Investigating three Sirius-like systems with SPHERE

Astronomy and Astrophysics, vol. 646, pp. A61

Abstract

Context. Sirius-like systems are relatively wide binaries with a separation from a few to hundreds of au; they are composed of a white dwarf (WD) and a companion of a spectral type earlier than M0. Here we consider main sequence (MS) companions, where the WD progenitor evolves in isolation, but its wind during the former asymptotic giant branch (AGB) phase pollutes the companion surface and transfers some angular momentum. They are rich laboratories to constrain stellar models and binary evolution. Aims. Within the SpHere INfrared survey for Exoplanet survey that uses the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument at the Very Large Telescope, our goal is to acquire high contrast multi-epoch observations of three Sirius-like systems, HD 2133, HD 114174, and CD-56 7708 and to combine this data with archive high resolution spectra of the primaries, TESS archive, and literature data. Methods. These WDs are easy targets for SPHERE and were used as spectrophotometric standards. We performed very accurate abundance analyses for the MS stars using methods considered for solar analogs. Whenever possible, WD parameters and orbits were obtained using Monte Carlo Markov chain methods. Results. We found brighter J and K magnitudes for HD 114174B than obtained previously and extended the photometry down to 0.95 μm. Our new data indicate a higher temperature and then shorter cooling age (5.57 ± 0.02 Gyr) and larger mass (0.75 ± 0.03 M⊙) for this WD than previously assumed. Together with the oldest age for the MS star connected to the use of the Gaia DR2 distance, this solved the discrepancy previously found with the age of the MS star. The two other WDs are less massive, indicating progenitors of ∼1.3 M⊙ and 1.5 − 1.8 M⊙ for HD 2133B and CD-56 7708B, respectively. In spite of the rather long periods, we were able to derive useful constraints on the orbit for HD 114174 and CD-56 7708. They are both seen close to edge-on, which is in agreement with the inclination of the MS stars that are obtained coupling the rotational periods, stellar radii, and the projected rotational velocity from spectroscopy. The composition of the MS stars agrees fairly well with expectations from pollution by the AGB progenitors of the WDs: HD 2133A has a small enrichment of n-capture elements, which is as expected for pollution by an AGB star with an initial mass < 1.5 M⊙; CD-56 7708A is a previously unrecognized mild Ba-star, which is also expected due to pollution by an AGB star with an initial mass in the range of 1.5 − 3.0 M⊙; and HD 114174 has a very moderate excess of n-capture elements, which is in agreement with the expectation for a massive AGB star to have an initial mass > 3.0 M⊙. Conclusions. On the other hand, none of these stars show the excesses of C that are expected to go along with those of n-capture elements. This might be related to the fact that these stars are at the edges of the mass range where we expect nucleosynthesis related to thermal pulses. More work, both theoretical and observational, is required to better understand this issue.

Authors 16

1. Anthony Boccaletti

   Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Sorbonne Université · Sorbonne Paris Cité · Laboratoire d’études spatiales et d’instrumentation en astrophysique

   Affiliation as printed

   LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Univ. Paris Diderot, Sorbonne Paris Cité, 5 Place Jules Janssen, 92195 Meudon, France

2. C. Desgrange

   Lyon 1 Université · Centre National de la Recherche Scientifique · Centre de Recherche Astrophysique de Lyon · Universidad Diego Portales

   Affiliation as printed

   CRAL, UMR 5574, CNRS, Université Lyon 1, 9 Avenue Charles André, 69561 Saint Genis Laval Cedex, France

   Núcleo de Astronomía, Facultad de Ingeniería, Universidad Diego Portales, Av. Ejercito 441, Santiago, Chile

3. R. Galicher

   Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Sorbonne Université · Sorbonne Paris Cité · Laboratoire d’études spatiales et d’instrumentation en astrophysique

   Affiliation as printed

   LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Univ. Paris Diderot, Sorbonne Paris Cité, 5 Place Jules Janssen, 92195 Meudon, France

4. C. Ginski Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands

5. J. Hagelberg

   University of Geneva

   Affiliation as printed

   Geneva Observatory, University of Geneva, Chemin des Mailettes 51, 1290 Versoix, Switzerland

6. Silvan Hunziker

   ETH Zurich · Institute for Particle Physics and Astrophysics

   Affiliation as printed

   ETH Zurich, Institute for Particle Physics and Astrophysics, Wolfgang-Pauli-Str. 27, 8093 Zurich, Switzerland

7. A.‐M. Lagrange

   Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Sorbonne Université · Sorbonne Paris Cité · Institut de Planétologie et d'Astrophysique de Grenoble · Laboratoire d’études spatiales et d’instrumentation en astrophysique · Université Grenoble Alpes

   Affiliation as printed

   LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Univ. Paris Diderot, Sorbonne Paris Cité, 5 Place Jules Janssen, 92195 Meudon, France

   Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France

8. C. Lazzoni

   Osservatorio Astronomico di Padova · National Institute for Astrophysics

   Affiliation as printed

   INAF Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy

9. A.-L. Maire

   University of Liège · Max Planck Institute for Astronomy

   Affiliation as printed

   Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany

   STAR Institute, Université de Liège, Allée du Six Août 19c, 4000 Liège, Belgium

10. S. Mazevet

    Université Paris Sciences et Lettres · Observatoire de Paris · Laboratoire Univers et Théories · Université Paris Diderot

    Affiliation as printed

    Laboratoire Univers et Théories, Université Paris Diderot, Observatoire de Paris, PSL University, 5 Place Jules Janssen, 92195 Meudon, France

11. Clément Perrot

    Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Sorbonne Université · Sorbonne Paris Cité · Laboratoire d’études spatiales et d’instrumentation en astrophysique · Millenium Nucleus for Planet Formation · University of Valparaíso

    Affiliation as printed

    Instituto de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Av. Gran Bretaña 1111, Valparaíso, Chile

    LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Univ. Paris Diderot, Sorbonne Paris Cité, 5 Place Jules Janssen, 92195 Meudon, France

    Núcleo Milenio Formación Planetaria – NPF, Universidad de Valparaíso, Av. Gran Bretaña 1111, Valparaíso, Chile

12. Axel Potier

    Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Sorbonne Université · Sorbonne Paris Cité · Laboratoire d’études spatiales et d’instrumentation en astrophysique

    Affiliation as printed

    LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Univ. Paris Diderot, Sorbonne Paris Cité, 5 Place Jules Janssen, 92195 Meudon, France

13. Daniel Rouan

    Centre National de la Recherche Scientifique · Institut de Planétologie et d'Astrophysique de Grenoble · Université Grenoble Alpes

    Affiliation as printed

    Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France

14. Tobias O. B. Schmidt

    Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Sorbonne Université · Sorbonne Paris Cité · Laboratoire d’études spatiales et d’instrumentation en astrophysique

    Affiliation as printed

    LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Univ. Paris Diderot, Sorbonne Paris Cité, 5 Place Jules Janssen, 92195 Meudon, France

15. T. Stolker

    University of Amsterdam

    Affiliation as printed

    Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands

16. A. Vigan

    Centre National de la Recherche Scientifique · Aix-Marseille Université · Laboratoire d’Astrophysique de Marseille

    Affiliation as printed

    Aix-Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France