GitHub release Documentation Status Updates

Advanced Webb Exposure SIMulator for SOSS

Authors: Joe Filippazzo, Kevin Volk, Jonathan Fraine, Michael Wolfe

This pure Python 3.5+ package produces simulated time-series data for the Single Object Slitless Spectroscopy (SOSS) mode of the NIRISS instrument onboard the James Webb Space Telescope.

Additional resources:


The best way to install awesimsoss is

conda install -c jfilippazzo awesimsoss

You can also do it with

git clone
cd awesimsoss
conda env create --name awesimsoss -f environment.yml
conda activate awesimsoss
python develop

Simulating SOSS Observations

Given a 1D spectrum of a target, this module produces a 2D SOSS ramp image with the given number of groups and integrations. For example, if I want to produce 5 integrations of 3 groups each for a J=9 A0 star as seen through SOSS, my code might look like:

# Imports
from awesimsoss import TSO
from hotsoss import STAR_DATA

# Initialize simulation
tso256_clear = TSO(ngrps=3, nints=5, star=STAR_DATA)

# Run it and make a plot
The output trace

The plot method generates an interactive figure of counts, SNR, and saturation values for the entire exposure as well as the wavelength value at each pixel for each order and a slider to inspect each frame in the cross dispersion direction.

The SUBSTRIP256 subarray is the default but the SUBSTRIP96 subarray and FULL frame configurations are also supported:

tso96_clear = TSO(ngrps=3, nints=5, star=STAR_DATA, subarray='SUBSTRIP96')
tso2048_clear = TSO(ngrps=3, nints=5, star=STAR_DATA, subarray='FULL')

The default filter is CLEAR but you can also simulate observations with the F277W filter like so:

tso256_f277w = TSO(ngrps=3, nints=5, star=STAR_DATA, filter='F277W')

Simulated Planetary Transits

The example above was for an isolated star though. To include a planetary transit we must additionally provide a transmission spectrum and the orbital parameters of the planet.

Here is a sample transmission spectrum generated with PandExo:

from hotsoss import PLANET_DATA
The input transmission spectrum

And here are some orbital parameters for our planetary system using batman:

# Simulate star with transiting exoplanet by including transmission spectrum and orbital params
import batman
tso_transit = TSO(ngrps=3, nints=5, star=STAR_DATA)
params = batman.TransitParams()
params.t0 = 0. # time of inferior conjunction
params.per = 5.7214742 # orbital period (days)
params.a = 7.92 # semi-major axis (in units of stellar radii)
params.rp = 0.1 # radius ratio for Jupiter orbiting the Sun = 89.8 # orbital inclination (in degrees)
params.ecc = 0. # eccentricity
params.w = 90. # longitude of periastron (in degrees) p
params.limb_dark = 'quadratic' # limb darkening profile to use
params.u = [0.1,0.1] # limb darkening coefficients

tmodel = batman.TransitModel(params, tso_transit.time)
tmodel.teff = 3500 # effective temperature of the host star
tmodel.logg = 5 # log surface gravity of the host star
tmodel.feh = 0 # metallicity of the host star

Now the code to generate a simulated planetary transit around our star might look like:

tso_transit.simulate(planet=PLANET_DATA, tmodel=tmodel)

We can write this to a FITS file directly ingestible by the JWST pipeline with: