Getting Started

Installation

While it is possible to install radvel inside a minimal Python environment like that built-in to Mac OSX, we recommend first installing a scientific Python environment such as Anaconda or Miniconda.

Install radvel using pip:

$ pip install radvel

Make sure that pdflatex is installed and in your system’s path. You can get pdflatex by installing the TexLive package or other LaTeX distributions. By default it is expected to be in your system’s path, but you may specify a path to pdflatex using the --latex-compiler option at the radvel report step.

If you are running OSX, and want to perform Gaussian Process likelihood computations in parallel, you may need to perform some additional installation steps. See multiprocessing on OSX.

If you wish to use the celerite GP kernels you will also need to install celerite. See the celerite install instructions.

Example Fit

Test your installation by running through one of the included examples. We will use the radvel command line interface to execute a multi-planet, multi-instrument fit.

The radvel binary should have been automatically placed in your system’s path by the pip command (see Installation). If your system can not find the radvel executable then try running python setup.py install from within the top-level radvel directory.

First lets look at radvel --help for the available options:

$ radvel --help
usage: RadVel [-h] [--version] {fit,plot,mcmc,derive,bic,table,report} ...

RadVel: The Radial Velocity Toolkit

optional arguments:
  -h, --help            show this help message and exit
  --version             Print version number and exit.

subcommands:
  {fit,plot,mcmc,derive,bic,table,report}

Here is an example workflow to run a simple fit using the included HD164922.py example configuration file. This example configuration file can be found in the example_planets subdirectory on the GitHub repository page.

Perform a maximum-likelihood fit. You almost always will need to do this first:

$ radvel fit -s /path/to/radvel/example_planets/HD164922.py

By default the results will be placed in a directory with the same name as your planet configuration file (without .py, e.g. HD164922). You may also specify an output directory using the -o flag.

After the maximum-likelihood fit is complete the directory should have been created and should contain one new file: HD164922/HD164922_post_obj.pkl. This is a pickle binary file that is not meant to be human-readable but lets make a plot of the best-fit solution contained in that file:

$ radvel plot -t rv -s /path/to/radvel/example_planets/HD164922.py

This should produce a plot named HD164922_rv_multipanel.pdf that looks something like this.

Next lets perform the Markov-Chain Monte Carlo (MCMC) exploration to assess parameter uncertainties.

$ radvel mcmc -s /path/to/radvel/example_planets/HD164922.py

Once the MCMC chains finish running there will be another new file called HD164922_mcmc_chains.csv.tar.bz2. This is a compressed csv file containing the parameter values and likelihood at each step in the MCMC chains.

Now we can update the RV time series plot with the MCMC results and generate the full suite of plots.

$ radvel plot -t rv corner trend -s /path/to/radvel/example_planets/HD164922.py

We can summarize our analysis with the radvel report command.

$ radvel report -s /path/to/radvel/example_planets/HD164922.py

which creates a LaTeX document and corresponding PDF to summarize the results. Note that this command assembles values and plots that have been computed through other commands, if you want to update, rerun the previous commands before reruning radvel report

The report PDF will be saved as HD164922_results.pdf. It should contain a table reporting the parameter values and uncertainties, a table summarizing the priors, the RV time-series plot, and a corner plot showing the posterior distributions for all free parameters.

Optional Features

Combine the measured properties of the RV time-series with the properties of the host star defined in the setup file to derive physical parameters for the planetary system. Have a look at the epic203771098.py example setup file to see how to include stellar parameters.

$ radvel derive -s /path/to/radvel/example_planets/HD164922.py

Generate a corner plot for the derived parameters. This plot will also be included in the summary report if available.

$ radvel plot -t derived -s /path/to/radvel/example_planets/HD164922.py

Perform a model comparison testing models eliminating different sets of planets, their eccentricities, and RV trends. If this is run a new table will be included in the summary report.

$ radvel ic -t nplanets e trend -s /path/to/radvel/example_planets/HD164922.py

Generate and save only the TeX code for any/all of the tables.

$ radvel table -t params priors ic_compare derived -s /path/to/radvel/example_planets/HD164922.py