333 research outputs found
Groundbased observational campaigns of NEAs
International audienceNEAs observation are important and circumscribe several scientific objectives such are: i) discovery of new objects; ii) confirmation of NEAs newly discovered; iii) secure large uncertainties orbits of NEAs; iv) shape determination from lightcurve analysis; v) scientific interest of specific objects potentially targets of "in-situ" investigations
Giant barocaloric effect in all-d-metal Heusler shape memory alloys
We have studied the barocaloric properties associated with the martensitic transition of a shape memory Heulser alloy Ni50Mn31.5Ti18.5 which is composed of all-d-metal elements. The composition of the sample has been tailored to avoid long range ferromagnetic order in both ausenite and martensite. The lack of ferromagnetism results in a weak magnetic contribution to the total entropy change thereby leading to a large transition entropy change. The combination of such a large entropy change and a relatively large volume change at the martensitic transition gives rise to giant barocaloric properties in this alloy. When compared to other shape memory Heusler alloys, our material exhibits values for adiabatic temperature and isothermal entropy changes significantly larger than values reported so far for this class of materials. Furthermore, our Ni50Mn31.5Ti18.5 also compares favourably to the best state-of-the-art magnetic barocaloric materials.Peer ReviewedPostprint (author's final draft
Long-lasting activity of asteroid (248370) 2005 QN 173
We present the results of observations of asteroid (248370) QN
obtained during July 2021 - January 2022 with three telescopes. Our analysis
revealed the presence of the dust tail for about half of a year. The direct
images of the asteroid were obtained with broad-band filters. No emissions were
revealed in the spectra, and the spectrum of the asteroid closely matched that
of a C-type asteroid. Created color and linear polarization variations along
the tail were analyzed. The asteroid demonstrated a redder color compared to
the Sun. Dramatic changes in dust productivity obtained in different filters
were not detected. The color changes from to over the
coma, and the linear polarization degree varies from about \% to \%
and from \% to \% at the phase angle of and
. The total dust mass ejected until the latest observation on
October 10 is ~kg, with a maximum rate of 2.6~kg\,s
based on the Monte Carlo modeling of the dust tail. The estimated asteroid size
is 1.3~km. It is shown that large particles are concentrated around the
nucleus, whereas smaller ones dominate in the tail. The evolution of (248370)
QN orbit and the orbits of the sample of the 464 short-periodic comets
were followed. Ten of them approached the asteroid's orbit. These objects are
not genetically related, despite the very close distance of their orbits for a
relatively long time.Comment: pages 13; 5 tables; figures 1
Astrocladistics of the Jovian Trojan swarms
The Jovian Trojans are two swarms of small objects that share Jupiter's orbit, clustered around the leading and trailing Lagrange points, L4 and L5. In this work, we investigate the Jovian Trojan population using the technique of astrocladistics, an adaptation of the 'tree of life' approach used in biology. We combine colour data from WISE, SDSS, Gaia DR2, and MOVIS surveys with knowledge of the physical and orbital characteristics of the Trojans, to generate a classification tree composed of clans with distinctive characteristics. We identify 48 clans, indicating groups of objects that possibly share a common origin. Amongst these are several that contain members of the known collisional families, though our work identifies subtleties in that classification that bear future investigation. Our clans are often broken into subclans, and most can be grouped into 10 superclans, reflecting the hierarchical nature of the population. Outcomes from this project include the identification of several high priority objects for additional observations and as well as providing context for the objects to be visited by the forthcoming Lucy mission. Our results demonstrate the ability of astrocladistics to classify multiple large and heterogeneous composite survey data sets into groupings useful for studies of the origins and evolution of our Solar system
Near-Earth Asteroids Data mining on Astronomical Databases: EuroNEAR experience
Program available at: http://www.imcce.fr/hosted_sites/naroo/program.htmlInternational audienceIn the framework of EuroNEAR network several databases around the world were datamined. The main scientifi c objective was the astrometry of Near-Earth Asteroids (NEAs) for both precovery and secure orbits of these objects. The article presents few aspects of data-mining and the developed procedures for accomplishing these objectives
Discovery and physical characterization as the first response to a potential asteroid collision: The case of 2023 DZ2
Near-Earth asteroids (NEAs) that may evolve into impactors deserve detailed
threat assessment studies. Early physical characterization of a would-be
impactor may help in optimizing impact mitigation plans. We first detected NEA
2023~DZ on 27--February--2023. After that, it was found to have a Minimum
Orbit Intersection Distance (MOID) with Earth of 0.00005~au as well as an
unusually high initial probability of becoming a near-term (in 2026) impactor.
We aim to perform a rapid but consistent dynamical and physical
characterization of 2023~DZ as an example of a key response to mitigate
the consequences of a potential impact. We use a multi-pronged approach,
drawing from various methods (observational/computational) and techniques
(spectroscopy/photometry from multiple instruments), and bringing the data
together to perform a rapid and robust threat assessment.} The visible
reflectance spectrum of 2023~DZ is consistent with that of an X-type
asteroid. Light curves of this object obtained on two different nights give a
rotation period =6.27430.0005 min with an amplitude
=0.570.14~mag. We confirm that although its MOID is among the smallest
known, 2023~DZ will not impact Earth in the foreseeable future as a
result of secular near-resonant behaviour. Our investigation shows that
coordinated observation and interpretation of disparate data provides a robust
approach from discovery to threat assessment when a virtual impactor is
identified. We prove that critical information can be obtained within a few
days after the announcement of the potential impactor.Comment: Accepted for publication in Astronomy and Astrophysics, 15 page
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