Long-slit spectroscopy characterization of substellar objects with the EXOSPEC algorithm

Samuel Thé; Éric Thiébaut; Loïc Denis; Ferréol Soulez; Maud Langlois

doi:10.1117/12.2630171

29 August 2022 Long-slit spectroscopy characterization of substellar objects with the EXOSPEC algorithm

Samuel Thé, Éric Thiébaut, Loïc Denis, Ferréol Soulez, Maud Langlois

Proceedings Volume 12185, Adaptive Optics Systems VIII; 121853Q (2022) https://doi.org/10.1117/12.2630171
Event: SPIE Astronomical Telescopes + Instrumentation, 2022, Montréal, Québec, Canada

Conference Poster

Abstract

To better understand the phenomena which take place during the formation and evolution of substellar objects, it is necessary to have access to their spectra. For that purpose, the SPHERE-IRDIS long-slit spectroscopy mode, allied with extreme adaptive optics and coronagraphy, has been designed to spectrally characterize substellar objects in the near-infrared (J, H and K bands). Residual aberrations are however responsible for stellar leaks in the form of dispersed speckles that are much brighter than the spectrum of the faint companion. Post-processing methods are thus required to extract the companion spectrum. Most existing methods consist in first subtracting the stellar contribution from the data and then measuring the companion spectrum in the residuals. We are developing a novel approach, named EXOSPEC and based on the inverse problems framework, which jointly estimates the two contributions; that of the star and that of the companion. Exospec exploits the differences of behavior of their spatio-spectral distributions in the data in order to disentangle them. The parameters of the instrumental model, which is a critical part of the approach, are refined by means of self-calibration directly from the science data. Other parameters of the problem are automatically tuned, leading to a fully unsupervised method. Compared to current methods, EXOSPEC is able to extract companion spectra with less contamination by the stellar leaks and succeeds in harder cases (e.g., closer to the mask). The benefits of our approach is demonstrated on real datasets.

Citation Download Citation

Samuel Thé, Éric Thiébaut, Loïc Denis, Ferréol Soulez, and Maud Langlois "Long-slit spectroscopy characterization of substellar objects with the EXOSPEC algorithm", Proc. SPIE 12185, Adaptive Optics Systems VIII, 121853Q (29 August 2022); https://doi.org/10.1117/12.2630171

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