Exoplanets and Stellar Physics

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PlatoSim: an end-to-end PLATO camera simulator for modelling high-precision space-based photometry

Astronomy and Astrophysics EDP Sciences 681 (2024) A18

Authors:

N Jannsen, J De Ridder, D Seynaeve, S Regibo, R Huygen, P Royer, C Paproth, D Grießbach, R Samadi, Dr Reese, M Pertenais, E Grolleau, R Heller, Sm Niemi, J Cabrera, A Börner, S Aigrain, J Mccormac, P Verhoeve, P Astier, N Kutrowski, B Vandenbussche, A Tkachenko, C Aerts

Abstract:

Context. PLAnetary Transits and Oscillations of stars (PLATO) is the ESA M3 space mission dedicated to detect and characterise transiting exoplanets including information from the asteroseismic properties of their stellar hosts. The uninterrupted and high-precision photometry provided by space-borne instruments such as PLATO require long preparatory phases. An exhaustive list of tests are paramount to design a mission that meets the performance requirements and, as such, simulations are an indispensable tool in the mission preparation.

Aims. To accommodate PLATO’s need of versatile simulations prior to mission launch that at the same time describe innovative yet complex multi-telescope design accurately, in this work we present the end-to-end PLATO simulator specifically developed for that purpose, namely PlatoSim. We show, step-by-step, the algorithms embedded into the software architecture of PlatoSim that allow the user to simulate photometric time series of charge-coupled device (CCD) images and light curves in accordance to the expected observations of PLATO.

Methods. In the context of the PLATO payload, a general formalism of modelling, end-to-end, incoming photons from the sky to the final measurement in digital units is discussed. According to the light path through the instrument, we present an overview of the stellar field and sky background, the short- and long-term barycentric pixel displacement of the stellar sources, the cameras and their optics, the modelling of the CCDs and their electronics, and all main random and systematic noise sources.

Results. We show the strong predictive power of PlatoSim through its diverse applicability and contribution to numerous working groups within the PLATO mission consortium. This involves the ongoing mechanical integration and alignment, performance studies of the payload, the pipeline development, and assessments of the scientific goals.

Conclusions. PlatoSim is a state-of-the-art simulator that is able to produce the expected photometric observations of PLATO to a high level of accuracy. We demonstrate that PlatoSim is a key software tool for the PLATO mission in the preparatory phases until mission launch and prospectively beyond.

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Modeling Noncondensing Compositional Convection for Applications to Super-Earth and Sub-Neptune Atmospheres

The Astrophysical Journal American Astronomical Society 961:1 (2024) 35

Authors:

Namrah Habib, Raymond T Pierrehumbert
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ATMOSPHERIX: I- an open source high-resolution transmission spectroscopy pipeline for exoplanets atmospheres with SPIRou

Monthly Notices of the Royal Astronomical Society, Volume 527, Issue 1, pp.544-565

Authors:

Baptiste Klein, Florian Debras, Jean-Francois Donati et al.

Abstract:

Atmospheric characterization of exoplanets from the ground is an actively growing field of research. In this context, we have created the ATMOSPHERIX consortium: a research project aimed at characterizing exoplanets atmospheres using ground-based high-resolution spectroscopy. This paper presents the publicly available data analysis pipeline and demonstrates the robustness of the recovered planetary parameters from synthetic data. Simulating planetary transits using synthetic transmission spectra of a hot Jupiter that were injected into real SPIRou observations of the non-transiting system Gl 15 A, we show that our pipeline is successful at recovering the planetary signal and input atmospheric parameters. We also introduce a deep learning algorithm to optimize data reduction which proves to be a reliable, alternative tool to the commonly used principal component analysis. We estimate the level of uncertainties and possible biases when retrieving parameters such as temperature and composition and hence the level of confidence in the case of retrieval from real data. Finally, we apply our pipeline onto two real transits of HD 189733 b observed with SPIRou and obtain similar results than in the literature. In summary, we have developed a publicly available and robust pipeline for the forthcoming studies of the targets to be observed in the framework of the ATMOSPHERIX consortium, which can easily be adapted to other high resolution instruments than SPIRou (e.g. VLT-CRIRES, MAROON-X, ELT-ANDES).
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ATMOSPHERIX: II- Characterizing exoplanet atmospheres through transmission spectroscopy with SPIRou

Monthly Notices of the Royal Astronomical Society, Volume 527, Issue 1, pp.566-582

Authors:

Florian Debras, Baptiste Klein, Jean-Francois Donati et al.

Abstract:

In a companion paper, we introduced a publicly available pipeline to characterize exoplanet atmospheres through high-resolution spectroscopy. In this paper, we use this pipeline to study the biases and degeneracies that arise in atmospheric characterization of exoplanets in near-infrared ground-based transmission spectroscopy. We inject synthetic planetary transits into sequences of SPIRou spectra of the well known M dwarf star Gl 15 A, and study the effects of different assumptions on the retrieval. We focus on (i) mass and radius uncertainties, (ii) non-isothermal vertical profiles, and (iii) identification and retrieval of multiple species. We show that the uncertainties on mass and radius should be accounted for in retrievals and that depth-dependent temperature information can be derived from high-resolution transmission spectroscopy data. Finally, we discuss the impact of selecting wavelength orders in the retrieval and the issues that arise when trying to identify a single species in a multispecies atmospheric model. This analysis allows us to understand better the results obtained through transmission spectroscopy and their limitations in preparation to the analysis of actual SPIRou data.
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The polarimetric performance of HARPS3 and its impact on the Terra Hunting Experiment scheduling

Proceedings of the SPIE, Volume 13096, id. 130968C 11 pp. (2024)

Authors:

Patrick Dorval, Ioannis Politopoulos, Belinda Nicholson, Rik ter Horst, Casper Farret Jentink, Baptiste Klein et al.

Abstract:

The main goal of the third iteration of the High Accuracy Radial velocity Planet Searcher (HARPS3) is to search for Earth-like planets over a ten-year programme. As part of this search, spectropolarimetric observations have been envisioned foreseeing the need for new ways to reduce stellar activity jitter which obscures the 10 cm/sec radial velocity signal of such planets. HARPS3 has thus been designed with an insertable polarimetric sub-unit. This sub-unit consists of two superachromatic polymer retarders, one quarter-wave and one half-wave, to separately detect all Stokes parameters of a target, as well as a polarimetric beam splitter to separate the parallel polarimetric beams by 30 mm to feed the science fibers. In this paper we report on the currently nonfunctional polarimetric sub-unit of the HARPS3 spectrograph and discuss the upgrade expected before commissioning that will fix current issues. We discuss the possible observation schedule of polarimetric observations for the Terra Hunting Experiment and the potential impacts of polarimetric observations on mitigating stellar radial velocity jitter.
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