SIMBAD references

We consider the formation and migration of protoplanetary embryos in discs around the stars in tight binary systems (separations of ∼20au). In such systems, the initial stages of runaway embryo formation are expected to only take place within some critical disc radius a_crit, due to the perturbing effect of the binary companions. We perform N-body simulations of the evolution of such a population of inner-disc embryos surrounded by an outer disc of smaller planetesimals. Taking Alpha Centauri-B as our fiducial reference example in which a_crit∼ 0.7au, and using a Minimum Mass Nebular Model with Σ ∝ a^–3/2, we find that within 10⁶yr (10⁷yr), systems will on average contain embryos which have migrated out to 0.9au (1.2au), with the average outermost body having a mass of 0.2M_⊕(0.4M_⊕). Changes to increase the surface density of solids or to use a flatter profile both produce increased embryo migration and growth. At a given time, the relative change in the semimajor axis of the outermost embryo in these simulations is found to be essentially independent of a_crit, and we note that little further embryo migration takes place beyond 10⁷yr. We conclude that the suppression of runaway growth outside a_crit does not mean that the habitable zones in such tight binary systems will be devoid of detectable, terrestrial mass planets, even if a_crit lies significantly interior to the inner edge of the habitable zone.