Observatoire royal de Belgique Koninklijke Sterrenwacht van België Royal Observatory of Belgium Rapport annuel 2018 Jaarverslag 2018 Annual report 2018 Cover illustration: Space Pole Open Door Days 2018. (Credit: Timothy Jans/Royal Observatory of Belgium) Royal Observatory of Belgium – Annual Report 2018 1 De activiteiten beschreven in dit verslag werden ondersteund door Les activités décrites dans ce rapport ont été soutenues par The activities described in this report were supported by De POD Wetenschapsbeleid De Nationale Loterij Le SPP Politique Scientifique La Loterie Nationale The Belgian Science Policy The National Lottery Het Europees Ruimtevaartagentschap De Europese Gemeenschap L’Agence Spatiale Européenne La Communauté Européenne The European Space Agency The European Community Het Fonds voor Wetenschappelijk Onderzoek – Le Fonds de la Recherche Scientifique Vlaanderen Royal Observatory of Belgium – Annual Report 2018 2 Table of contents Preface .................................................................................................................................................... 5 Reference Systems and Planetology ....................................................................................................... 6 Contribution to the European Plate Observing System – EPOS .......................................................... 7 Legal Time ........................................................................................................................................... 8 Rotation and Nutation on a Wobbly Earth ......................................................................................... 9 Radio Science on Mars ...................................................................................................................... 10 LaRa (Lander Radioscience) .......................................................................................................... 10 Participation in the RISE experiment ............................................................................................ 11 Material properties and planetary interiors ..................................................................................... 13 Seismology and Gravimetry .................................................................................................................. 15 Service to society .............................................................................................................................. 16 The expertise of the Observatory in metrology: the redefinition of the kilogram ........................... 17 Identifying sources of earthquakes in a fault zone in Chile .............................................................. 18 Study on vault collapses in the Han-sur-Lesse cave .......................................................................... 19 The LARGE-MEM project ................................................................................................................... 21 Astronomy and Astrophysics ................................................................................................................ 22 Gaia’s second data release................................................................................................................ 23 DPAC ............................................................................................................................................. 23 Solar system objects ..................................................................................................................... 24 Radial velocities ............................................................................................................................ 24 Variability ...................................................................................................................................... 25 Stellar parameter determination .................................................................................................. 25 The archive .................................................................................................................................... 26 Belgo-Indian Network for Astronomy and Astrophysics................................................................... 27 Eclipsing binary system with pulsations: KIC 6048106, a case study from the Kepler space mission .............................................................................................................................................. 29 The real time evolution of Sakurai’s object ...................................................................................... 31 Solar Physics and Space Weather ......................................................................................................... 33 PECASUS, a space weather service for the aviation sector .............................................................. 33 Exploring the Middle Corona ............................................................................................................ 35 First Detection of Solar Flare Emission in Mid-ultraviolet Balmer Continuum ................................. 38 Size distributions of solar proton events and their associated soft X-ray flares based on the maximum likelihood estimator ......................................................................................................... 40 Analysis and Results ...................................................................................................................... 40 Discussion ..................................................................................................................................... 42 Royal Observatory of Belgium – Annual Report 2018 3 Next generation of JHelioviewer ....................................................................................................... 43 DigiSun: a tool to extract scientific data from sunspot drawings ..................................................... 45 Communication and Information ......................................................................................................... 47 The Open Doors Days 2018 ............................................................................................................... 48 Information to the public and authorities ........................................................................................ 48 Website, news, press releases and social media .............................................................................. 49 The Heritage Days at the Ancient Observatory and other exhibitions ............................................. 49 Archives and museum ....................................................................................................................... 50 The Planetarium .................................................................................................................................... 51 Daily activities ................................................................................................................................... 52 Special activities ................................................................................................................................ 52 Annex 1: Publications ............................................................................................................................ 54 Refereed publications ....................................................................................................................... 55 Publications without peer review ..................................................................................................... 68 Other publications ............................................................................................................................ 74 Annex 2: Workforce .............................................................................................................................. 77 Royal Observatory of Belgium – Annual Report 2018 4 Preface This report describes the highlights of scientific activities and public services at the Royal Observatory of Belgium in 2018. A list of publications and the list of personnel are included at the end. Due to lack of means and personnel the report is only in English. If you need more or other information on the Royal Observatory of the Belgium and/or its activities please contact [email protected] or visit our website http://www.astro.oma.be. Ronald Van der Linden Director General Royal Observatory of Belgium – Annual Report 2018 5 Reference Systems and Planetology This Operational Directorate “Reference Systems and Planetology” contributes to the elaboration of reference systems and timescales, integrates Belgium in the international reference frames, and studies the interior, rotation, dynamics, and crustal deformation of the Earth and other terrestrial planets and moons of our solar system The principal activities are grouped into two general themes: 1. Space geodesy and timescales with GNSS (Global Navigation Satellite System), and 2. Rotation and interior structure of the Earth and other terrestrial planets and satellites. Royal Observatory of Belgium – Annual Report 2018 6 Contribution to the European Plate Observing System – EPOS EPOS is one of the European Research Infrastructures in the Environmental research area. It focuses on the solid Earth domain and combines research infrastructures and their capital of human expertise, data, and services into one integrated system. It gathers input from geodesy,