Extraction Of SPEctrum of COmpanion in long-slit spectroscopy data

Exospeco is a Julia package used in high-contrast imaging for extracting the sub-stellar companion SED in long-slit spectroscopy data.

Installation

To install the package, hit the ] key to activate the Pkg mode of julia and enter the following line:

add https://github.com/SJJThe/Exospeco

Usage

Geometric calibration

The first step toward using Exospeco is to obtain the geometric calibration. Either load pre-existing angular separations map rho in milliarcseconds, wavelengths map lambda in nanometers and mask of valid data mask into a GeoCalib structure:

using ExospecoCalibration

Geo = GeoCalib(rho, lambda, mask)

or use the ExospecoCalibration to generate these maps from a calibration data d_cal and a bad pixels map bpm:

using ExospecoCalibration

pol_rho = (2,1)
pol_lambda = (2,5)
Geo = calibrate_geometry(d_cal, bpm; spatial_law_carac=pol_rho, spectral_law_carac=pol_lambda)

If a geometric calibration already exists, it is possible to load it by:

path_to_struct = "..."
Geo = readfits(GeoCalib, path_to_struct)

Thanks to this calibration, it is possible to build a CalibratedLSSData structure given a frame d of LSS data and their respective weights w:

using Exospeco

D = CalibratedLSSData(d, w, Geo)

Initialization

The next step is to initialize the parameters of the problem that will be estimated by Exospeco, that is x the star SED, y the on-axis PSF, nu_star the angular separation between the star and the center of the coronagraphic mask, z the companion SED and nu_comp the parameters of the off-axis PSF:

# number of samples of x, y, z
N_x = 1024
N_y = 1024
N_z = 1024
# angular separation from companion to center of coronagraphic mask
rho_comp = -800*Exospeco.mas

(x_init, y_init, nu_star_init, z_init,
 nu_comp_init) = initialize(N_x, N_y, N_z, D, rho_comp; wordy=true)

Estimation of the parameters

Exospeco needs the values of the hyper-parameters mu_x and mu_z corresponding to the levels of the star SED regularization and the companion SED regularization:

mu_x = 1e1
mu_z = 5e4

(x, y, nu_star, z,
 nu_comp) = exospeco(x_init, y_init, nu_star_init, z_init, nu_comp_init, D, 
                     mu_x, mu_z; delay_auto_calib=true, 
                     nonnegative=true, maxiter=20, alg_tol=(0.0,1e-3), 
                     wordy=true)