Exoplanets Molecular Atmospheric Composition

Project Information

ExoMAC

Grant agreement ID: 895525

DOI

10.3030/895525

Project closed

EC signature date 20 March 2020

Start date 9 November 2020

End date 8 November 2022

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 160 932,48

EU contribution

€ 160 932,48

Coordinated by

INSTITUTO DE ASTROFISICA DE CANARIAS
Spain

Periodic Reporting for period 1 - ExoMAC (Exoplanets Molecular Atmospheric Composition)

Reporting period: 2020-11-09 to 2022-11-08

Summary of the context and overall objectives of the project

The ExoMAC project aimed primarily at improving our understanding of exoplanetary atmospheres by exploiting synergies between different types of observations and techniques, in particular by leveraging the information content of low- and high-resolution spectroscopic data obtained from space and ground-based telescopes (WP2: C&C Analyses).
A second course of action was the discovery and characterization of new exoplanets among TESS candidates, with a focus on identifying prime targets for atmospheric observations with the JWST and Ariel space missions (WP3: TESS classification).

The project aimed thus to overcome the two main limitations in the field of characterization of exoplanets:
1. The fragmentation of data analysis for individual planets that limits scientific inferences;
2. The exiguity of the statistical sample that prevents us from understanding the global picture.

I addressed these two limitations through the following scientific objectives:
SO1. [WP2] The complete and consistent analyses of individual planets for measuring the absolute abundances of all the main carbon and oxygen-bearing molecules (H2O, CO, CO2 and CH4), metallicity down to 0.5 dex and precise C/O down to ∼0.1 dex in a handful of exoplanet atmospheres. The C&C analyses can provide the first empirical constraints on the possible formation and evolutionary paths of exoplanets;
SO2. [WP3] The development of a convolutional neural network for the automated classification of newly-released TESS light-curves for the discovery and classification of new exoplanet populations. This CNN will lead to the discovery of 104 transiting exoplanets, among which to select the prime targets for spectroscopic characterization with current and next-generation facilities.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

WP1: Project Management
The scientific management was done both by the experienced researcher and the host. All decisions have been agreed by both parties. There was adequate support from the administrative staff at the IAC.
The researcher was readily integrated within the host department, including the completion of bureaucracy, set up of the working environment and access to computing resources. The researcher has developed collaborations with other members of the "Exoplanets and Astrobiology" group at the IAC, mainly postdocs and PhD students. However, in-person interactions during the first year of contract were severely limited due to sanitary measures related to the covid-19 pandemic. These restrictions have significantly slowed down the transfer of knowledge and, consequently, the development of the scientific tasks.
The researcher was also involved in external collaborations, particularly the CARMENES and MuSCAT2 consortia, and strengthened his involvement within and JWST Early Release Science programs, and the Ariel and PLATO mission consortia.
WP2: C&C analyses
The main task of WP2 was to perform complete and consistent (C&C) analyses of the multiple datasets available to characterize exoplanet atmospheres. This work led to publication of our first milestone article:
1. Morello, G., et al. (2022) "The strange case of Na I in the atmosphere of HD 209458 b. Reconciling low- and high-resolution spectroscopic observations", A&A, 657, A97 - doi:10.1051/0004-6361/202141642
In this paper, we have reconciled the discrepant results found in previous literature regarding the presence of sodium in the atmosphere of an iconic exoplanet. The controversy was mainly based on HST/STIS and VLT/ESPRESSO datasets. The key advance in our analysis was consistent spectral modeling of both low- and high-resolution data, taking into account the Rossiter-McLaughlin (RM) effect due to stellar rotation along with absorption through the planetary atmosphere.
WP3: TESS classification
The initial plan for WP3 was to improve the automated classification pipelines of targets observed by TESS, starting from the neural network Astronet. The scientific objective was to enhance the discoveries of amenable exoplanets to characterize their atmospheres using JWST, and later Ariel, observations. Due to the overwhelming success of TESS Follow-up Programs (TFOP), and considering that more favorable targets are likely to be discovered earlier, we changed our plan of action with a more immediate one. The researcher joined the MuSCAT2 and CARMTESS collaborations, which are part of the TFOP, and performed observations, data analysis, modeling and writing tasks. He led a first-author paper (under review, first version available on arXiv) on the validation of two rocky planets orbiting around M dwarfs in less than one day, which are also among the top 20 targets for emission spectroscopy with the JWST.
WP4: Communication & Dissemination
The scientific results were published in peer-reviewed journals, mostly with an impact factor >5 (A&A, AJ, MNRAS), and in two Research Notes of the American Astronomical Society (RNAAS). They were also presented in international conferences and workshops.
WP5: Training and Transfer of Knowledge
The researcher has learned various techniques for high-resolution spectroscopy of exoplanet atmospheres, although with significant delays mostly attributable to the covid-19 (as previously explained). In exchange, he shared his expertise on the analysis and modeling of low-resolution spectroscopic data. Recently, he invited several members from the JWST consortium to start a promising collaboration with the IAC group. We are now co-writing several JWST proposals

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The C&C methodology is in itself innovative. Most researchers tend to analyse each dataset independently, or to analyse a combined spectrum from those observed with different instruments either in transit or in eclipse. Inverse retrieval algorithms are routinely used to constrain the atmospheric properties from their transmission or emission spectrum. Consistent retrievals that take into account the transmission and emission spectra (and phase-curves) simultaneously are a needed software development. We will adopt an updated version of T - REx34,35 to enable simultaneous transmission+emission retrieval, coupled with deep convolutional generative adversarial networks36 to speed up the likelihood sampling. Beyond technical aspects, the combination of low- and high-resolution spectroscopy appears to be exceptionally powerful for measuring precise chemical abundances and elemental ratios, thus allowing a meaningful comparison with the predictions of evolutionary models.
The concept of an automated pipeline for classification of transit-like signals is not intrinsically novel. However, there is no reliable classification pipeline for the TESS light-curves. The vast number of available TESS light- curves is expected to allow us the discovery of many new “rare” planetary architectures. We will propose a novel CNN architecture that enables more complex than binary classification.
The action has had a positive impact on the researcher's prospective career, significantly expanding his collaboration network and increasing his publications rate as a co-author. Additionally, the researcher acquired new leading roles, such as Leader of the PLATO WP122400 on Stellar Limb-Darkening and of the "Ariel - Activity Correction for Planetary Spectra" sub-working group. However, the next steps in the researcher's career are still uncertain.

We developed new methods to exploit that will be largely used in the forthcoming years to analyse low- and high-resolution spectroscopy data.

Orbital periods

The strange case of Na I in the atmosphere of HD 209458 b (1)

The strange case of Na I in the atmosphere of HD 209458 b (2)

ExoMAC Newton comic image

Transiting ExoPLANETS