Europlanet Science Congress 2021
Virtual meeting
13 – 24 September 2021
Europlanet Science Congress 2021
Virtual meeting
13 September – 24 September 2021

EXO7

Future instruments to detect and characterise extrasolar planets and their environment.

Exoplanets are being discovered in large numbers thanks to recent and ongoing surveys using state-of-the-art instrumentation from the ground and from space. In the next years, new astronomical instruments will further scout our Galaxy to overcome the current observational biases in the search of alien worlds, to gain a deeper understanding of the chemical and physical properties of both exoplanets and their environments, and to unveil the processes of formation and evolution of planets and their atmospheres.

The goal of this session is to bring together the instrumentation and observational communities that are underpinning the future of this field. Contributions are invited to review ongoing programmes of exoplanet and circumstellar discs discovery and characterisation, to update on the progress of planned instrumentation programmes, and to present innovative ideas for future instrumentation.

Co-organized by MITM
Convener: Camilla Danielski | Co-conveners: Elodie Choquet, Paul Eccleston, Enzo Pascale, Subhajit Sarkar

Session assets

Discussion on Slack

Oral and Poster presentations and abstracts

Chairpersons: Camilla Danielski, Enzo Pascale, Paul Eccleston
Space-based
EPSC2021-572
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ECP
Billy Edwards, Marcell Tessenyi, Ian Stotesbury, Richard Archer, Max Joshua, and Ben Wilcock
The Twinkle Space Mission is a space-based observatory that has been conceived to measure the atmospheric composition of exoplanets, stars and solar system objects. Twinkle’s collaborative multi-year global survey programmes will deliver visible and infrared spectroscopy of thousands of objects within and beyond our solar system, enabling participating scientists to produce world-leading research in planetary and exoplanetary science. Twinkle’s growing group of international Founding Members have now started shaping the survey science programme within focused Science Teams and Working Groups and will soon be delivering their first papers.
 
Twinkle will have the capability to provide simultaneous broadband spectroscopic characterisation (0.5 - 4.5µm) of the atmospheres of several hundred bright exoplanets, covering a wide range of planetary types. It will also be capable of providing phase curves for hot, short-period planets around bright stars targets and of providing ultra-precise photometric light curves to accurately constrain orbital parameters, including ephemerides and TTVs/TDVs present in multi-planet systems.

I will present an overview of Twinkle’s mission status and discuss some example exoplanet surveys to highlight the broad range of targets the mission could observe, demonstrating the scientific potential of the spacecraft. I will also report on the work of the Twinkle exoplanet Science Team, showcasing their science interests and the studies into Twinkle’s capabilities that they have conducted since joining the mission.

How to cite: Edwards, B., Tessenyi, M., Stotesbury, I., Archer, R., Joshua, M., and Wilcock, B.: Twinkle: Update on the international, collaborative exoplanet survey, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-572, https://doi.org/10.5194/epsc2021-572, 2021.

EPSC2021-415
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ECP
Aarynn Carter

The James Webb Space Telescope (JWST), currently scheduled to launch in 2021, will dramatically advance our understanding of exoplanetary systems with its ability to directly image and characterise planetary-mass companions at wide separations through coronagraphy. Using state-of-the-art simulations of JWST performance, in combination with the latest evolutionary models, we present the most sophisticated simulated mass sensitivity limits of JWST coronagraphy to date. In particular, we focus our efforts towards observations of members within the nearby young moving groups 𝛽 Pictoris and TW Hya. These limits indicate that whilst JWST will provide little improvement towards imaging exoplanets at short separations, at wide separations the increase in sensitivity is dramatic. We predict JWST will be capable of imaging sub-Jupiter mass objects beyond ∼30 au, sub-Saturn mass objects beyond ∼50 au, and that beyond ∼100 au, JWST will be capable of directly imaging companions as small as 0.1 𝑀J − at least an order of magnitude improvement over the leading ground-based instruments. Probing this unexplored parameter space will be of immediate value to modelling efforts focused on planetary formation and population synthesis. JWST will also serve as an excellent complement to ground based observatories through its unique ability to characterise previously detected companions across the near- to mid-infrared for the first time.

How to cite: Carter, A.: Direct imaging of sub-Jupiter mass exoplanets with James Webb Space Telescope coronagraphy, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-415, https://doi.org/10.5194/epsc2021-415, 2021.

EPSC2021-822
Marie Ygouf, Charles A Beichman, Graça M Rocha, Joseph J Green, Jewell Jeffrey B, Gael M Roudier, Alexandra Greenbaum, Jarron Leisenring, Julien Girard, Laurent Pueyo, Marshall Perrin, Michael Meyer, Matthew De Furio, and Taichi Uyama
  The James Webb Space Telescope (JWST) will probe circumstellar environments at an unprecedented sensitivity. However, the performance of high-contrast imaging instruments is limited by the residual light from the star at close separations (<2-3”), where the incidence of exoplanets increases rapidly. There is currently no solution to get rid of the residual light down to the photon noise level at those separations, which may prevent some crucial discoveries.
  We are further developing and implementing a potentially game-changing technique of post-processing that does not require the systematic observation of a reference star, but instead directly uses data from the science target by taking advantage of the technique called “phase retrieval”. This technique is built on a Bayesian framework that provides a more robust determination of faint astrophysical structures around a bright source.
  This approach uses a model of instrument that takes advantage of prior information, such as data from wavefront sensing operations on JWST, to estimate instrumental aberrations and further push the limits of high-contrast imaging. With this approach, our goal is to improve the contrast that can be achieved with JWST instruments.
  We were awarded a JWST GO-Calibration proposal to implement, test and validate this approach on NIRCam imaging and coronagraphic imaging. This work will pave the way for the future space-based high-contrast imaging instruments such as the Nancy Grace Roman Space Telescope Coronagraph Instrument (Roman CGI). This technique will be crucial to make the best use of the telemetry data that will be collected during the CGI operations.
  
“© 2021 California Institute of Technology. Government sponsorship acknowledged. The research was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. This document has been reviewed and determined not to contain export controlled data.”

How to cite: Ygouf, M., Beichman, C. A., Rocha, G. M., Green, J. J., Jeffrey B, J., Roudier, G. M., Greenbaum, A., Leisenring, J., Girard, J., Pueyo, L., Perrin, M., Meyer, M., De Furio, M., and Uyama, T.: Realizing the Potential of JWST High Contrast Imaging with Coronagraphic Phase-Retrieval, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-822, https://doi.org/10.5194/epsc2021-822, 2021.

EPSC2021-546
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ECP
Evangelia Kleisioti, Dominic Dirkx, Marc Rovira-Navarro, and Matthew Kenworthy

Introduction

The discovery of the first extrasolar planets demonstrated that planets can form around other stars and be detected with current instrumentation. Since more than 200 moons exist in the Solar System, it is expected that they orbit exoplanets as well. Detecting an exomoon could set the next milestone in observations of exoplanetary systems.   

Tidal interactions between planets and their satellites can heat a satellite’s interior. The most evident example is Io, which is the most tidally active body in the Solar System. Since tidal dissipation depends on the orbital and physical properties of the system, if tidal heating is vigorous enough in exoplanetary systems, there is a chance that Tidally Heated Exomoons (THEMs; Peters and Turner 2015) are detectable with current instrumentation and/or the JWST in infrared (IR) wavelengths. As a direct result of tidal heating, spectral signatures of volcanic activity could also be a method of detecting THEMs (Oza et al. 2019). 

Two of the gas giant planet moon systems are in long-lived mean motion resonances (MMR) and it is expected that the latter would prevail in extrasolar systems as well. Taking the Jovian satellites as an archetype for an exomoon system around β Pictoris b, this would mean that an MMR between two or more exomoons would make them detectable for larger timescales, maintaining tidal activity over the lifetime of the system.

β Pictoris is a 23 Myr old star with a distance of 19.44 pc. A ≃10 Mj directly imaged planet is orbiting the star at 9.8 AU (Lagrange et al. 2020). The system is almost edge-on to our line of sight, making β Pictoris b a plausible candidate for the search of THEMs in the IR, through photocenter astrometry of the combined planet and moon (Agol 2015) or by looking for primary and secondary transits of the exomoon.

 

Methods

We scale up a Galilean satellite system around β Pictoris b in order to investigate which properties make a putative exomoon detectable. We use orbital-thermal coupled models that assume a layered, radially symmetric moon, consisting of a silicate mantle and a liquid core. We assume that heat is transferred via melt advection (Moore 2003) and mantle convection from the interior to the surface and we obtain equilibrium temperatures. We explore the parameter space of orbital and physical properties of an exomoon around β Pictoris b by using different rheological models (Maxwell, Andrade).

 

Results

Given a semi-major axis and eccentricity for an 8MIo mass exomoon, we obtain the corresponding interior structure and heat flow through the moon, resulting in a calculated effective temperature at the surface. We present our results for our Andrade rheology model and heat transfer mechanisms (Figure 1) and place constraints on the feasible interior models and orbital parameters for a putative surface heat flux of an exomoon around β Pictoris b. At Io’s orbital eccentricity a 2RIo exomoon would need to be close to the Roche radius of β Pictoris b to reach 600 K and be observed with the JWST (Figure 2), however this limit relaxes for higher eccentricities and bigger moons. We find that the Andrade rheology results in higher surface temperatures when compared to the basic Maxwell viscoelastic model.

Figure 1: Equilibrium surface temperatures of a 2RIo exomoon (Super-Io) around β Pictoris b using Andrade rheology and melt advection. The horizontal line shows Io’s orbital eccentricity.

 

Figure 2: Fluxes at the β Pictoris system. The grey continuous line shows the modeled spectrum of a planet with similar parameters as β Pictoris b (Morley et al. 2015), the dashed black line the blackbody curve of the star and the purple line the one of a Super-Io (2RIo). The horizontal lines are the 5σ and 10,000s integration time detection limits of MIRI/JWST for various bands (Glasse 2010)).

 

References

Agol et al. (2015) The Astrophysical Journal, 812(1), p.5.

Glasse (2010) SPIE, 7731, 77310K.

Lagrange et al. (2020) Astronomy & Astrophysics, 642, p.A18.

Moore  (2003) Journal of Geophysical Research, 108(E8).

Morley et al. (2015) The Astrophysical Journal, 815(2), p.110.

Oza et al. (2019) The Astrophysical Journal, 885(2), p.168.

Peters and Turner (2013) The Astrophysical Journal, 769(2), p.98.

 

How to cite: Kleisioti, E., Dirkx, D., Rovira-Navarro, M., and Kenworthy, M.: Could we observe exomoons around β Pictoris b?, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-546, https://doi.org/10.5194/epsc2021-546, 2021.

EPSC2021-90
Heike Rauer, Isabella Pagano, Miguel Mas-Hesse, Conny Aerts, Magali Deleuil, Laurent Gizon, Marie-Jo Goupil, Ana María Heras, Giampaolo Piotto, Don Pollacco, Roberto Ragazzoni, Gavin Ramsay, and Stéphane Udry

PLATO is an ESA mission dedicated to the study of exoplanets and stars, with a planned launch date in 2026. By performing photometric monitoring of about 250 000 bright stars (mV < 13), PLATO will be able to discover and characterise hundreds of exoplanets, including small planets orbiting up to the habitable zone of solar-like stars. PLATO’s precision will also allow for a precise characterisation of the host stars through asteroseismology. These objectives require both a wide field of view and high sensitivity, which are achieved with a payload comprising 24 cameras with partially overlapping fields of view. They are complemented by 2 more cameras optimised for brighter stars that will also be used as fine guidance sensor. The PLATO development phase started after the mission adoption in July 2017. The Mission Preliminary Design Review (PDR) was declared successful in October 2020. The implementation and delivery to ESA of the flight model CCDs for all cameras (4 CCDs per camera) has been completed. Currently the Structural Thermal Model (STM) of the payload optical bench is being manufactured, while the STM of a single camera has already been successfully tested. In parallel, a first engineering model of a complete, fully functional camera is being integrated, to verify its performance under operational conditions, and the qualification models of the different payload units are being built.

We will present the status of the PLATO payload implementation in the context of the satellite development. In particular, we will describe the payload manufacturing, integration, and tests that will be reviewed at the Critical Milestone in the second half of 2021. We will also summarise the progress made in the science preparation activities, as well as on the ground segment.

How to cite: Rauer, H., Pagano, I., Mas-Hesse, M., Aerts, C., Deleuil, M., Gizon, L., Goupil, M.-J., Heras, A. M., Piotto, G., Pollacco, D., Ragazzoni, R., Ramsay, G., and Udry, S.: The PLATO mission: Overview and status, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-90, https://doi.org/10.5194/epsc2021-90, 2021.

EPSC2021-610
Theresa Lueftinger, Giovanna Tinetti, Paul Ecclestone, Jean-Christophe Salvignol, Salma Fahmy, Pierre-Olivier Lagage, Guisi Micela, Enric Pallé, Olja Panic, Enzo Pascale, Bart Vandenbussche, and Olivia Venot

Ariel, the atmospheric remote-sensing infrared exoplanet large-survey, is the recently adopted M4 mission within the Cosmic Vision science programme of ESA. The goal of Ariel is to investigate the atmospheres of planets orbiting distant stars in order to address the fundamental questions on how planetary systems form and evolve and to investigate in unprecedented detail the composition of a large number of exoplanetary atmospheres. During its 4-year mission, Ariel will observe hundreds of exoplanets ranging from Jupiter- and Neptune-size down to super-Earth size, in a wide variety of environments, in the visible and the infrared. The main focus of the mission will be on warm and hot planets in orbits close to their star. Some of the planets may be in the habitable zones of their stars, however. The analysis of Ariel spectra and photometric data will allow to extract the chemical fingerprints of gases and condensates in the planets’ atmospheres, including the elemental composition for the most favourable targets. The Ariel mission has been developed by a consortium of more than 60 institutes from 15 ESA member state countries, including UK, France, Italy, Poland, Spain, the Netherlands, Belgium, Austria, Denmark, Ireland, Hungary, Sweden, Czech Republic, Germany, Portugal, with an additional contribution from NASA. In this talk, we will review the science goals of the mission and give insight into the current status, both from the ESA and the Ariel Mission Consortium point of view.  

How to cite: Lueftinger, T., Tinetti, G., Ecclestone, P., Salvignol, J.-C., Fahmy, S., Lagage, P.-O., Micela, G., Pallé, E., Panic, O., Pascale, E., Vandenbussche, B., and Venot, O.: Ariel - The ESA M4 Space Mission to Focus on the Nature Of Exoplanets, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-610, https://doi.org/10.5194/epsc2021-610, 2021.

EPSC2021-182
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ECP
Lorenzo V. Mugnai, Enzo Pascale, Billy Edwards, Andreas Papageorgiou, and Subhajit Sarkar

Since the very early phases of designing and developing space instruments, we need fast and reliable tools to validate and optimise the projects. In the framework of the Ariel Space Mission, we developed novel, versatile tools to estimate space instruments performance. 

ExoSim, a transiting exoplanet observation simulator, is a time domain simulator for space telescopes, that has been developed inside the Ariel framework, but already adapted to both HST and JWST, proving its versatility and its capability to accurately predict science products. It can be used to develop the data reduction pipeline, and to optimise systematics removal techniques.

ArielRad, the Ariel radiometric model, is a simulator able to accurately predict the telescope performance in observing a candidate target for all the mission photometric and spectroscopic channels. The software inputs are a target description and a parameterization of the payload, allowing the investigation of different design performance. The software is also able to simulate entire target lists, predicting the observing time and the resulting SNR vs wavelength. Analysing 1000 candidate targets in a 20 minutes time scale, it allows the validation of different observational strategies. The software architecture is based on ExoRad 2, that is publicly available and can be easily adapted to perform the same tasks for other future space missions.

How to cite: Mugnai, L. V., Pascale, E., Edwards, B., Papageorgiou, A., and Sarkar, S.: Performance simulations tools for Space Telescopes applied to Ariel space mission., Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-182, https://doi.org/10.5194/epsc2021-182, 2021.

EPSC2021-185
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ECP
Lorenzo V. Mugnai, Ahmed Al-Refaie, Andrea Bocchieri, Quentin Changeat, Enzo Pascale, and Giovanna Tinetti

In the next decade, the Ariel Space Telescope will provide the first statistical data set of exoplanet spectra, performing spectroscopic observations of about 1000 exoplanets in the wavelength range 0.5 - 7.8 micron during its Reconnaissance Survey. The Ariel Reconnaissance Survey has been designed specifically to identify planets without molecular features in their atmosphere, and select targets (about 500) for accurate chemical characterisation with higher SNR spectroscopic observations.

In this work, we investigate the information content of Ariel's Reconnaissance Survey low resolution transmission spectra. We produce different planetary populations using the Ariel candidate target list, randomizing the planetary atmospheres, and simulating the Ariel observations using the Alfnoor software. Then we analyse the dataset, getting three different results:

(1) We present a solid strategy that will allow selecting candidate planets to be reobserved in an Ariel's higher resolution, using a chi-squared based metric to identify the flat spectra.

(2) Because the reconnaissance survey is not optimised for spectral retrieval, we propose a novel model-independent metric to preliminary classify exoplanets by their atmospheric composition. Without any other planetary information than the spectrum, our metric proves capable of indicating the presence of a molecule when its abundance in the atmosphere is in excess of 10-4 in mixing ratio.

(3) We introduce the possibility of finding other methods to better exploit the data scientific content. We report as an example of possible strategies, a preliminary study involving Deep and Machine Learning algorithms. We show that their performance in identifying the presence of a certain molecule in the spectra is marginally better than our metric for some of these algorithms, while others outperform the metric. 

We conclude that the the Ariel reconnaissance survey is effective in detecting exoplanets manifesting featureless spectra, and we further show that the data collected in this observing mode have a rich scientific content, allowing for a first chemical classification of the observed targets.

How to cite: Mugnai, L. V., Al-Refaie, A., Bocchieri, A., Changeat, Q., Pascale, E., and Tinetti, G.: Alfnoor: a population study on Ariel's low resolution transmission spectra., Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-185, https://doi.org/10.5194/epsc2021-185, 2021.

EPSC2021-241
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ECP
Andrea Bocchieri and Enzo Pascale

Ariel, the Atmospheric Remote-sensing Infrared Exoplanet Large-survey, is a medium-class space mission part of ESA's Cosmic Vision programme, due for launch in 2029. Ariel will survey a diverse sample of about 1000 extrasolar planets in the visible and infrared spectrum to answer questions about their composition, formation and evolution. Ariel mounts an off-axis Cassegrain telescope with an 1100 mm x 730 mm elliptical mirror and has two separate instruments (FGS and AIRS) that cover the 0.5-7.8 micron spectral range. To study the Ariel optical performance and related systematics, we developed PAOS, the Physical Ariel Optics Simulator, an End-to-End physical optics propagation model of the Ariel Telescope and subsystems. PAOS is a Python code that consists of a series of functions and procedures that reproduces the Ariel optical design. Using PAOS, we can investigate how diffraction affects the electromagnetic wavefront as it travels through the Ariel optical systems and the resulting PSFs in the photometric and spectroscopic channels of the mission. This enables to perform a large number of detailed analyses, both on the instrument side and on the optimisation of the Ariel mission. In particular, PAOS can be used to support the requirement on the maximum amplitude of the aberrations for the manufacturing of the Ariel primary mirror, as well as to develop strategies for in-flight calibration, e.g. focussing procedures for the FGS and AIRS focal planes, and to tackle systematics such as pointing jitter and vignetting. With the Ariel mission now in the process of finalizing the instrument design and the data analysis techniques, PAOS will greatly contribute in evaluating the Ariel payload performance with models to be included in the existing Ariel simulators such as ArielRad, the Ariel Radiometric model, and ExoSim, the Exoplanet Observation simulator, for the purpose of studying and optimising the science return from Ariel.

How to cite: Bocchieri, A. and Pascale, E.: PAOS, the Physical Optics Propagation model of the Ariel optical system, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-241, https://doi.org/10.5194/epsc2021-241, 2021.

EPSC2021-421
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ECP
Robert Zellem

After JWST, NASA’s next flagship astrophysics mission is the ambitious Nancy Grace Roman Space Telescope. Roman will include the Coronagraph Instrument (CGI) will be the first high-performance stellar coronagraph using active wavefront control for deep starlight suppression in space, providing unprecedented levels of contrast, spatial resolution, and sensitivity for astronomical observations in the optical. During its Technology Demonstration phase, CGI will resolve the signal of an exoplanet via photometry and spectroscopy and directly image and measure the polarization of disks. Future flagship mission concepts (e.g., HabEx and LUVOIR) aim to characterize Earth analogues with visible light flux ratios of ~10-10, and CGI is a critical intermediate step toward that goal, with predicted capability of ~10-9. Here, we present CGI’s design and capability as well as some anticipated results from its technology demonstration.

How to cite: Zellem, R.: Overview of the Nancy Grace Roman Space Telescope Coronagraph Instrument and Its Technology Demonstration, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-421, https://doi.org/10.5194/epsc2021-421, 2021.

EPSC2021-298
Jean-Philippe Beaulieu and Etienne Bachelet

As the Kepler mission has done for hot exoplanets, the ESA Euclid and NASA Roman missions have the potential to create a breakthrough in our understanding of the demographics of cool exoplanets, including planets on very wide orbits, unbound, or "free-floating", planets (FFPs). Current ground-based microlensing observations have provided preliminary evidence for a potentially significant population of Super-Earth FFPs. Roman will dedicate part of its core survey program to the detection of cool exoplanets via microlensing, while Euclid may undertake a microlensing program as an ancillary science goal. We argue that simultaneous observations of short-duration microlensing events by Roman and Euclid will enable not just the verification of FFPs, but also a direct measurement of their masses, distances and transverse motions, via the detection of microlens parallax between Euclid and Roman. We use simulations of the joint-mission detection capabilities to show that parallax detections will be possible down to Earth-mass FFPs. The mass and phase-space measurements from a joint survey could thus provide strong clues to the primary mode of FFP formation.

We also demonstrate that an early brief Euclid survey (∼5 h) of the Roman fields shortly after the Euclid launch would be also very valuable. It would allow the measurement of at least 10% of the events’  relative proper motions and 35% of the lens magnitudes very early on the life of the Roman Survey. We further discuss additional valuable science that will be facilitated by a joint Roman-Euclid microlensing campaign.

How to cite: Beaulieu, J.-P. and Bachelet, E.: Microlensing survey combining  Roman and Euclid Space Telescopes, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-298, https://doi.org/10.5194/epsc2021-298, 2021.

EPSC2021-772
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ECP
Óscar Carrión-González, Antonio García Muñoz, Nuno C. Santos, Juan Cabrera, Szilárd Csizmadia, and Heike Rauer

Abstract

The coronagraph instrument aboard the Nancy Grace Roman Space Telescope is a technology demonstrator that will perform the first reflected-starlight direct imaging observations of exoplanets. This instrument will pave the way for future missions such as LUVOIR or HabEx, which have the goal of characterizing the atmospheres of Earth-like exoplanets. In this work we develop a statistical method to compute which of the confirmed exoplanets in the NASA Exoplanet Archive would be accessible in reflected starlight to a direct-imaging telescope. By applying our method to the Roman Telescope’s coronagraph, we show that an eventual science phase of the Roman Telescope’s coronagraph has a remarkable potential to study cold and temperate exoplanets and initiate their atmospheric characterization.

 

Introduction

The years until the expected launch of the Roman Telescope[1] in 2025 should be used to improve the orbital characterization of the most interesting targets through radial velocity or astrometry campaigns. For this, a target list of known exoplanets that could be observed with the Roman Telescope’s coronagraph is needed. Additional figures describing the detectability and scientific interest of each accessible exoplanet are useful to prioritize the observations of the targets.

 

Statistical method

We use the NASA Exoplanet Archive[2] as the main source of information for the planetary and stellar properties of each of the about 4300 confirmed exoplanets. For each exoplanet, we compute 10,000 orbital realizations letting each of the parameters involved vary within its reported upper and lower uncertainties. When the orbital inclination (i), the eccentricity (e) or the argument of periastron of the planet (ωp) are unconstrained, we randomly draw their value at each orbital realization from uniform distributions. When the planet radius is unknown, we compute it by means of published mass-radius relationships[3][4]. By discretizing each orbital realization into 360 positions, we compute at each position the angular separation between the planet and the star (Δθ) and the planet-to-star contrast ratio (Fp/F*). We define a planet as Roman-accessible if at a certain orbital position its angular separation is within the inner and the outer working angles (IWA, OWA) of the coronagraph and, additionally, the planet-to-star contrast is brighter than the minimum contrast (Cmin) that the coronagraph can detect.

Our main outputs are the probability of a planet to be Roman-accessible (Paccess), the range of observable phase angles (αobs), the number of days per orbit in which the planet is accessible (tobs) and its transit probability. Due to its interest for atmospheric modelling, we also compute the equilibrium temperature (Teq) at each orbital position. This allows us to compute the mean value of Teq throughout the orbit, its variation due to orbital eccentricity and the variation of Teq that takes place while the planet is accessible, which could result in detectable atmospheric variability.

With this method, we computed the accessibility of each planet at wavelengths 575, 730 and 825 nm, consistent with the coronagraph filters that are currently commissioned. We repeated this study for three plausible configurations of the coronagraph because its final design is not yet completed. We label these configurations as optimistic (IWA=3λ/D, OWA=9λ/D, Cmin=1×10−9), intermediate (IWA=3.5λ/D, OWA=8.5λ/D, Cmin=3×10−9) and pessimistic (IWA=4λ/D, OWA=8λ/D, Cmin=5×10−9).

 

Results

We find up to 26 exoplanets Roman-accessible exoplanets in the optimistic scenario with Paccess>25% and orbiting stars brighter than V=7 mag[5]. We apply the latter two vetting criteria throughout our work due to the particular constraints of the Roman Telescope mission timeline and the sensitivity of its coronagraph instrument. This number of Roman-accessible exoplanets is reduced to 10 and 3 in the intermediate and pessimistic scenarios, respectively.

For the Roman-accessible exoplanets in the optimistic scenario we carried out a population study and found that this set of planets is dominated by giant exoplanets more massive than Jupiter. Interestingly, it also includes the low-mass planets tau Cet e and f, which orbit near the habitable zone of their host star. These two planets are however barely accessible in the intermediate or pessimistic coronagraph scenarios (Fig. 1). Thirteen of the 26 Roman-accessible exoplanets are part of multi-planet systems and three of them have inner companions observed in transit, which would enable the simultaneous characterization of the inner and the outer regions of these planetary systems. The mean equilibrium temperatures of the Roman-accessible planets range from values in the order of that of Uranus to values above 400 K, including some targets at ~300 K (Fig. 2).

For a selection of particularly interesting targets, we analysed in more detail the prospects for observing and eventually characterizing these planets. For instance, we discussed how the detectability prospects may change if additional constraints on the orbital inclination are set e.g. with astrometry (Fig. 1).

We find some exoplanets with remarkably wide ranges of observable phase angles, which makes them interesting for atmospheric characterization with reflected-starlight phase curves[6]. In this regard, we also discussed the importance of consistently reporting the planet and stellar parameters in exoplanet catalogues such as the NASA Archive and the misleading detectability results that might be achieved if an A standardization process is not performed.

Overall, we find that a science phase of the Roman Telescope’s coronagraph would have an extraordinary potential to perform one-of-a-kind observations before next-generation missions that are not expected at least until the mid-2030s.

 

References

[1] Spergel et al. (2013), https://arxiv.org/abs/1305.5422
[2] Akeson et al.
(2013), PASP, 125, 989
[3] Hatzes & Rauer (2015), ApJL, 810, L25
[4] Otegi et al. (2020), A&A, 634, A43
[5] Carrión-González et al. (2021), A&A accepted
[
6] Carrión-González et al. (2021), in prep.

How to cite: Carrión-González, Ó., García Muñoz, A., Santos, N. C., Cabrera, J., Csizmadia, S., and Rauer, H.: A catalogue of up to 26 known exoplanets accessible to reflected-starlight observations with the Roman Space Telescope, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-772, https://doi.org/10.5194/epsc2021-772, 2021.

EPSC2021-284
Daniel Angerhausen and Sascha Quanz and the LIFE collaboration

Summary

The Large Interferometer For Exoplanets (LIFE) mission concept is a project initiated in Europe with the goal to consolidate various efforts and define a road map that eventually leads to the launch of a large, space-based mid-infrared (MIR) nulling interferometer observatory. This mission will be able to investigate the atmospheric properties of a large sample of  terrestrial, potentially habitable exoplanets. In this contribution we present a status report and summarize new results from the LIFE Mission initiative. 

Context

One of the major goals of exoplanetary science and possibly the most challenging question in 21st century exoplanet research is the investigation of the atmospheric properties for a large number (~100) of terrestrial exoplanets. This is only partially driven by the idea to search for habitable conditions and identify potential biosignatures, since such a statistically significant data-set is - in a more general sense - invaluable for understanding the diversity of planetary bodies. First steps in this direction will be taken in the coming 10-15 years with funded or selected ground- and space-based projects and missions. And while exoplanet science is omnipresent on the road maps of all major space agencies, none of them will be able to deliver such a comprehensive and consistent, big data set. An alternative to the mainly discussed large space-based coronographic missions or the starshade concept is to separate the light emitted by the planet from that of its host star by means of an interferometer.
In this contribution we summarize new results from the LIFE Mission initiative, which addresses this issue by investigating the scientific potential and technological challenges of an ambitious mission employing a formation-flying nulling interferometer in space working at mid-infrared wavelengths [1,2,3]. Centered around clear and ambitious scientific objectives the project will define the relevant science and technical requirements. The status of key technologies will be re-assessed and further technology development will be coordinated. LIFE is based on the heritage of ESA/Darwin and NASA/TPF-I, but significant advances in our understanding of exoplanets and newly available technologies will be taken into account in the LIFE mission concept. Advances in our knowledge of the exoplanet population as well as significant progress in relevant technologies justify the need, but also the feasibility for a future mission like LIFE to investigate one of the most fundamental questions of mankind: How unique is the phenomenon we call life in the universe?