EXOA9

During last decade there have been a tremendous increase in detection and characterization of low-mass exoplanets, reaching the Earth size and mass domain, in particular those orbiting M dwarf stars, due to their smaller sizes and masses, resulting in planet larger transit amplitude and radial velocity signals. Extremely precise instruments such as the ESPRESSO spectrograph are designed to detect Earth-like planets, requiring in addition a detailed modeling of the stellar activity.

ESPRESSO is an ultra-stable high-resolution spectrograph, designed and developed involving institutions from Switzerland, Italy, Portugal, Spain, and ESO, which is located in the combined Coudé Lab of the VLT at ESO, and is able to operate either using one 8.2m-VLT UT or simultaneously with the four VLT UTs. ESPRESSO started routine operations in October 2018 at ESO, and is designed to achieve a radial velocity precision of 10 cm/s, thus opening the possibility to explore new frontiers in science such as the search for rocky planets and the measurement of the variation of physical constants (Pepe et al. 2021). ESPRESSO is considered a precursor of the ultra-stable high-resolution spectrograph ANDES (formerly known as HIRES) for the 39m-ELT telescope (Marconi et al. 2021).

ESPRESSO has been very successful so far in detecting and characterizing low-mass planets demonstrating the sub-m/s capabilities of the instrument, providing a unique ground-based facility with great synergy with exoplanet dedicated satellites such as Kepler (Toledo Padrón et al. 2020), TESS (Demangeon et al. 2021) and CHEOPS (Leleu et al. 2021). One of the most relevant recent achievement of ESPRESSO is the confirmation of the 11.2d Earth mass planet Proxima b in the habitable zone of Proxima Centauri, previously reported in Anglada-Escudé et al. (2016), and the discovery of the sub-Earth mass planet Proxima d in  a 5.1d orbit with a semiamplitude velocity of 40 cm/s together with a simultaneous, precise characterization of the activity of the star (Suárez Mascareño et al. 2020; Faria et al. 2022). This discovery together with the 5yr period super-Earth planet candidate Proxima c reported in Damasso et al. (2020) composes the currently known planetary system in the nearest stellar neighbour to our Sun, encouraging new detail studies of this star with current and future facilities such as ANDES@ELT. In this talk I will briefly summarize the main features of ESPRESSO performance focusing on revealing the planetary system around Proxima Centauri and future prospects.

How to cite: González Hernández, J. I. and the ESPRESSO consortium: The planetary system of Proxima Centauri seen with ESPRESSO, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1214, https://doi.org/10.5194/epsc2022-1214, 2022.

After the detection of numerous planetary systems outside of our own Solar System which tend to be extremely diverse and which show a wide range of evolutionary states, the focus is now shifting to a characterization of their formation and evolution, as well as to the architecture of planetary systems and planet habitability.

One of the astonishing discoveries in exoplanet research has been the detection of Jupiter-like planets (in size and mass) that orbit their host star within 10 days. These so-called hot Jupiters are rarely accompanied by smaller close-in companions. TOI-1130 is one of very these rare systems. It hosts two transiting planets: a hot Jupiter and an inner low-mass planet that are near to the 2:1 period commensurability.

Planetary systems with transiting planets are markedly well-suited for a detailed characterization, since they allow the measurement of the planetary radius, which is essential to constrain the planet’s evolution and migration history, as well as to characterize the internal structure of the planet. The second fundamental parameter for the characterization is the planetary mass, that together with the radius allows the bulk density of a planet to be estimated, thereby constraining its composition.

In order to find out the history and future evolution of exoplanet systems, a complete knowledge of all orbital and planetary parameters with a high accuracy is crucial. However, precise measurements of the planetary mass are difficult to obtain, in particular for small planets. If there are multiple planets in a system close to a period commensurability, as is the case for TOI-1130, the planetary masses can be determined using the gravitational interactions leading to measurable transit timing variations.

TOI-1130 is a known planetary system consisting of a hot Jupiter, TOI-1130 c, on an 8.4-day orbit accompanied by an inner Neptune-sized planet, TOI-1130 b, with an orbital period of 4.1 days around a K-dwarf. As part of the ongoing radial velocity (RV) follow-up program carried out by our team with the HARPS spectrograph, we collected precise radial velocity measurements of TOI-1130. We perform a photodynamical modeling of the RVs, and the transit photometry from the Transiting Exoplanet Survey Satellite (TESS) and the TESS Follow-up Observing Program. We find that the two planets orbit with small eccentricities in a 2:1 resonant configuration. This is the first system where a hot Jupiter accompanied by an inner lower mass planet is locked in a mean-motion-resonance. We discuss possible formation scenarios.

How to cite: Korth, J. and the KESPRINT team, TESS, and TFOP: Not alone in solitude: a look into the surprising world of TOI-1130, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-14, https://doi.org/10.5194/epsc2022-14, 2022.

Super-Neptunes straddle between ice and gas giants, with masses between that of Neptune and Saturn, and their study can contribute to a better understanding  of exoplanetary systems' formation and evolution. Here we present a new transiting super-Neptune discovered by the WASP-South [1] transit survey, WASP-193b (K. Barkaoui et al. Submitted in Nature Astronomy). Photometric follow-up was performed by the TRAPPIST-South [2] and SPECULOOS-South telescopes [3] (right panel in Fig. 1) and spectroscopic measurements were collected by the HARPS [4] and CORALIE [5] spectrographs (bottom left in Fig. 1). We performed a joint analysis of the light curves and radial velocity time series using the MCMC [6] algorithm to constrain the system's physical properties. WASP-193b completes an orbit around its F9V-type host star every 6.25d. Its mass is 0.14 ± 0.03M_Jupiter (i.e. 2.6 M_Neptune) and its radius is 1.46 ± 0.06 R_Jupiter, which translates into an ultra-low density of 0.060 ± 0.014 g cm^-3 (Fig. 2).
Its huge radius cannot be reproduced by standard models of irradiated gas giants [7], even when assuming a coreless structure. A mechanism of energy deposit into its interior (e.g. Ohmic dissipation or tidal heating) has to be advocated to explain its bloated state. Its high equilibrium temperature (T_eq = 1254 ± 31 K), combined with its super-low density and the infrared brightness (J_magnitude = 10.95) of its host star, make WASP-193b an exquisite target for a thorough atmospheric characterization with HST and JWST. The measurement of its orbital obliquity could also inform us of its dynamical history [9], shedding light on its energy budget evolution.

Fig. 1: Top left panel: Detrended discovery  light-curve of WASP-193 obtained with WASP-South (gray points: unbinned and black points: bin width = 30min), period-folded using the orbital period  deduced from our data analysis. Right panel: Follow-up transit photometry of WASP-193b. Four transits observed by TRAPPIST-South and one  by SPECULOOS-South, period-folded using the best-fitting transit ephemeris deduced from our global MCMC analysis. Each individual transit light curve has been corrected by the baseline model. The coloured points are data binned to 7.2min and the best-fitting model is superimposed in red. Right panels: Residuals from the fits for each transit light curve. Bottom left panel: RVs obtained with the CORALIE (blue) and HARPS (red) spectrographs for WASP-193 period-folded using the best-fitting orbital model is superimposed as a  solid line (in m s^-1).

Table. 1: The WASP-193 system parameters derived from our global MCMC analysis (medians and 1σ limits of the marginalized posterior probability distributions).

Fig. 2: Mass--density diagram of known transiting exoplanets from NASA Archive of Exoplanets. The size of the points scales with the planetary radius. The points are coloured according to their Transmission Spectroscopy Metric (TSM, [9]).  WASP-193b is shown with its corresponding error bars. We highlighted also least dense planets known to date are labelled: Kepler-51b, Kepler-51c, Kepler-51d [10] and HAT-P-67b [11]. Giant planets of the Solar System are also shown.

References
[1] Pollacco, D. L., et al. 2006, PASP, 118, 1407
[2] Gillon, M., et al. 2011, EPJ Web of Conferences, 11, 06002
[3] Jehin, E., et al. 2018, The Messenger, 174, 2
[4] Francesco, P., et al. 2000, Proc. SPIE Vol. 4008, p. 582-592
[5] Queloz, D., et al. 2000, Springer-Verlag, p. 548
[6] Gillon, M., et al. 2012, , 542, A4
[7] Fortney, J. J., et al. 2007, , 659, 1661
[8] Triaud, A. H. M. J., et al. 2010, , 524, A25
[9] Kempton, E. M. R., et al. 2018, PASP, 130, 114401
[10] Masuda, K. 2014, , 783, 53
[11] Zhou, G., et al. 2017, , 153, 211

How to cite: Barkaoui, K., Pozuelos, F. J., Gillon, M., Coel, H., and teams, W. T. S. H. A. C.: WASP-193b: An extremely low-density super-Neptune, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-709, https://doi.org/10.5194/epsc2022-709, 2022.

In the age of JWST, temperate terrestrial exoplanets transiting nearby late-type M dwarfs provide unique opportunities for characterizing their atmospheres, as well as searching for biosignature gases. In this context, the benchmark TRAPPIST-1 planetary system has garnered the interest of a broad scientific community.

The SPECULOOS (Search for habitable Planets EClipsing ULtra-cOOl Stars) project, an exoplanet transit survey targeting a volume-limited (40 pc) sample of about 1700 late-type (M6 and later) dwarfs using a network of 1m-class robotic telescopes, began its scientific operations three years ago. In this talk, I will present an update on the current status of the survey and an overview of recent results.

In particular, I will describe how an efficient synergy with the TESS mission and other ground-based facilities led to the exciting new discovery of two temperate super-Earths transiting a nearby M6 dwarf, with the outer one orbiting in the habitable zone. In terms of potential for atmospheric characterization, we estimate that this planet is the second-most favorable habitable-zone terrestrial planet found so far after the TRAPPIST-1 planets. The discovery of this remarkable system offers another rare opportunity to study temperate terrestrial planets around our smallest and coolest neighbours.

How to cite: Delrez, L. and the SPECULOOS team: An update on the SPECULOOS project and new results, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-529, https://doi.org/10.5194/epsc2022-529, 2022.

The composition of several exoplanet atmospheres has been largely debated with contrasting results in the literature. Low- and high-resolution spectroscopy offer complementary views, although sometimes appear to be in sparkling contrast. We present a new approach to simultaneously model low- and high-resolution observation and apply this method to resolve known controversies in the literature. We show that the synergy between different techniques of observations is significantly more informative than the separate analyses. We recommend the joint analysis of low- and high-resolution exoplanet spectra to fully exploit the potential of upcoming space missions, such as JWST, Twinkle and Ariel.

How to cite: Morello, G., Pallé, E., Orell-Miquel, J., Masseron, T., and Esparza-Borges, E.: Synergies between low- and high-resolution spectroscopy of exoplanet atmospheres, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1233, https://doi.org/10.5194/epsc2022-1233, 2022.

With the swift advance in exoplanet sciences it is now possible to characterize not only the fundamental parameters (mass and radius) of planets but also their interior structure and bulk composition. The former is known to influence on the habitability conditions of terrestrial planets, and the latter in itself is a key aspect to understand planet formation processes and the origin of their diversity.

In order to accurately assess planetary internal composition, the derivation of the chemical abundances of the host stars is of extreme importance. In particualr, stellar abundances of Fe, Si, Mg are proposed as principal constraints to reduce degeneracy in exoplanet interior structure models under assumption of identical composition of these elements in the rocky planets and their host stars.

This regularly used assumption is based on our knowledge that stars and planets form from the same primordial gas and dust cloud. It is also supported by our Solar System observations for which we know that the composition of major rock forming elements (such as Mg, Si, and Fe) in the meteorites and telluric planets (with the exception of Mercury) is similar to that of the Sun. However, direct observational evidence for the aforementioned assumption for exoplanets is absent.

By using the largest possible sample of precisely characterized low-mass planets and their host stars, we show that the composition of the planet building blocks indeed correlates with the properties of the rocky planets (see Fig. 1). We also find that on average the iron-mass fraction of planets is higher than that of the primordial values, owing to the disk-chemistry and planet formation processes. Additionally, we show that super-Earths and super-Mercuries appear to be distinct populations with differing compositions, implying differences in their formation processes. We suggest that giant impact alone is not responsible for the high-densities of super-Mercuries.

I propose an oral contribution to speak about these very recent results published in Scinece.

Fig. 1 The iron-mass fraction of the planets inferred from the planets' mass and radius as a function of the iron-mass fraction of the protoplanetary disk, estimated from the host star abundances. Super-Mercuries (in brown) and super-Earths (in blue) appear as two distinct groups.

How to cite: Adibekyan, V., Dorn, C., Sousa, S., Santos, N., Bitsch, B., Israelian, G., Mordasini, C., Barros, S., Delgado Mena, E., Demangeon, O., Faria, J., Figueira, P., Hakobyan, A., Osagh, M., Soares, B., Kunitomo, M., Takeda, Y., Jofré, E., Petrucc, R., and Martioli, E.: Diversity of terrestrial planets: a link to the chemical makeup of their host stars, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-74, https://doi.org/10.5194/epsc2022-74, 2022.

Planets smaller than Neptune are ubiquitous in the Galaxy and those around M stars constitute the bulk of warm and temperate worlds amenable for detailed atmospheric characterization. In this talk, we present a re-analysis of all the available data on small transiting planets around M dwarfs, refining their masses and radii (Luque & Pallé 2022, in press). Our precisely characterized sample reveals that this population is well described by only three discrete planet density populations, with bulk densities centered at 1.0, 0.5 and 0.24 relatively to Earth's. The first are rocky planets, the second are water worlds, and the third are puffy planets with Neptune-like densities. This density classification offers a much better insight to disentangle planet formation and evolution mechanisms, which are degenerate when using a radius-based classification. Our results are at odds with atmospheric mass loss models aiming to explain the bimodal radius distribution and suggest that the gap separates dry from water worlds rather than rocky planets with or without H/He envelopes. Formation models including type I migration explain naturally the observations independently of the accretion mechanism: rocky planets form within the snow line, water worlds form beyond and later migrate inwards. These results are to be published in Science and are currently under embargo.

How to cite: Luque, R. and Pallé, E.: On the nature of small planets orbiting low-mass stars, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-89, https://doi.org/10.5194/epsc2022-89, 2022.

Even though our understanding of giant planet formation and evolution mechanisms has significantly improved over the past twenty years, the impact of the host star’s properties (mass, temperature, age, and metallicity) on the giant planet distribution remains to be thoroughly studied. The timescales and occurrences of the different planet formation scenarios have to be assessed, quantified, and compared. To that extent, detecting hot Jupiters and brown dwarfs orbiting hot stars is essential if we want to constrain giant planet and brown dwarf formation models across various stellar types and the impact of stellar mass (e.g., core-accretion models predict an increase in gas giant frequency with stellar mass). However, obtaining mass measurements of planets orbiting stars hotter than the Kraft break (6200 K) is inherently more difficult than for Solar-type stars. These stars have thin convective envelopes and do not efficiently generate magnetic winds. As a result, they remain rapidly rotating and due to their high temperature they exhibit fewer spectral lines. Their high rotation velocities lead to a substantial broadening of their observed spectral lines, making RV measurements of hot stars difficult. In addition, stellar activity and pulsations can induce RV variations that can mask or even mimic the RV signature of orbiting exoplanets. In particular, only 20% (99 exoplanets) of transiting exoplanets with precise densities have been detected to orbit AF-type stars with T_eff > 6200 K (< F8V). Figure 1 summarizes the scarcity of planets detected around host stars with different stellar types. The vertical line at 6200 K indicates the Kraft break where stars retain their high rotational velocities.

We began a radial velocity follow-up survey in January 2021 with the CORALIE spectrograph to obtain mass measurements (and thus densities) of TESS (Transiting Exoplanet Survey Satellite) Objects of Interest (TOIs). The sample consists of 350 TESS giant planet candidates (R > 7 R_⊕) brighter than V = 12 mag. We obtain precise radial velocities with the cross-correlation function (CCF) technique using updated binary masks specifically for hot stars. In this sample we find ~40% are false positives (including stellar binaries), ~20% are planets, and ~4% are brown dwarfs with the remainder yet to be characterised (Figure 2). I will present the statistical findings of our survey and our new detections including three brown dwarf companions, TOI-629b, TOI-1982b, and TOI-2543b, and one massive planet, TOI-1107b (Psaridi et al. 2022, Figure 3). Both TOI-1107b and TOI-1982b present an anomalously inflated radius with respect to the age of these systems. TOI-629 is among the hottest stars with a known transiting brown dwarf. TOI-629b and TOI-1982b are among the most eccentric brown dwarfs. The massive planet and the three brown dwarfs add to the growing population of well-characterized giant planets and brown dwarfs transiting AF-type stars and they reduce the apparent paucity.

Furthermore, we acquired 10 nights on the HARPS spectrograph during P108 to further characterise planet candidates in the Saturn regime transiting fast rotating stars with T_eff > 6550 that require higher precision and efficiency. This program ended in the discovery of several planetary discoveries including TOI-615b, TOI-622b and TOI-2641b (Psaridi et al. in prep), three Saturn-mass planets orbiting stars above the Kraft break (Figure 4).

Figure 1: Number of known exoplanets with precise mass and radius measurements (σ_M/M ≤ 25% and σ_R/R ≤ 8%) as a function of stellar effective temperature. The black vertical line at 6200 K indicates the Kraft break.

Figure 2: Companion radius over stellar effective temperature T_eff diagram for our TESS sample. The red circles display the confirmed false positives (including SB1, SB2, blends etc), the blue circles display the confirmed planets and the black circles diplay the confirmed brown dwarfs. The grey circles display TOIs that have not yet been solved. The size scales inversely with the period of the companion.

Figure 3: Companion mass over stellar effective temperature T_eff diagram for massive planets (M_P > 3 M_Jup) and transiting brown dwarfs shown in blue. The four new companions are shown in yellow. The red circles display confirmed companions detected by TESS. The size scales inversely with the period of the companion. The red, vertical line corresponds to the Kraft break (6200 K) while the horizontal lines correspond to the approximate boundaries of the brown dwarf regime (13 M_Jup) and the transition to high-mass brown dwarfs (42.5 M_Jup). Figure from Psaridi et al. 2022.

Figure 4: RVs from CORALIE (black) and HARPS (orange) with Keplerian model showing the detection of three Saturn-mass planets transiting F-type stars. The errobar in blue displays the photon noise and in red the photon noise plus the stellar jitter.

How to cite: Psaridi, A., Bouchy, F., Lendl, M., and Grieves, N.: Exploring the densities of planets and brown dwarfs transiting hot stars above the Kraft break, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-643, https://doi.org/10.5194/epsc2022-643, 2022.

Our Galaxy is composed of different stellar populations which are characterized by different chemical abundances. They are thought to imprint the composition of small bodies formed together with planets : planet building blocks (PBB), asteroids and interstellar objects.

We investigated the expected PBB composition in different Galactic regions using the ground-based spectroscopic surveys GALAH and APOGEE ; and the stoichiometric condensation model from Bitsch & Battistini (2020). This study has revealed the potential link between the PBB composition and the stellar populations across the Galaxy (Cabral et al, submitted).  

Interestingly, the PBB compositions determined from large observational surveys reveal common trends determined previously with synthetic models. We confirm the PBB composition valley separating the thin disk stars from the thick disk stars (i.e. a bimodal distribution of compositions) already highlighted in our previous study (Cabral et al. 2019) using the Besançon stellar population synthesis model of the Milky Way.

Moreover, we find that metal-poor stars both in the thin and thick disks should host water-rich PBB. Given the importance of water abundance in planet formation simulations (Morbidelli et al. 2015, Ros et al. 2013, 2019), we discuss in a galactic context the potential impact for the early phases of planet formation.

Overall we find that the chemical abundances of host stars should impact the composition of exoplanets, as well as small body populations found around these stars. Our results imply that thick disk stars (which are rather alpha-rich, metal-poor stars) are suitable hosts for ice-rich small bodies (cf. Figure). Whether thick disk stars are suitable for water worlds or/and hycean planets (Madhusudhan et al. 2021) remains matter of debate.

How to cite: Cabral, N., Guilbert-Lepoutre, A., Bitsch, B., and Lagarde, N.: How does the origin of stars in the Milky Way affects the composition of planet building blocks?, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-894, https://doi.org/10.5194/epsc2022-894, 2022.