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

Rotation Periods of Five Near-Earth Asteroids with the Trappist Telescopes: (17188) 1999 WC2, (242450) 2004 QY2, (503871) 2000 SL, 2023 DZ2 And 2023 CM

editorial reviewedLightcurves of five near-Earth asteroids were obtained with TRAPPIST-North and TRAPPIST-South from December 2022 to May 2023. For all of them the synodic rotation period and amplitude were found to be: (17188) 1999 WC2, (5.064 ± 0.002 h) and (0.35 ± 0.02 mag); (242450) 2004 QY2, (7.072 h ± 0.001 h) and (0.30 ± 0.01 mag); (503871) 2000 SL, (10.6504 h ± 0.0020 h) and (0.32 ± 0.04 mag); 2023 DZ2, (0.104587 ± 0.000083 h) and (0.58 ± 0.02 mag); 2023 CM, (3.6244 ± 0.0004 h) and (0.24 ± 0.02 mag). All data have been submitted to ALCDEF database

Study of Io's sodium jets with the TRAPPIST telescopes

Io is the most volcanically active body in the Solar System. This volcanic activity results in the ejection of material into Io's atmosphere, which may then escape from the atmosphere to form various structures in the jovian magnetosphere, including the plasma torus and clouds of neutral particles. The physical processes involved in the escape of particles - for example, how the volcanoes of Io provide material to the plasma torus - are not yet fully understood. In particular, it is not clear to what extent the sodium jet, one of the sodium neutral clouds related to Io, is a proxy of processes that populate the various reservoirs of plasma in Jupiter's magnetosphere. Here, we report on observations carried out over 17 nights in 2014-2015, 30 nights in 2021, and 23 nights in 2022-2023 with the TRAPPIST telescopes, in which particular attention was paid to the sodium jet and the quantification of their physical properties (length, brightness). It was found that these properties can vary greatly from one jet to another and independently of the position of Io in its orbit. No clear link was found between the presence of jets and global brightening of the plasma torus and extended sodium nebula, indicating that jets do not contribute straightforwardly to their population. This work also demonstrates the advantage of regular and long-term monitoring to understanding the variability of the sodium jet and presents a large corpus of jet detections against which work in related fields may compare.Comment: Alexander de Becker and Linus Head contributed equally to this work and share first authorshi

Photometry of 25 Large Main-belt Asteroids with TRAPPIST-North and -South

editorial reviewedDensely sampled lightcurves of 25 large main-belt asteroids were obtained with the TRAPPIST-South (TS) and TRAPPIST-North (TN) telescopes from 2017 to 2021. Those observations took place in support of an ESO large program aiming at observing a representative sample of large asteroids with the ESO VLT for precise shape determination from adaptive optics high-resolution imaging. Synodic rotation periods and lightcurve amplitudes have been determined for all but one target. Six asteroids were observed during two different apparitions. The data have been submitted to the ALCDEF database

Development in Astronomy and Space Science in Africa

The development of astronomy and space science in Africa has grown significantly over the past few years. These advancements make the United Nations Sustainable Development Goals more achievable, and open up the possibility of new beneficial collaborations.Comment: Paper published in Nature Astronomy. Figures 1 and 2 are included in the published version, that can be seen at https://rdcu.be/2oE

Lightcurve Based Determination of 10 Hygiea'S Rotational Period With Trappist-North and -South

peer reviewedA densely-sampled lightcurve of the large main-belt asteroid 10 Hygiea was obtained with the TRAPPISTSouth (TS) and TRAPPIST-North (TN) telescopes in 2018 September and October. We found its synodic rotation period and amplitude to be 13.8224 ± 0.0005 h and 0.27 mag. The data have been submitted to the ALCDEF database