Discovery of a 0.64 M ⊙ 13.4 au Companion to the roAp Star HIP 47145 = HR 3831 = IM Vel

Our knowledge about the multiplicity of intermediate mass A- and B-type stars is still incomplete, in particular for high (3+) multiplicity systems. Here we report the discovery of a new companion to the nearby roAp star HIP 47145 = HR 3831 with a K band flux ratio of 4% based on a VLTI/GRAVITY interferometric observation. This new 0.64M ⊙ companion at a projected separation 187.5 mas ↔ 13.40 au explains the Hipparcos-GaiaDR2 proper motion change of HR 3831. Together with the previously known M ≈ 1M ⊙ companion at 3″ ↔ 214 au, this makes HR 3831 a hierarchical triple and a very likely progenitor for a system similar to 40 Eridani.

[1]  B. Katz,et al.  Binarity and beyond in A stars – I. Survey description and first results of VLTI/GRAVITY observations of VAST targets with high Gaia-Hipparcos accelerations , 2022, Monthly Notices of the Royal Astronomical Society.

[2]  R. Kotak,et al.  Gaia Early Data Release 3 , 2021, Astronomy & Astrophysics.

[3]  Timothy D. Brandt.  The Hipparcos–Gaia Catalog of Accelerations , 2018, The Astrophysical Journal Supplement Series.

[4]  C. Neiner,et al.  A volume-limited survey of mCP stars within 100 pc – I. Fundamental parameters and chemical abundances , 2018, Monthly Notices of the Royal Astronomical Society.

[5]  et al,et al.  Gaia Data Release 2 , 2018, Astronomy & Astrophysics.

[6]  S. Rabien,et al.  First light for GRAVITY: Phase referencing optical interferometry for the Very Large Telescope Interferometer , 2017, 1705.02345.

[7]  Aaron Dotter,et al.  MESA ISOCHRONES AND STELLAR TRACKS (MIST) 0: METHODS FOR THE CONSTRUCTION OF STELLAR ISOCHRONES , 2016, 1601.05144.

[8]  Dean M. Townsley,et al.  MODULES FOR EXPERIMENTS IN STELLAR ASTROPHYSICS (MESA): BINARIES, PULSATIONS, AND EXPLOSIONS , 2015, 1506.03146.

[9]  A. Amorim,et al.  GRAVITY data reduction software , 2014, Astronomical Telescopes and Instrumentation.

[10]  Harvard-Smithsonian CfA,et al.  Stellar Multiplicity , 2013, 1303.3028.

[11]  M. H. Montgomery,et al.  MODULES FOR EXPERIMENTS IN STELLAR ASTROPHYSICS (MESA): PLANETS, OSCILLATIONS, ROTATION, AND MASSIVE STARS , 2013, 1301.0319.

[12]  Frank Timmes,et al.  MODULES FOR EXPERIMENTS IN STELLAR ASTROPHYSICS (MESA) , 2010, 1009.1622.

[13]  Nikolai Piskunov,et al.  Multi-element abundance Doppler imaging of the rapidly oscillating Ap star HR 3831 , 2004 .

[14]  C. Corbally.  Close visual binaries.I.MK classifications. , 1984 .

[15]  D. Kurtz.  Rapidly Oscillating Ap Stars , 1982 .