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Chuxian Li, Jeroen E. Sonke, Gaël Le Roux, Natalia Piotrowska, Nathalie Van der Putten, Stephen J. Roberts, Tim Daley, Emma Rice, Roland Gehrels, Maxime Enrico, Dmitri Mauquoy, Thomas P. Roland, François De Vleeschouwer |
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Title |
Unequal Anthropogenic Enrichment of Mercury in Earth’s Northern and Southern Hemispheres |
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Year |
2020 |
Publication |
ACS Earth and Space Chemistry |
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Volume |
4 |
Issue |
11 |
Pages |
2073-2081 |
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Abstract |
Remote Northern Hemisphere (NH) and Southern Hemisphere (SH) lake sediment and peat records of mercury (Hg) deposition have shown a ×3 to ×5 Hg enrichment since pre-industrial times (<1880 AD), leading to the perception that global atmospheric Hg enrichment is moderate and uniform across the hemispheres. Anthropogenic Hg emissions in the NH are, however, approximately 4 times higher than those in the SH. Here, we reconstruct atmospheric Hg deposition in four remote SH peatlands and review sediment and peat Hg records from both hemispheres. We observe a ×4 all-time enrichment in SH Hg deposition from pre-anthropogenic (<1450 AD) to the late 20th-century periods, which is lower than the large ×16 all-time enrichment in NH Hg deposition. We attribute this difference to lower anthropogenic Hg emissions in the SH, and higher natural atmospheric SH Hg concentrations, supported by ×2 higher natural background Hg accumulation in SH peat records. We suggest that the higher SH natural atmospheric Hg deposition reflects the SH land–ocean distribution, and is driven by important SH marine Hg emissions. Our findings indicate that atmospheric Hg background levels and anthropogenic enrichment in both hemispheres are different and should be taken into account in international Hg assessments and environmental policy. |
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1065,1133 |
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Bachelor's thesis |
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yes |
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7791 |
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Chuxian Li, Jeroen E. Sonke, Gaël Le Roux, Nathalie Van der Putten, Natalia Piotrowska, Catherine Jeandel, Nadine Mattielli, Mathieu Benoit, Giles F. S. Wiggs, François De Vleeschouwer |
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Title |
Holocene dynamics of the southern westerly winds over the Indian Ocean inferred from a peat dust deposition record |
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Year |
2020 |
Publication |
Quaternary Science Reviews |
Abbreviated Journal |
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Volume |
231 |
Issue |
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Pages |
106169 |
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Keywords |
Amsterdam Island Anthropogenic activities Dust sources Peat Southern westerly winds |
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Abstract |
The southern westerly winds (SWW) play a major role in climate variability in Southern Hemisphere mid- and high-latitudes, regulating rainfall, ocean circulation, and the Southern Ocean carbon sink. Despite their importance, little is known about millennial scale changes in the SWW and how they have influenced the climate system in the past and interacted with the Earth’s surface elements, such as dust, nutrients and carbon. Here we present a dust record from a 6.6 kyr old peat core in Amsterdam Island (AMS) situated at the northern edge of the SWW (37°S) in the Southern Indian Ocean. Mineral dust flux was used to track atmospheric dust production, long-distance transport and subsequent deposition. Dust provenance was determined from rare earth element (REE) and Nd isotopic signatures (εNd) in the peat core, compared with a reference dataset of Southern Hemisphere dust sources. Using a multi-proxy mixing model, the εNd and REE ratios show a relatively uniform mixture of ca. 40% local, 15% Southern African and 45% Southern South American dust sources since 6.6 cal kyr BP. However, from 1910 AD onwards, there is a doubling in the contribution from Southern Africa (32%). Two mineral dust flux minima occur at 6.2–4.9 cal kyr BP and 3.9–2.7 cal kyr BP, interpreted as periods with equatorward-shifted and/or strengthened SWW at the northern edge of the wind belt. Conversely, periods of higher dust flux at 6.6–6.2 cal kyr BP, 4.9–3.9 cal kyr BP, and 1.4 cal kyr BP onwards are interpreted as poleward-shifted and/or weakened SWW. These interpretations are based on the findings that higher (lower) wind speeds lead to enhanced (less) removal of distal dust on the way to AMS, by wet deposition and turbulence. Published Holocene SWW records at the northern edge of the wind belt (33–41°S) covering South-America, Southern-Africa and Australia, show much variability over the last 6.6 kyr. We suggest this reflects complex regional climate variability in the different SH longitudinal sectors, indicating that SWW are not zonally homogeneous at the northern edge of the wind belt. The recent shift in dust provenance is not accompanied by enhanced total dust deposition at AMS. We therefore suggest that human impact (e.g., land use changes) and drier climate conditions in Southern Africa have led to enhanced dust mobilization. |
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1065,1133 |
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Bachelor's thesis |
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0277-3791 |
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yes |
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8193 |
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L. G. Bouma, J. D. Hartman, R. Brahm, P. Evans, K. A. Collins, G. Zhou, P. Sarkis, S. N. Quinn, J. de Leon, J. Livingston, C. Bergmann, K. G. Stassun, W. Bhatti, J. N. Winn, G. Á Bakos, L. Abe, N. Crouzet, G. Dransfield, T. Guillot, W. Marie-Sainte, D. Mékarnia, A. H. M. J. Triaud, C. G. Tinney, T. Henning, N. Espinoza, A. Jordán, M. Barbieri, S. Nandakumar, T. Trifonov, J. I. Vines, M. Vuckovic, C. Ziegler, N. Law, A. W. Mann, G. R. Ricker, R. Vanderspek, S. Seager, J. M. Jenkins, C. J. Burke, D. Dragomir, A. M. Levine, E. V. Quintana, J. E. Rodriguez, J. C. Smith, B. Wohler |
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Title |
Cluster Difference Imaging Photometric Survey. II. TOI 837: A Young Validated Planet in IC 2602 |
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Journal |
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Year |
2020 |
Publication |
The Astronomical Journal |
Abbreviated Journal |
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Volume |
160 |
Issue |
5 |
Pages |
239 |
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Keywords |
Astrophysics – Earth and Planetary Astrophysics Astrophysics – Solar and Stellar Astrophysics |
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Abstract |
We report the discovery of TOI 837b and its validation as a transiting planet. We characterize the system using data from the NASA TESS mission, the ESA Gaia mission, ground-based photometry from El Sauce and ASTEP400, and spectroscopy from CHIRON, FEROS, and Veloce. We find that TOI 837 is a $T=9.9$ mag G0/F9 dwarf in the southern open cluster IC 2602. The star and planet are therefore $35^{+11}{-5}$ million years old. Combining the transit photometry with a prior on the stellar parameters derived from the cluster color-magnitude diagram, we find that the planet has an orbital period of $8.3\,{\rm d}$ and is slightly smaller than Jupiter ($R{\rm p} = 0.77^{+0.09}{-0.07} \,R{\rm Jup}$). From radial velocity monitoring, we limit $M{\rm p}\sin i$ to less than 1.20 $M{\rm Jup}$ (3-$\sigma$). The transits either graze or nearly graze the stellar limb. Grazing transits are a cause for concern, as they are often indicative of astrophysical false positive scenarios. Our follow-up data show that such scenarios are unlikely. Our combined multi-color photometry, high-resolution imaging, and radial velocities rule out hierarchical eclipsing binary scenarios. Background eclipsing binary scenarios, though limited by speckle imaging, remain a 0.2% possibility. TOI 837b is therefore a validated adolescent exoplanet. The planetary nature of the system can be confirmed or refuted through observations of the stellar obliquity and the planetary mass. Such observations may also improve our understanding of how the physical and orbital properties of exoplanets change in time. |
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1066 |
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1538-3881 |
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yes |
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7804 |
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Nicolas Crouzet, Abdelkrim Agabi, Tristan Guillot, Lyu Abe, François-Xavier Schmider, Djamel Mékarnia, Amaury H. M. J. Triaud, Yves Bresson, Nicolas Mauclert, Christophe Bailet, Dennis Breeveld, Sander Blommaert, Brian Shortt, Jean-Baptiste Daban, Anne-Marie Lagrange, Romain Touzé, Justin Dufour, Valentin Stee, Jocelyn Caruana |
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Title |
Towards ASTEP+, a two-color photometric telescope at Dome C, Antarctica |
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Peer-reviewed symposium |
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2020 |
Publication |
Ground-based and Airborne Instrumentation for Astronomy VIII |
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11447 |
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114470O |
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Dome C, Antarctica is unique in particular for long-duration astronomical observations due to the excellent weather conditions and nearly uninterrupted nights during the Southern winter period. The 40 cm telescope ASTEP has been operating successfully at the Concordia base, at Dome C, since 2010. We describe the new ASTEP+, a major upgrade of its camera box which will allow it to observe simultaneously in two colors. Approximately three times more photons will be collected for science, yielding more sensitive and accurate observations. The southern location of the telescope means that it is ideally located to follow-up exoplanetary targets in preparation for the future JWST and Ariel observations, in particular when located in the southern continuous viewing zones of these space-based telescopes. |
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1066 |
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7803 |
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Crouzet N., Guillot T., Abe L., Mékarnia D., Agabi K., Bresson Y., Bailet C., Mauclert N., Heras A., Ferruit P., Triaud A., Lagrange A., Schmider ., Giardino G., Isaak K., Kohley R., Michalik D., Foing B., Pilbratt G., Stankov A., Gondoin P., Birkmann S., O'Rourke L. |
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Title |
Two-colour photometry to search for transiting exoplanets with ASTEP at Dome C, Antarctica |
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Communication |
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Year |
2020 |
Publication |
Scar 2020 open science conference |
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Dome C in Antarctica provides exceptional conditions for photometry thanks to the continuous night during the Antarctic winter, a high clear sky fraction, low wind speeds, and a cold and dry atmosphere. The ASTEP project (Antarctic Search for Transiting ExoPlanets) aims at detecting and characterising transiting exoplanets and qualifying this site for photometry in the visible. The main instrument, a 40 cm telescope, has been designed to perform high precision photometry under the extreme conditions of the Antarctic winter and has operated at the Concordia station since 2010. It will be upgraded with two new cameras and a new camera box in order to provide simultaneous two-colour photometry and substantially increase its throughput. The new setup will be operational for the winter campaign 2021 and will allow us to discover transiting exoplanets orbiting bright stars in particular low mass exoplanets, temperate exoplanets, exoplanets around young stars, and to refine the ephemerides of exoplanets discovered by the TESS mission. These observations will provide targets for first characterisation with the CHEOPS mission and atmospheric studies with the JWST and ARIEL missions. In this talk, I will describe the science goals and the upgrade of the ASTEP telescope. |
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1066 |
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yes |
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7806 |
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Crouzet N., Mékarnia D., Agabi K., Guillot T., Abe L., Bayliss D., Deeg H., Murgas F., Palle E., Schmider F. |
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Title |
Searching for long period transiting exoplanets with ASTEP South at Dome C, Antarctica |
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Book Chapter |
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2020 |
Publication |
SCAR 2020 Open Science Conference (abstract only) |
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Much of our understanding of gas giant exoplanets come from those transiting in front of bright stars at short orbital separations (P ~ 3 days, a ~ 0.05 au). However, these |
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1066 |
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Bachelor's thesis |
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yes |
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7807 |
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Author |
Martischang J-P. |
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Title |
Exoplanètes : sélection de calibrateurs et ajustements de transits |
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Master |
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Year |
2020 |
Publication |
Master, Ecole Nationale d'art et Métiers (ENSAM), Paris, juin-août 2020 |
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1066 |
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Bachelor's thesis |
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yes |
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7817 |
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Author |
E. Aristidi, A. Agabi, L. Abe, E. Fossat, A. Ziad, D. Mékarnia |
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Title |
Dome C coherence time statistics from DIMM data |
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Journal |
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Year |
2020 |
Publication |
Monthly Notices of the Royal Astronomical Society |
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Volume |
496 |
Issue |
4 |
Pages |
4822-4826 |
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Keywords |
Astrophysics – Instrumentation and Methods for Astrophysics |
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Abstract |
We present a reanalysis of several years of DIMM data at the site of Dome C, Antarctica, to provide measurements of the coherence time $\tau0$. Statistics and seasonal behaviour of $\tau0$ are given at two heights above the ground, 3m and 8m, for the wavelength $\lambda=500$nm. We found an annual median value of $2.9$ms at the height of 8m. A few measurements could also be obtained at the height of 20m and give a median value of 6ms during the period June--September. For the first time, we provide measurements of $\tau0$ in daytime during the summer, which appears to show the same time dependence as the seeing with a sharp maximum at 5pm local time. Exceptional values of $\tau0$ above 10ms are met at this particular moment. The continuous slow variations of turbulence conditions during the day offers a natural test bed for a solar adaptive optics system. |
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1066 |
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0035-8711, 1365-2966 |
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0035-8711, 1365-2966 |
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7825 |
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Crouzet, N., Guillot T., Abe L., Mékarnia D., Agabi A., Schmider F.-X., Vauglin I. |
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Title |
Astronomie à Concordia : projets et besoins |
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2020 |
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Prospective INSU 2020, 6 février 2020, Paris, France |
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1066 |
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Bachelor's thesis |
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7828 |
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Author |
Guillot T. |
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Title |
Discovering Exoplanets from Antarctica with ASTEP |
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Conference - International - Communication |
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Year |
2020 |
Publication |
On the way to Antarctica seminar, 29 october 2020 |
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1066 |
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Bachelor's thesis |
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yes |
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7829 |
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