4 research outputs found
Characterization of stellar companion from high-contrast long-slit spectroscopy data: The EXtraction Of SPEctrum of COmpanion (EXOSPECO) algorithm
High-contrast long-slit spectrographs can be used to characterize exoplanets.
High-contrast long-slit spectroscopic data are however corrupted by stellar
leakages which largely dominate other signals and make the process of
extracting the companion spectrum very challenging. This paper presents a
complete method to calibrate the spectrograph and extract the signal of
interest.
The proposed method is based on a flexible direct model of the high-contrast
long-slit spectroscopic data. This model explicitly accounts for the
instrumental response and for the contributions of both the star and the
companion. The contributions of these two components and the calibration
parameters are jointly estimated by solving a regularized inverse problem. This
problem having no closed-form solution, we propose an alternating minimization
strategy to effectively find the solution.
We have tested our method on empirical long-slit spectroscopic data and by
injecting synthetic companion signals in these data. The proposed
initialization and the alternating strategy effectively avoid the
self-subtraction bias, even for companions observed very close to the
coronagraphic mask. Careful modeling and calibration of the angular and
spectral dispersion laws of the instrument clearly reduce the contamination by
the stellar leakages. In practice, the outputs of the method are mostly driven
by a single hyper-parameter which tunes the level of regularization of the
companion SED.Comment: Paper under review by Astronomy & Astrophysic