Invited review abstract
Binary star formation
Abstract
During the 1990s, binary star formation became one of the critical litmus tests of
star formation theory, a development driven both by the availability of systematic
binarity surveys and the advent of codes with the capability of following collapse to
stellar densities. To some extent, this effort has slowed due in part to an observational concentration on the search for planetary mass companions together with the push, on the theory side, towards cluster scale simulations.
Eduardo Delgado, who died tragically in 2007, was one of the researchers who most thoroughly explored the consequences of the hydrodynamic codes available at the time for the statistical properties of binary stars. Although a theorist, he recognised that observational data provides the most exacting calibrator of theoretical models and was always scrupulous in comparing model outputs with observations. In this review, I take a look at how the field has moved on since Eduardo's death: for example, some of the results he obtained (regarding the predicted plethora of low mass companions at large radii) were almost certainly an artefact of the isothermal equation of state employed at the time. Indeed, the notable development since Eduardo's time has been the pursuit, by a number of groups, of simulations that include additional physics such as magnetic fields, radiative transfer and
mechanical and thermal feedback. These simulations are just beginning to be brought to bear on the binary star formation problem. I shall argue that the subject is ripe for re-investigation, both theoretical and observational, and emphasise that one of the most
basic theoretical problems (which Eduardo was working on at the time of his death: namely the common existence in nature of binaries of highly unequal mass) remains unsolved today.
star formation theory, a development driven both by the availability of systematic
binarity surveys and the advent of codes with the capability of following collapse to
stellar densities. To some extent, this effort has slowed due in part to an observational concentration on the search for planetary mass companions together with the push, on the theory side, towards cluster scale simulations.
Eduardo Delgado, who died tragically in 2007, was one of the researchers who most thoroughly explored the consequences of the hydrodynamic codes available at the time for the statistical properties of binary stars. Although a theorist, he recognised that observational data provides the most exacting calibrator of theoretical models and was always scrupulous in comparing model outputs with observations. In this review, I take a look at how the field has moved on since Eduardo's death: for example, some of the results he obtained (regarding the predicted plethora of low mass companions at large radii) were almost certainly an artefact of the isothermal equation of state employed at the time. Indeed, the notable development since Eduardo's time has been the pursuit, by a number of groups, of simulations that include additional physics such as magnetic fields, radiative transfer and
mechanical and thermal feedback. These simulations are just beginning to be brought to bear on the binary star formation problem. I shall argue that the subject is ripe for re-investigation, both theoretical and observational, and emphasise that one of the most
basic theoretical problems (which Eduardo was working on at the time of his death: namely the common existence in nature of binaries of highly unequal mass) remains unsolved today.