Resumo:

The existence of a radius valley separating super-Earths from mini-Neptunes, stands as one of the most important observational constraints to understand the origin and composition of exoplanets with radii below Neptune. In this talk, I will first summarise results from combined planet formation-evolution simulations accounting for the origin of the radius valley around solar-type stars (Venturini et al. 2020), and then present new results for a wide range of stellar masses. While a clear radius valley appears for stellar masses larger than 0.4 Msun, for lower stellar masses the valley gets filled by migrating small water-rich planets. Instead, a "density valley" separating rocky from water-rich planets emerges for all stellar types. I will discuss the implications of our formation-evolution models for observations.

Resumo:

During the last three decades, great advances have been made in the field of exoplanets. Among them, the discovery of an extreme class: the hot Jupiters. These exoplanets are objects with size and mass similar to Jupiter, but unlike the gas giant of the Solar System, their orbital period is less than ten days. This makes them extremely irradiated planets and, consequently, with higher temperatures. Since they are so close to their host stars, it is reasonable to assume that there is a direct stellar influence on the atmosphere of these objects. To study some of these effects, we can analyze the parameters obtained from secondary eclipses at infrared bands. These observations may provide important information, such as the brightness temperature and the presence or absence of thermal inversion layer in their atmospheres, when compared to models. Using a sample of 63 hot Jupiters with information on temperature inversion and stellar activity, we analyze the hypothesis that exoplanets without temperature inversion layer orbit active stars, while exoplanets with inversion orbit inactive stars. Furthermore, we reproduce two approaches from previous works that try to classify hot Jupiters according to their brightness temperatures and their relative fluxes. We did not find a clear correlation between the considered brightness temperatures and the stellar chromospheric activity index, except for the H and 5.8 µm bands that showed a weak correlation. In addition, we did not find a clear separation between exoplanets with or without thermal inversion as a function of stellar activity. We verified that the most irradiated exoplanets have atmospheric thermal inversion, while the least irradiated ones do not. Therefore, we conclude that stellar influence must be considered when studying the atmospheres of hot Jupiters. In the future, this research may serve as a basis for studying the atmosphere of rocky exoplanets.

Resumo:

Protoplanetary disks are the sites of planet formation. For this reason their physical properties determine the planet formation process. A correct modelling of protoplanetary disks is, consequently, key to understanding planetary formation. Here we present a disk population synthesis study aimed at reproducing the available observational data of protoplanetary disks. We consider that disks evolve by viscous accretion and internal photoevaporation. The initial conditions, such as the masses and sizes of the discs, follow statistical distributions inferred from observations. We analyze the impact of stellar mass distributions and star formation rates on the time evolution of the fraction of stars with disks, and on the stellar mass accretion rates observed in young stars clusters. We show that, because massive stars dissipate their disks faster, the observed fraction of stars with disks in star-forming regions is dominated by disks around low-mass stars. From our models, we obtain a median disk lifetime of ~4.2 My, showing a very good agreement with observations.

Resumo:

The Solar system stands out from most known planetary systems. Is our system unusual, or is this the result of observational biases? To answer this, a key focus of current research is the search for Jupiter analogues. Detecting Jupiter-like planets helps unravel the uniqueness of the Solar system and sheds light on the formation of systems containing a particular type of gaseous giant: cold Jupiters. We present the discovery of a cold Jupiter in a system alongside a hot Jupiter. We then investigate how changes in observation strategy can influence the ease with which such planets can be detected. By varying cadence and measurement precision, we estimate the additional data required to detect hypothetical cold Jupiters in our target systems. Systems with both hot and cold Jupiters are intriguing. Hot Jupiters are thought to form far from their host star and migrate inward. This migration could be influenced by another giant planet in the system, pulling one planet inward while ejecting the other to a distant, eccentric orbit. To test this hypothesis, it is critical to search for additional planets in those systems. Our work will inform the best observation strategy to perform that search in years and decades to come.

Resumo:

We recently used MAROON-X spectra to confirm the existence of an exoplanet in a wide binary system (projected separation $\sim$11 400 AU). Our results indicate that only one component (TOI 1173 A) hosts an exoplanet, probably a Super-Neptune, with Msini = 26 ME (Earth Masses), R = 9 RE (Earth Radii), P = 7 days, and e = 0.11. The spectroscopic stellar parameters show that the planet-hosting component (TOI 1173 A) is hotter ($\sim$300 K) and higher in iron ($\sim$0.025 dex) than its companion (TO I1173 B). When the differential abundance between both components (TOI 1173 A-B) is plotted against the condensation temperature (TC), a clear abundance pattern is revealed, in which TOI 1173 A is deficient in refractory elements relative to the companion (see the below figure). To our knowledge, this is the first circumprimary exoplanet with a TC trend detected in a very wide binary system. This preliminary finding is aligned with the gas planet formation scenario (e.g., Huhn $\And$ Bitsch 2023, Booth $\And$ Owen 2020), which suggests that the formation of a gas planet opens a gap in the gas disk, causing refractory elements to be trapped outside its orbit in pressure traps. Additionally, in this work, we will also discuss the various scenarios from planet formation to planet engulfment to explain the different abundance patterns observed in our new sample of 70 wide binaries discovered with Gaia and TESS data.

Resumo:

On Mars there is no ozone layer to protect the surface, because the O2 levels are very low, therefore, UV radiation of wavelength between 200 and 300 nm manages to penetrate the Martian soil. The solar UV radiation received by the surface is of the UV-C and UV-B type, which makes Mars a sterilizing planet; despite these circumstances, the scientific community wonders about the possibility that, at some point and under certain seasonal and location factors at certain latitudes of the planet, conditions suitable for the emergence of life may exist. This work is focused on simulating an experimental environment that replicates the solar ultraviolet radiation on Mars, estimating the total solar irradiance for different latitudes and times of the year on the red planet, and thus establishing the effect of these conditions on the germination and photosynthetic pigment content of Chenopodium quinoa, in order to make a pilot study for future colonization and subsistence on the planet. By estimating the total solar irradiance for the different latitudes and times of the year on Mars within its atmosphere, the solar constant for this planet was calculated, in order to then analyze the effect of the attenuation of solar UV radiation and in this way, through the sowing of Chenopodium quinoa materials, it was possible to determine that seeds under stress conditions with ultraviolet radiation of 180 nm, 250 nm and 395 nm, were able to germinate faster than seeds sown in control, indicating that the function of secondary metabolites is able to mediate responses to prolonged exposure to radiation. As for the plants exposed to these conditions, it was established that they are able to withstand wavelengths between 250 nm and 395 nm, with stable photosynthetic functions, showing a high percentage of recovery.

Resumo:

Giant planets with $P > 10$ days, are excellent targets to measure their composition, to characterize their atmospheric abundances and to study their formation and evolution mechanisms, since they are less affected by the stellar irradiation and tidal interactions with the host star, that the hot-Jupiters suffer. We present two transiting planets, in long-period orbits, whose transit signals were detected by TESS, and were further confirmed and characterized using ground-based photometric and spectroscopic data, as part of the WINE collaboration. From the joint analysis we derived the following orbital parameters for TIC4672985b: P = 69.048 d, Mp = 13.25 Mjup, Rp = 1.008 Rjup and e = 0.018. Also, the RVs revealed a trend at the 350 [m/s/yr] level, indicative of the presence of a massive outer companion in the system. This is a unique example of a transiting sub-stellar companion with a mass above the deuterium-burning limit, located beyond 0.1 AU and in a circular orbit. These properties are difficult to reproduce from canonical planet formation and evolution models. In addition, we modeled the interior structure/composition and the radius evolution of this planet, including the effect of the stellar irradiation, using MESA. We found a bulk composition that is consistent with a H/He gas envelope, with no heavy-element enhancement with respect to the host star. Similarly, for TOI-2529b we obtained the following parameters: P = 64.595 d, Mp = 2.33 Mjup, Rp = 1.027 Rjup and e = 0.022, making this object an excellent example of a growing population of transiting Warm-Jupiters. From the MESA models we found that its observed properties are well reproduced by a dense rocky-core surrounded by a H/He with enhanced heavy-elements with respect to the parent stars, which is a indication of a formation process via core-accretion.