Issue |
A&A
Volume 678, October 2023
|
|
---|---|---|
Article Number | A77 | |
Number of page(s) | 19 | |
Section | Numerical methods and codes | |
DOI | https://doi.org/10.1051/0004-6361/202245565 | |
Published online | 09 October 2023 |
Characterization of stellar companions from high-contrast long-slit spectroscopy data
The EXtraction Of SPEctrum of COmpanion (EXOSPECO) algorithm
1
Université de Lyon, Université Lyon1, ENS de Lyon, CNRS,
Centre de Recherche Astrophysique de Lyon UMR 5574,
69230
Saint-Genis-Laval,
France
e-mail: samuel.the@univ-lyon1.fr, eric.thiebaut@univ-lyon1.fr
2
Université Jean-Monnet-Saint-Étienne, CNRS, Institut d’Optique Graduate School,
Laboratoire Hubert Curien UMR 5516,
42023
Saint-Étienne,
France
e-mail: loic.denis@univ-st-etienne.fr
Received:
28
November
2022
Accepted:
19
July
2023
Aims. High-contrast long-slit spectrographs can be used to characterize exoplanets. The resulting spectroscopic data are, however, corrupted by stellar leakages that 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.
Methods. 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. As this problem has no closed-form solution, we propose an alternating minimization strategy to effectively find the solution.
Results. We 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 that tunes the level of regularization of the companion’s spectral energy distribution (SED).
Key words: infrared: planetary systems / methods: data analysis / techniques: imaging spectroscopy / instrumentation: spectrographs / instrumentation: adaptive optics
© The Authors 2023
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
This article is published in open access under the Subscribe to Open model. Subscribe to A&A to support open access publication.
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.