Surface pressure impact on nitrogen-dominated USP super-Earth atmospheres

In this paper, we compare the chemistry and the emission spectra of nitrogen-dominated cool, warm, and hot ultra-short-period (USP) super-Earth atmospheres in and out of chemical equilibrium at various surface pressure scenarios ranging from 0.1 to 10 bar. We link the one-dimensional VULCAN chemical kinetic code, in which thermochemical kinetic and vertical transport and photochemistry are taken into account, to the one-dimensional radiative transfer model, PETITRADTRANS, to predict the emission spectra of these planets. The radiative-convective temperature-pressure profiles were computed with the HELIOS code. Then, using PANDEXO noise simulator, we explore the observability of the differences produced by disequilibrium processes with the JWST. Our grids show how different surface pressures can significantly affect the temperature profiles, the atmospheric abundances, and consequently the emission spectra of these planets. We find that the divergences due to disequilibrium processes would be possible to observe in cooler planets by targeting HCN, C2H4, and CO, and in warmer planets by targeting CH4 with HCN, using the NIRSpec and MIRI LRS JWST instruments. These species are also found to be sensitive indicators of the existence of surfaces on nitrogen-dominated USP super-Earths, providing information regarding the thickness of these atmospheres.Comment: 12 page

Interferometric apodization by homothety -- I. Optimization of the device parameters

This study is focused on the very high dynamic imaging field, specifically the direct observation of exoplanetary systems. The coronagraph is an essential technique for suppressing the star's light, making it possible to detect an exoplanet with a very weak luminosity compared to its host star. Apodization improves the rejection of the coronagraph, thereby increasing its sensitivity. This work presents the apodization method by interferometry using homothety, with either a rectangular or circular aperture. We discuss the principle method, the proposed experimental setup, and present the obtained results by optimizing the free parameters of the system while concentrating the maximum of the light energy in the central diffraction lobe, with a concentration rate of 93.6\% for the circular aperture and 91.5\% for the rectangular geometry. The obtained results enabled scaling the various elements of the experiment in accordance with practical constraints. Simulation results are presented for both circular and rectangular apertures. We performed simulations on a hexagonal aperture, both with and without a central obstruction, as well as a segmented aperture similar to the one used in the Thirty Meter Telescope (TMT). This approach enables the attainment of a contrast of approximately $10^{-4}$ at small angular separations, specifically around $1.8\lambda/D$. When integrated with a coronagraph, this technique exhibits great promise. These findings confirm that our proposed technique can effectively enhance the performance of a coronagraph.Comment: 10 pages, 14 figure

Monitoring the activity and composition of comet C/2017K2 (PanSTARRS) with TRAPPIST telescopes

We report on the results of a long photometry and monitoring of comet C/2017 K2 (PanSTARRS), hereafter 17K2, with the TRAPPIST telescopes [1]. 17K2 is an Oort cloud comet discovered by the Pan-STARRS survey in 2017 [2], at a large heliocentric distance of 16 au. The comet was later identified in archival imagery to be active at 23.8 au from the Sun, the second most distant discovery of an active comet [3]. It has been claimed that 17K2 is a rare CO-rich comet [4]. We started observing 17K2 with TRAPPIST-North on October 25, 2017 using broad-band filters when the comet was at 15 au from the Sun with a magnitude of 18. We started collecting broad and narrow-band images [5] with TRAPPIST-South on September 9, 2021 (rh=5.4 au) when the comet became visible and bright from the southern hemisphere. The comet will reach its perihelion on December 19, 2022 at rh=1.8 au, and we will monitor its activity on both sides of perihelion. As writing this abstract, we detected emission of CN, C2, and C3 radicals as well as the dust continuum in four bands. By fitting the observed gas profiles with Haser model [6] after subtraction of the dust continuum, we derived the gas production rates for a different detected species. From the continuum and broad-bands images, we computed the Afρ parameter, and a dust production proxy [7]. In this work, we will show the magnitude evolution of this comet over 4 years (2017-2022), as well as the gas and dust activity for several months as a function of heliocentric distances

WASP-193b: An extremely low-density super-Neptune

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WASP-193b: An extremely low-density super-Neptune

Gas giants transiting bright nearby stars are stepping stones for our understanding of planetary system formation and evolution mechanisms. This paper presents a particularly interesting new specimen of this kind of exoplanet discovered by the WASP-South transit survey, WASP-193b. This planet completes an orbit around its Vmag = 12.2 F9 main-sequence host star every 6.25 d. Our analyses found that WASP-193b has a mass of Mp = 0.139 +/- 0.029 M_Jup and a radius of Rp = 1.464 +/- 0.058 R_ Jup, translating into an extremely low density of rhop = 0.059 +\- 0.014 g/cm^3. The planet was confirmed photometrically by the 0.6-m TRAPPIST-South, the 1.0-m SPECULOOS-South telescopes, and the TESS mission, and spectroscopically by the ESO-3.6-m/HARPS and Euler-1.2-m/CORALIE spectrographs. The combination of its large transit depth (dF~1.4 %), its extremely-low density, its high-equilibrium temperature (Teq = 1254 +/- 31 K), and the infrared brightness of its host star (magnitude Kmag=10.7) makes WASP-193b an exquisite target for characterization by transmission spectroscopy (transmission spectroscopy metric: TSM ~ 600). One single JWST transit observation would yield detailed insights into its atmospheric properties and planetary mass, within ~0.1 dex and ~1% (vs ~20% currently with radial velocity data) respectively

An extended low-density atmosphere around the Jupiter-sized planet WASP-193 b

Gas giants transiting bright nearby stars provide crucial insights into planetary system formation and evolution mechanisms. Most of these planets show certain average characteristics, serving as benchmarks for our understanding of planetary systems. However, outliers like the planet we present in this study, WASP-193 b, offer unique opportunities to explore unconventional formation and evolution processes. This planet completes an orbit around its V-band-magnitude 12.2 F9 main-sequence host star every 6.25 days. Our analyses found that WASP-193 b has a mass of 0.139 ± 0.029 MJ and a radius of 1.464 ± 0.058 RJ, translating into an extremely low density of 0.059 ± 0.014g cm−3, at least one order of magnitude less than standard gas giants like Jupiter. Typical gas giants such as Jupiter have densities that range between 0.2 g cm−3 and 2 g cm−3. The combination of its large transit depth (1.4%), extremely low density, high-equilibrium temperature (1,254 ± 31 K) and the infrared brightness of its host star (K-band magnitude 10.7) makes WASP-193 b an exquisite target for characterization by transmission spectroscopy (transmission spectroscopy metric ~600). One single JWST transit observation would yield detailed insights into its atmospheric properties and planetary mass, providing a unique window to explore the mechanisms behind its exceptionally low density and shed light on giant planets' diverse nature