star exhibits pronounced photometric variability whose origin is still unclear. We present a comprehensive characterisation of the K 1-6 system, including the physical properties of its stellar components and the nature of the surrounding nebulosity. We conducted a multi-wavelength analysis combining optical and UV spectroscopy obtained with the Gran Telescopio Canarias, the Telescopio Nazionale Galileo, the Nordic Optical Telescope, and the Hubble Space Telescope. We also present long-term multi-band ground- and space-based photometry, including high-cadence data from the Transiting Exoplanet Survey Satellite, narrowband imaging, and the latest astrometric constraints from Gaia. Our results show that the nebula is not a remnant PN, but instead consists of interstellar medium photoionised by a hot white dwarf, which is relatively evolved. It has a cooling age of 1-2Myr, implying that any original PN has long since dissipated. We further find that the central object is a hierarchical triple system, comprising an inner binary with an orbital period likely of the order of thousands of days and a distant tertiary companion orbiting on a timescale of tens of thousands of years. The optically dominant cool component of the inner binary is an inflated K-type star displaying extreme magnetic activity, including large-amplitude variability and flaring. Its properties resemble those of BY Dra-type binaries and Abell 35-type systems, and are difficult to reconcile with single-star evolution, pointing instead to a history of binary interaction.2026A&A...713A.283Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/713/A283CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/713/A283https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/713/A283http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/713/A283https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/713/A283https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/713/A283http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/713/A283GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapdefaultJ/A+A/713/A283/listList of spectrarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNxNumber of pixels along X-axismeta.numberintObs.dateObservation datestime.epoch;obsnullableblambdaLower value of wavelength interval0.1nmem.wlfloatBlambdaUpper value of wavelength interval0.1nmem.wlfloatsizeSize of FITS fileKibytephys.size;meta.fitsintspShow the spectrummeta.ref.urlcharFileNameName of FITS file, in subdirectory fitsmeta.id;meta.fitscharTitleTitle of the FITS filemeta.title;meta.fitschar