Icarus

Icarus is a stellar binary light curve synthesis tool initially developed by Rene Breton while being a postdoctoral fellow at the University of Toronto in the research group of Marten van Kerkwijk.

Icarus provides a set of basic tools that:

1. Generates a star given some basic binary parameters

   1.1. Solves the gravitational potential equation

   1.2. Creates a discretized stellar grid

   1.3. Populates the stellar grid with physical parameters (temperature, surface gravity, etc.)

2. Evaluates the outcoming flux from the star given an observer's point of view (i.e. orbtial phase and orbital orientation)

The code is compartimented in different layers:

1. The stellar surface solver

   1.1. The primitives generator of the discretized stellar grid: the code currently uses a triangular tessellation based the subdivision of an icosahedron. The primitives (vertices, face association, etc.) can be read from pre-calculated values stored in a file or dynamically generated using the external program pygts, which is distributed separately and not essential to Icarus.

   1.2. The actual surface solver.

2. The flux calculator

   2.1. The actual flux calculator tools: integrated surface flux. Supported for different modes is already provided (spectroscopy, photometry, Doppler shifting, Doppler boosting).

   2.2. The flux calculator makes use of an atmosphere backend, which returns the specific intensities given a set of input parameters (temperature, surface gravity, velocity, etc.). The atmosphere backend can be anything (analytical blackbody, lookup table to an atmosphere model, etc.). The current backend reads data from NextGen atmosphere models (distributed separately).

3. The binary system super-class

   3.1. A super-class making use of the two above layers to treat with a "proper" binary, which sums the flux of each component and includes the calculation of eclipses, transits, partial occultations, etc.

The original aim of Icarus was to model the light curves (photometry and spectroscopy) of irradiated neutron star companions, hence the name Icarus (the Greek mythology hero who flew to close to the Sun and melting the wax off his wings). The flux calculator therefore supports the contribution of an external source of energy (from the other binary component) which contributes to increasing the dayside temperature of the modeled star.

Here are a short, non-exhaustive list of publications related to the binary light curve synthesis.

• Breton et al., 2012, ApJL, 748, 115
• Orosz, J. A., & Hauschildt, P. H. 2000, A&A, 364, 265
• Hendry, P. D., & Mochnacki, S. W. 1992, ApJ, 388, 603

Installation

Method 1: PyPI

1. Icarus is now distributed through PyPI. It sources the latest stable release. Simply do the following:

   pip install Icarus
   

   This will install Icarus into your current Python distribution tree. Note that you may need to use 'sudo' before the command in order to write into the destination directory. On the other hand, you may install Icarus locally into your $HOME/.local by doing the following:

   pip install --user Icarus
   

Method 2: GitHub

1. In order to fetch the bleading edge version of Icarus, please download it from the GitHub repository (http://icarus.renebreton.org).

   1.1. You may download the package as a zip/tarball file.

   1.2. Or you can clone the repository using git (preferred option) which will allow you to stay in sync with the latest package version. To do so, go to the disk location where you want to install the package and type:

   git clone git://github.com/bretonr/Icarus.git
   cd Icarus
   

   To update you version to the latest GitHub version afterwards, go to the Icarus folder and type:

   git pull
   

2. From the Icarus folder, install Icarus by doing:

   python setup.py install
   

   This will install Icarus into your standard Python library directory. You may need to use 'sudo' in order to do so. On the other hand, you may install Icarus locally into your $HOME/.local by doing the following:

   python setup.py install --user
   

   Another option would be to simply add the build Icarus sub-folder to your $PYTHONPATH or copy it in a suitable location.

Atmosphere grids

You will need to source some atmosphere models or write your own atmosphere backend (e.g., to generate a blackbody SED). I cannot be of much help here unfortunately. I might try to write a basic blackbody backend eventually but I do not have time for now.

Requirements

I usually keep my packages up-to-date using Macport (on Mac) and Synoptic (on Ubuntu). Versions are provided for indicative purposes.

• Python (version > 2.7)
• Scipy
• Numpy
• astropy

Optional requirements

• Matplotlib (version > 1.1.0)
• PyGTS to generate surface geodesic primitives instead of reading the pre-generated ones. Also useful for calculating occulations and transits in eclipsing binaries.

If you use it

If you intend to use the code, please cite the paper in which it was first introduced: R. P. Breton, S. A. Rappaport, M. H. van Kerkwijk, J. A. Carter, "KOI 1224, a Fourth Bloated Hot White Dwarf Companion Found With Kepler", 2012, ApJL, 748, 115.

Also, please provide a link to the Icarus webpage.

The author, Rene Breton (superluminique+icarus@gmail.com), would be happy to receive feedback, constructive comments, bug fixes, etc., from people using Icarus. Unfortunately, only very limited support can be provided due to the author's busy research schedule.

Acknowledgements

Note that the author would like to acknowledge the immense help of Marten van Kerkwijk, who contributed via frequent discussions and who also provided a Fortran program to synthesize photometric light curves of irradiated binaries, which Icarus initially aimed to reproduce.

License

Please note that this project is protected against a 3-clause BSD license. Please see the content of the folder licenses/LICENSE.md for more information.