POSYDON: A General-purpose Population Synthesis Code with Detailed Binary-evolution Simulations (original) (raw)

Rapid binary star evolution for N-body simulations and population synthesis

Monthly Notices of the Royal Astronomical Society, 1997

We present an algorithm for the rapid evolution of binary stars. It is based on simple fitting formulae for the evolution of single stars. Mass loss, mass transfer and common-envelope evolution are followed with the changes to both the mass donor and the accretor where applicable. We describe a procedure for integrating our formulae and give examples of how we can follow the evolution of Algols and cataclysmic variables. The algorithm can be used for simple binary population synthesis. We also explain how we incorporate it into N-body simulations where we introduce a new scheme that deals with colliding stars.

A new, efficient stellar evolution code for calculating complete evolutionary tracks

Monthly Notices of the Royal Astronomical Society, 2009

We present a new stellar evolution code and a set of results, demonstrating its capability at calculating full evolutionary tracks for a wide range of masses and metallicities. The code is fast and efficient, and is capable of following through all evolutionary phases, without interruption or human intervention.

Rapid stellar and binary population synthesis with COMPAS

2021

COMPAS (Compact Object Mergers: Population Astrophysics and Statistics) is a public rapid binary population synthesis code. COMPAS generates populations of isolated stellar binaries under a set of parametrised assumptions in order to allow comparisons against observational data sets, such as those coming from gravitational-wave observations of merging compact remnants. It includes a number of tools for population processing in addition to the core binary evolution components. COMPAS is publicly available via the github repository https://github.com/TeamCOMPAS/COMPAS/, and is designed to allow for flexible modifications as evolutionary models improve. This paper describes the methodology and implementation of COMPAS. It is a living document which will be updated as new features are added to COMPAS; the current document describes COMPAS v02.21.00.

MODEST-1: Integrating stellar evolution and stellar dynamics

New Astronomy, 2003

We summarize the main results from MODEST-1, the first workshop on MOdeling DEnse STellar systems. Our goal is to go beyond traditional population synthesis models, by introducing dynamical interactions between single stars, binaries, and multiple systems. The challenge is to define and develop a software framework to enable us to combine in one simulation existing computer codes in stellar evolution, stellar dynamics, and stellar hydrodynamics. With this objective, the workshop brought together experts in these three fields, as well as other interested astrophysicists and computer scientists. We report here our main conclusions, questions and suggestions for further steps toward integrating stellar evolution and stellar (hydro)dynamics.

Numerical Evolution of Single, Binary and Triple Stars

Proceedings of the International Astronomical Union, 2007

I discuss my stellar evolution codeEvin the context of simulations of large clusters of stars. It has long been able to handle single stars, and also binary stars up to a point. That point is far beyond what other codes are able to do, but well short of what is necessary for believable simulations. A recent version,Ev(Twin), can in principle deal with the contact phase of binary evolution, but it is not yet clear what the physical interaction is that needs to be simulated.An upgrade, which I hope will be only a few lines, should allow it to follow Kozai cycles with tidal friction, a process that strongly influences the orbital period of close pairs that reside within wide, non-coplanar triples. However, there are many substantial gaps in the physics of even single stars, let alone binaries or triples.

A Large Stellar Evolution Database for Population Synthesis Studies. III. Inclusion of the Full Asymptotic Giant Branch Phase and Web Tools for Stellar Population Analyses

The Astronomical Journal, 2007

Stellar evolution tracks and isochrones are key inputs for a wide range of astrophysical studies; in particular, they are essential to the interpretation of photometric and spectroscopic observations of resolved and unresolved stellar populations. We have made available to the astrophysical community a large, homogenous database of up-to-date stellar tracks and isochrones, and a set of programs useful in population synthesis studies. In this paper we first summarize the main properties of our stellar model database (BaSTI) already introduced in Pietrinferni et al. (2004) and Pietrinferni et al. (2006). We then discuss an important update of the database, i.e., the extension of all stellar models and isochrones until the end of the thermal pulses along the Asymptotic Giant Branch. This extension of the library is particularly relevant for stellar population analyses in the near-infrared, or longer wavelengths, where the contribution to the integrated photometric properties by cool and bright Asymptotic Giant Branch stars is significant. A few comparisons with empirical data are also presentend and briefly discussed. We then present three web-tools that allow an interactive access to the database, and make possible to compute user-specified evolutionary tracks, isochrones, stellar luminosity functions, plus synthetic Color-Magnitude-Diagrams and integrated magnitudes for arbitrary Star Formation Histories. All these web tools are available at the BaSTI database official site: http://www.oa-teramo.inaf.it/BASTI.

Revisiting the common envelope evolution in binary stars: A new semianalytic model for N -body and population synthesis codes

Physical Review D

We present a novel way of modeling common envelope evolution in binary and few-body systems. We consider the common envelope inspiral as driven by a drag force with a power-law dependence in relative distance and velocity. The orbital motion is resolved either by direct N-body integration or by solving the set of differential equations for the orbital elements as derived using perturbation theory. Our formalism can model the eccentricity during the common envelope inspiral, and it gives results consistent with smoothed particles hydrodynamical simulations. We apply our formalism to common envelope events from binary population synthesis models and find that the final eccentricity distribution resembles the observed distribution of post-common-envelope binaries. Our model can be used for time-resolved commonenvelope evolution in population synthesis calculations or as part of binary interactions in direct N-body simulations of star clusters.

BASTI: an interactive database of updated stellar evolution models

2006

We present a new database of stellar evolution models for a large range of masses and chemical compositions, based on an up-to-date theoretical framework. We briefly discuss the physical inputs and the assumptions adopted in computing the stellar models. We explain how to access to the on-line archive and briefly discuss the interactive WEB tools that can be used to compute user-specified evolutionary tracks/isochrones/luminosity functions. The future developments of this database are also outlined.

A high-resolution stellar library for evolutionary population synthesis

Monthly Notices of the Royal Astronomical Society, 2005

We present a library of 1654 high-resolution stellar spectra, with a sampling of 0.3Å and covering the wavelength range from 3000 to 7000Å. The library was computed with the latest improvements in stellar atmospheres, incorporating non-LTE line-blanketed models for hot, massive (T eff 27500 K) and line-blanketed models for cool (3000 K T eff 4500 K) stars. The total coverage of the grid is 3000 K T eff 55000 K and -0.5 log g 5.5, for four chemical abundance values: twice solar, solar, half solar and 1/10 solar. Evolutionary synthesis models using this library are presented in a companion paper. We tested the general behavior of the library by calculating and comparing equivalent widths of numerous H and HeI lines, and some of the commonly used metallic indices. We also compared the library with the empirical libraries STELIB and Indo-US. The full set of the synthetic stellar spectra is available from our websites (http://www.iaa.csic.es/∼rosa and

Transition of the stellar initial mass function explored using binary population synthesis

Monthly Notices of the Royal Astronomical Society: Letters, 2013

The stellar initial mass function (IMF) plays a crucial role in determining the number of surviving stars in galaxies, the chemical composition of the interstellar medium, and the distribution of light in galaxies. A key unsolved question is whether the IMF is universal in time and space. Here we use state-of-the-art results of stellar evolution to show that the IMF of our Galaxy made a transition from an IMF dominated by massive stars to the present-day IMF at an early phase of the Galaxy formation. Updated results from stellar evolution in a wide range of metallicities have been implemented in a binary population synthesis code, and compared with the observations of carbon-enhanced metal-poor (CEMP) stars in our Galaxy. We find that applying the present-day IMF to Galactic halo stars causes serious contradictions with four observable quantities connected with the evolution of AGB stars. Furthermore, a comparison between our calculations and the observations of CEMP stars may help us to constrain the transition metallicity for the IMF which we tentatively set at [Fe/H] ≈ −2. A novelty of the current study is the inclusion of mass loss suppression in intermediate-mass AGB stars at low-metallicity. This significantly reduces the overproduction of nitrogen-enhanced stars that was a major problem in using the high-mass star dominated IMF in previous studies. Our results also demonstrate that the use of the present day IMF for all time in chemical evolution models results in the overproduction of Type I.5 supernovae. More data on stellar abundances will help to understand how the IMF has changed and what caused such a transition.