51 Peg

This section is a hands-on tutorial on how to make a simple run. We use the 51 Peg RV data available on GitHub.

Data

We need to set up our working directory with two subfolders, datafiles and datalogs.

datafiles will contain our RV catalogues. For each target or system we create a subfolder with the system name. In this case, 51Peg. Inside, we create a second subfolder, named RV, which will contain the data to be read.

We copy-paste the file downloaded from GitHub into /datafiles/51Peg/RV/.

📂working_directory
 ┣ 📜mini_test.py
 ┣ 📂datafiles
 ┃ ┣ 📂51Peg
 ┃ ┃ ┗ 📂RV
 ┃ ┃ ┃ ┗ 📜51peg.vels
 ┣ 📂datalogs
 ┃ ┣ 📂51Peg
 ┃ ┃ ┗ 📂run_1

Setting up EMPEROR

Under our working directory, we create a python file named mini_test. First, we import the library and start our simulation:

import astroemperor as emp
import numpy as np
np.random.seed(1234)


sim = emp.Simulation()

Setting the engine

For this example, we will use reddemcee, with 10 temperatures, 256 walkers, 2048 sweeps each of 1 step:

sim.set_engine('reddemcee')
sim.engine_config['setup'] = [10, 256, 2048, 1]

Setting the model

We feed the name of the instrument (optional), as well as the starmass for calculating the minimum-mass and semi-major axis. We will use the Keplerian parameterisation (P, K, \(\phi\), \(e_{s}\), \(e_{c}\)). We add some boundaries to speed up the process, and add some initial positions:

sim.instrument_names_RV = ['LICK']
sim.starmass = 1.12
sim.keplerian_parameterisation = 1


sim.add_condition(['Period 1', 'limits', [3, 5]])
sim.add_condition(['Amplitude 1', 'limits', [45, 60]])

sim.add_condition(['Offset 1', 'limits', [-10., 10.]])

sim.add_condition(['Period 1', 'init_pos', [4.1, 4.3]])
sim.add_condition(['Amplitude 1', 'init_pos', [50, 60]])

Plotting Options

We add some plotting options to speed up this test a little. We will only plot the posteriors for the cold chain, and two intermediate chains. Also, we won't use the arviz optional plots.

sim.plot_posteriors['temps'] = [0, 2, 6]
sim.plot_trace['plot'] = False

Finally, we read the data and run our simulation (it will take some minutes):

sim.load_data('51Peg')  # folder read from /datafiles/
sim.autorun(0, 1)