J/A+A/712/A30ivo://CDS.VizieR/J/A+A/712/A30CDSJadlovsky D.Molnar L.Ercolino A.Bernini-Peron M.Merand A.,Krticka J.Wang L.Adam R.Z.Baade D.Bayo A.Gonzalez-Tora G.,Granzer T.Henry G/W/Janik J.Kolar J.Kravchenko K.Langer N.,Oskinova L.M.Pauli D.Ramachandran V.Rubio A.C.Sander A.A.C.,Strassmeier K.G.Weber M.Wittkowski M.Brahm R.Schaffenroth V.,Vanzi L.Skarka M.2026-08-03T08:46:01Z2026-08-03T09:39:19ZCDS support team

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

cds-question@unistra.freclipsing-binary-starsradial-velocityvisible-astronomyThe majority of massive stars are part of binary systems and may interact with their companions during their evolution. This has important consequences for systems in which one star evolves into a red supergiant (RSG). However, not many RSGs have been found in binary systems, and only a few have constrained orbital parameters. We aim to better characterize and constrain the properties of some of the known RSGs in binaries. We were inspired to do so by recent observations where these RSGs transitioned to an earlier spectral type, likely following a major interaction event with their companions. We searched the available TESS photometry for eclipsing companions. We focused on the best candidate, the VV Cephei-type RSG binary KQ Pup, which is made up of an RSG, KQ Pup A, and a B-type companion, KQ Pup B and has an orbital period of 26 years. For this system, we have enough data to constrain the system properties. We used archival photometry and UV spectroscopy along with newly acquired optical spectra and interferometric data from VLTI-GRAVITY. Using TESS light curves, we discovered eclipses with a period of 17.2596d associated with KQ Pup B, making it a binary. We refer to the two components as KQ Pup Ba and Bb. Meanwhile, the detection of the hydrogen Br{gamma} line with VLTI-GRAVITY enabled us to track the orbital motion of the Ba+Bb pair relative to A and thus determine the astrometric orbit of A+B. The dynamical masses agree with independent estimates from asteroseismology and evolutionary models. The results give a mass of ~10M_{sun}_ for the RSG KQ Pup A and ~14M_{sun}_ for the sum of the hot components Ba+Bb. The observed properties of the system are compatible with a coeval hierarchical triple star, where we constrained the mass of KQ Pup Bb to be >~1.2M_{sun}_. We determined an orbital parallax of {pi}=1.24^+0.05^_-0.04_mas based on the detailed orbital model of the system, which is the first such parallax measurement for an RSG, and the value is consistent with Gaia DR3. KQ Pup represents a unique demonstration of mass transfer in a wide, eccentric RSG system. The variability of Balmer emission lines and the detection of Br{gamma} are a strong signature of accretion to the Ba+Bb pair near periastron. With the RSG filling its Roche lobe by only ~70% at periastron ({phi}_A+B_~0), the mass transfer is instead driven by accretion from its extended atmosphere via the wind Roche-lobe overflow. The accretion disk is formed already by {phi}_A+B_~0.95, while TESS light curves also begin to show a signature of occultations by the circumbinary disk, similar to young stellar objects. Through apastron ({phi}_A+B_~0.5), Balmer emissions weaken and indicate a decaying disk. Overall, using TESS, we discovered that several previously assumed RSG binaries host eclipsing inner systems, corresponding to ~10% of all known Galactic RSG binaries. This suggests that many of the other RSG binaries may also be hierarchical triples.2026A&A...712A..30Jhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/712/A30CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/A+A/258/423 : Spectrum of KQ Pup (Muratorio+ 1992)J/A+AS/92/685 : Optical and UV Spectrum of KQ Pup (Altamore+ 1992)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/712/A30https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/712/A30http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/712/A30https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/712/A30https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/712/A30http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/712/A30GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/A+A/712/A30/tablea4KQ Pup system radial velocitiesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintInstInstrument/source namemeta.id;meta.maincharMJDModified Julian date (MJD=HJD-2400000.5)dtime.epochdoubleRVA? Radial velocity for Akm/sphys.veloc;pos.heliocentricfloatnullablee_RVA? Error on radial velocity for Akm/sstat.errorfloatnullableRVB? Radial velocity for Bkm/sphys.veloc;pos.heliocentricfloatnullablee_RVB? Error on radial velocity for Bkm/sstat.errorfloatnullable