S. Hellmich
A5060949047- Astro and Planetary Science
- Stellar, planetary, and galactic studies
- Planetary Science and Exploration
- Gamma-ray bursts and supernovae
- Astrophysics and Star Formation Studies
- SAS software applications and methods
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Isotope Analysis in Ecology
- GNSS positioning and interference
- Space Science and Extraterrestrial Life
- Space exploration and regulation
- Astrophysical Phenomena and Observations
- Distributed and Parallel Computing Systems
- High-pressure geophysics and materials
- Numerical methods for differential equations
- Geological and Geochemical Analysis
- Space Exploration and Technology
- Geology and Paleoclimatology Research
- Advanced X-ray and CT Imaging
- Pulsars and Gravitational Waves Research
- Economic and Technological Innovation
- Paleopathology and ancient diseases
- Adaptive optics and wavefront sensing
- Scientific Research and Discoveries
École Polytechnique Fédérale de Lausanne
2022-2024
Planet
2013-2022
Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR)
2013-2020
Institut für Lungenforschung
2014
Dienstleistungszentrum Ländlicher Raum
2013
Short duration gamma-ray bursts (SGRBs) are thought to be related the violent merger of compact objects, such as neutron stars or black holes, which makes them promising sources gravitational waves. The detection a 'kilonova'-like signature associated Swift-detected GRB 130603B has suggested that this event is result object merger. Our knowledge on SGRB been, until now, mostly based absence supernova signatures and analysis host galaxies they cannot always securely associated. Further...
Context. Asteroid modeling efforts in the last decade resulted a comprehensive dataset of almost 400 convex shape models and their rotation states. These already provided deep insight into physical properties main-belt asteroids or large collisional families. Going finer detail (e.g., smaller families, with sizes ≲20 km) requires knowledge parameters more objects.
The larger number of models asteroid shapes and their rotational states derived by the lightcurve inversion give us better insight into both nature individual objects whole population. With a statistical sample we can study physical properties populations, such as main-belt asteroids or families, in more detail. Shape also be used combination with other types observational data (IR, adaptive optics images, stellar occultations), e.g., to determine sizes thermal properties. We use all...
There have been previous hints that the transiting planet WASP-3 b is accompanied by a second in nearby orbit, based on small deviations from strict periodicity of observed transits. Here we present 17 precise radial velocity measurements and 32 transit light curves were acquired between 2009 2011. These data used to refine parameters host star planet. This has resulted reduced uncertainties for radii masses The radial-velocity times show no evidence an additional system. Therefore,...
As part of our ongoing effort to investigate transit timing variations (TTVs) known exoplanets, we monitored transits the four exoplanets HAT-P-18b, HAT-P-19b, HAT-P-27b/WASP-40b and WASP-21b. All them are suspected show TTVs due properties their host systems based on respective discovery papers. During past three years 46 observations were carried out, mostly using telescopes Young Exoplanet Transit Initiative. The analyses used refine systems' orbital parameters. In all cases found no...
Abstract We use our new light curves, along with historical data, to determine the rotation state, photometric properties, and convex shape models of targets Lucy mission (3548) Eurybates (21900) Orus. a retrograde spin for both targets, sidereal periods 8.7027283 ± 0.0000029 h 13.486190 0.000017 h, respectively. The phase curves objects are nearly linear in phase-angle range observable from Earth lack pronounced opposition effect. Unsupervised classification these by Penttilä et al. tool...
Context. Trans-Neptunian objects (TNOs) are important bodies, but very little is known about their basic physical properties such as size, density, and albedo.
On 28th January 2018, the large Trans-Neptunian Object (TNO) 2002TC302 occulted a m$_v= $15.3 star with ID 130957813463146112 in Gaia DR2 stellar catalog. 12 positive occultation chords were obtained from Italy, France, Slovenia and Switzerland. Also, 4 negative detections near north south limbs. This represents best observed by TNO other than Pluto, terms of number published thus far. From chords, an accurate elliptical fit to instantaneous projection body, compatible misses, can be...
Events such as GRB130606A at z=5.91, offer an exciting new window into pre-galactic metal enrichment in these very high redshift host galaxies. We study the environment and galaxy of GRB 130606A, a high-z event, context population GRBs. have obtained multiwavelength observations from radio to gamma-ray, concentrating particularly on X-ray evolution well optical photometric spectroscopic data analysis. With initial Lorentz bulk factor range Γ_0 ~ 65-220, afterglow can be explained by...
Abstract We report new photometric lightcurve observations of the Lucy Mission target (11351) Leucus acquired during 2017, 2018, and 2019 apparitions. use these data in combination with stellar occultations captured five epochs to determine sidereal rotation period, spin axis orientation, a convex shape model, absolute scale object, its geometric albedo, model properties target. find that is prograde rotator located within sky-projected radius 3° (1 σ ) from J2000 Ecliptic coordinates ( λ =...
Abstract Thermal infrared observations are the most effective way to measure asteroid diameter and albedo for a large number of near-Earth objects (NEOs). Major surveys like NEOWISE, NEOSurvey, ExploreNEOs, NEOLegacy find small fraction high that do not have clear analogs in current meteorite population. About 8% Spitzer -observed NEOs nominal solutions greater than 0.5. This may be result light-curve variability leading an incorrect estimate or inaccurate absolute visual magnitudes. For...
Dynamically different groups of comets and active asteroids with orbits at 2 - 5 a. u. show dust activity in varying degrees forms. Photometric study comparison physical parameters can help to classify mechanisms nature the for such objects. We present new observations using broadband photometry 15 objects main asteroid belt surrounding regions obtained during 2012 2016. The aims compare properties main-belt (MBCs), quasi-Hilda (QHCs), (AAs). were carried out 0.7-m telescope Kyiv Comet...
The Maria family is regarded as an old-type (∼3 ± 1 Gyr) asteroid that has experienced substantial collisional and dynamical evolution in the main belt. It located near 3:1 Jupiter mean-motion resonance area supplies near-Earth asteroids to inner solar system. We carried out observations of during 134 nights from 2008 July 2013 May derived synodic rotational periods for 51 objects, including newly obtained 34 asteroids. found there a significant excess fast slow rotators observed rotation...
Abstract We performed a unique Venus observation campaign to measure the disk brightness of over broad range wavelengths in 2020 August and September. The primary goal was investigate absorption properties unknown absorber clouds. secondary extract mean SO 2 gas abundance, whose spectral feature is entangled with that at ultraviolet wavelengths. A total three spacecraft six ground-based telescopes participated this campaign, covering 52–1700 nm wavelength range. After careful evaluation...
ABSTRACT We predicted a stellar occultation of the bright star Gaia DR1 4332852996360346368 (UCAC4 385-75921) (mV = 14.0 mag) by centaur 2002 GZ32 for 2017 May 20. Our latest shadow path prediction was favourable to large region in Europe. Observations were arranged broad inside nominal path. Series images obtained with 29 telescopes throughout Europe and from six them (five Spain one Greece) we detected occultation. This is fourth centaur, besides Chariklo, Chiron, Bienor, which multichord...
Within our program of physical characterization trans-Neptunian objects and centaurs, we predicted a stellar occultation by the centaur (54598) Bienor to occur on January 11, 2019, with good observability potential. We obtained high accuracy astrometric data refine prediction, resulting in shadow path favorable for Iberian Peninsula. This encouraged us carry out an observation campaign that resulted five positive detections from four observing sites. is fourth which multichord (more than two...
Aims. We investigate the influence of Yarkovsky force on long-term orbital evolution Jupiter Trojan asteroids. Methods. Clones observed population with different sizes and thermal properties were numerically integrated for 1 Gyr without effect. The escape rate these objects from region as well changes in libration amplitude, eccentricity, inclination used a metric strength effect orbits. Results. Objects radii $R\leq$1 km are significantly influenced by force. causes depletion over...