Welcome to the home of BINSTAR

BINSTAR is the detailed binary stellar evolution code developed at the Institut d'Astronomie et d'Astrophysique.

It is based on the highly successful STAREVOL single-star code. It incorporates STAREVOL's physics package, namely a nuclear network containing 185 reactions, OPAL and molecular opacity, the Pols. et al equation of state, convection by mixing length theory, overshooting, semi-convection, thermohaline and rotationally induced mixing, structural deformation due to rotation and tides. This code is mainly designed to study low/intermediate-mass binaries.

The BINSTAR project is currently developed by Lionel Siess, Philip Davis and Romain Deschamps in collaboration with our VUB colleagues. Details about the code can be found in

  • Binary evolution using the theory of osculating orbits: conservative Algol evolution
    Davis P., Siess L., Deschamps R., A&A, 2014, 570, A24 arXiV
  • IP Eri: A surprising long-period binary system hosting a He white dwarf
    Merle T., Jorissen A, Masseron T., Van Eck S., Siess L., Van Winckel H., A&A, 2014, 567, 30 arXiV
  • The formation of long-period eccentric binaries with a helium white dwarf
    Siess L., Davis P., Jorissen A., A&A, 2014, 567, 67 PDF
  • Critically-rotating accretors and non-conservative evolution in Algols
    Deschamps R., Siess L., Davis P., Jorissen A., A&A, 2013, 557, 40 arXiv
  • Mass transfer in eccentric binary systems using the binary evolution code BINSTAR
    Davis P., Siess L., Deschamps R., A&A, 2013, 556, 4 arXiv
  • BINSTAR: a new binary stellar evolution code. Tidal interactions
    Siess L., Izzard R, Davis P., Deschamps R. 2013, A&A, 550, 100 PDF

BINSTAR allows the fully implicit computation of both stars of a binary system and its orbital motion simultaneously. The project started in 2008 with the impulse of the European Union (Marie Curie grant agreement 220440 to R. Izzard)

The main features include:

  • A Henyey solver which calculates both stars and the orbital properties separation (a) and eccentricity (e) simultaneously.
  • Tidal interaction using Hut (1981) and Zahn (1977, 1989) formalisms with self-consistent calculation of the E2 and k2 coefficients.
  • Magnetic braking due to disc locking and enhanced magnetic winds (e.g. Dervisoglu et al. 2010)
  • RLOF mass transfer following the de Ritter (1988) prescription supplemented by Kolb & Ritter (1990)
  • Mass transfer in eccentric binaries with asynchronously rotating stars (Sepinsky 1997)
  • In case of direct impact, the accreted angular momentum is estimated by calculating the ballistic trajectory of a test particle in the gainer's Roche potential (Flannery 1975)
  • Various wind accretion prescription (Bondi-Hoyle, de Meideros, Abate)
  • the physics of the hot spot is also accounted for (Deschamps et al 2013)
  • theory of osculating elements implemented in BINSTAR (Davis et al 2014)
  • deformation of the stellar structures due to spin and/or tides
  • eccentricity generation due to mass transfer and induced by the presence of a circumbinary disc.