129 research outputs found
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
at small angular separations, specifically around . 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
- …