Thermal properties of large main-belt asteroids observed by Herschel PACS

Non-resolved thermal infrared observations enable studies of thermal and physical properties of asteroids via thermo-physical models provided the shape and rotational properties of the target are well determined. We used calibration-programme Herschel PACS data (70, 100, 160 μm) and state-of-the-art shape models derived from adaptive-optics observations and/or optical light curves to constrain for the first time the thermal inertia of twelve large main-belt asteroids. We also modelled previously well-characterised targets such as (1) Ceres or (4) Vesta as they constitute important benchmarks. Using the scale as a free parameter, most targets required a re-scaling ~5% consistent with what would be expected given the absolute calibration error bars. This constitutes a good cross-validation of the scaled shape models, although some targets required larger re-scaling to reproduce the IR data. We obtained low thermal inertias typical of large main belt asteroids studied before, which continues to give support to the notion that these surfaces are covered by fine-grained insulating regolith. Although the wavelengths at which PACS observed are longwards of the emission peak for main-belt asteroids, they proved to be extremely valuable to constrain size and thermal inertia and not too sensitive to surface roughness. Finally, we also propose a graphical approach to help examine how different values of the exponent used for scaling the thermal inertia as a function of heliocentric distance (i.e. temperature) affect our interpretation of the results.

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Physical parameters of selected Gaia mass asteroids

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936380 ◽

2020 ◽

Vol 638 ◽

pp. A11

Author(s):

E. Podlewska-Gaca ◽

A. Marciniak ◽

V. Alí-Lagoa ◽

P. Bartczak ◽

T. G. Müller ◽

...

Keyword(s):

Thermal Inertia ◽

Physical Property ◽

Physical Parameters ◽

Good Precision ◽

Main Belt ◽

Shape Models ◽

Solar System Bodies ◽

Fundamental Physical Property ◽

Thermophysical Modeling ◽

The Masses

Context. Thanks to the Gaia mission, it will be possible to determine the masses of approximately hundreds of large main belt asteroids with very good precision. We currently have diameter estimates for all of them that can be used to compute their volume and hence their density. However, some of those diameters are still based on simple thermal models, which can occasionally lead to volume uncertainties as high as 20–30%. Aims. The aim of this paper is to determine the 3D shape models and compute the volumes for 13 main belt asteroids that were selected from those targets for which Gaia will provide the mass with an accuracy of better than 10%. Methods. We used the genetic Shaping Asteroids with Genetic Evolution (SAGE) algorithm to fit disk-integrated, dense photometric lightcurves and obtain detailed asteroid shape models. These models were scaled by fitting them to available stellar occultation and/or thermal infrared observations. Results. We determine the spin and shape models for 13 main belt asteroids using the SAGE algorithm. Occultation fitting enables us to confirm main shape features and the spin state, while thermophysical modeling leads to more precise diameters as well as estimates of thermal inertia values. Conclusions. We calculated the volume of our sample of main-belt asteroids for which the Gaia satellite will provide precise mass determinations. From our volumes, it will then be possible to more accurately compute the bulk density, which is a fundamental physical property needed to understand the formation and evolution processes of small Solar System bodies.

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Spatially Consistent High-Resolution Land Surface Temperature Mosaics for Thermophysical Mapping of the Mojave Desert

Sensors ◽

10.3390/s19122669 ◽

2019 ◽

Vol 19 (12) ◽

pp. 2669 ◽

Cited By ~ 3

Author(s):

Scott A. Nowicki ◽

Richard D. Inman ◽

Todd C. Esque ◽

Kenneth E. Nussear ◽

Christopher S. Edwards

Keyword(s):

Surface Temperature ◽

Land Surface Temperature ◽

Land Surface ◽

Mojave Desert ◽

Thermal Inertia ◽

Infrared Observations ◽

Fine Grained ◽

Thermal Environments ◽

Landsat 7 ◽

Geomorphic Units

Daytime and nighttime thermal infrared observations acquired by the ASTER and MODIS instruments onboard the NASA Terra spacecraft have produced a dataset that can be used to map thermophysical properties across large regions, which have implications on surface processes, thermal environments and habitat suitability for desert species. ASTER scenes acquired between 2004 and 2012 are combined using new mosaicking and data-fusion techniques to produce a map of daytime and nighttime land surface temperature with coverage exclusive of the effects of clouds and weather. These data are combined with Landsat 7 visible imagery to generate a consistent map of apparent thermal inertia (ATI), which is related to the presence of exposed bedrock, rocks, fine-grained sediments and water on the surface. The resulting datasets are compared to known geomorphic units and surface types to generate an interpreted mechanical composition map of the entire Mojave Desert at 100 m per pixel that is most sensitive to large clast size distinctions in grain size distribution.

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Thermophysical Characteristics of OSIRIS-REx Target Asteroid (101955) Bennu

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315006985 ◽

2015 ◽

Vol 10 (S318) ◽

pp. 218-220

Author(s):

Liangliang Yu ◽

Jianghui Ji

Keyword(s):

Grain Size ◽

Thermal Inertia ◽

Effective Diameter ◽

Thermophysical Characteristics ◽

Shape Model ◽

Infrared Observations ◽

Fine Grained ◽

Thermophysical Model ◽

Best Fit ◽

Geometric Albedo

AbstractIn this work, we investigate the thermophysical properties, including thermal inertia, roughness fraction and surface grain size of OSIRIS-REx target asteroid (101955) Bennu by using a thermophysical model with the recently updated 3D radar-derived shape model (Nolan et al., 2013) and mid-infrared observations (Müller et al. 2012, Emery et al., 2014). We find that the asteroid bears an effective diameter of 510+6−40 m, a geometric albedo of 0.047+0.0083−0.0011, a roughness fraction of 0.04+0.26−0.04, and thermal inertia of 240+440−60 Jm−2s−0.5K−1 for our best-fit solution. The best-estimate thermal inertia suggests that fine-grained regolith may cover a large portion of Bennu's surface, where a grain size may vary from 1.3 to 31 mm. Our outcome suggests that Bennu is suitable for the OSIRIS-REx mission to return samples to Earth.

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Sizes of main-belt asteroids by combining shape models and Keck adaptive optics observations

Icarus ◽

10.1016/j.icarus.2013.07.023 ◽

2013 ◽

Vol 226 (1) ◽

pp. 1045-1057 ◽

Cited By ~ 35

Author(s):

J. Hanuš ◽

F. Marchis ◽

J. Ďurech

Keyword(s):

Adaptive Optics ◽

Main Belt ◽

Shape Models

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Electrodeposition of Copper and Brass Coatings with Olive-Like Structure

Materials ◽

10.3390/ma14071762 ◽

2021 ◽

Vol 14 (7) ◽

pp. 1762

Author(s):

Artur Maciej ◽

Natalia Łatanik ◽

Maciej Sowa ◽

Izabela Matuła ◽

Wojciech Simka

Keyword(s):

Corrosion Resistance ◽

Cathodic Current Density ◽

Bath Composition ◽

Cathodic Current ◽

Corrosion Properties ◽

Fine Grained ◽

Electrodeposited Coating ◽

Copper Zinc ◽

New Generation ◽

First Time

One method of creating a brass coating is through electrodeposition, which is most often completed in cyanide galvanic baths. Due to their toxicity, many investigations focused on the development of more environmentally friendly alternatives. The purpose of the study was to explore a new generation of non-aqueous cyanide-free baths based on 1-ethyl-3-methylimidazolium acetate ionic liquids. The study involved the formation of copper, zinc, and brass coatings. The influence of the bath composition, cathodic current density, and temperature was determined. The obtained coatings were characterized in terms of their morphology, chemical composition, phase composition, roughness, and corrosion resistance. It was found that the structure of the obtained coatings is strongly dependent on the process parameters. The three main structure types observed were as follows: fine-grained, porous, and olive-like. To the best knowledge of the authors, it is the first time the olive-like structure was observed in the case of an electrodeposited coating. The Cu-Zn coatings consisted of 19–96 at. % copper and exhibited relatively good corrosion resistance. A significant improvement of corrosion properties was found in the case of copper and brass coatings with the olive-like structure.

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The effect of stellar multiplicity on protoplanetary discs: a near-infrared survey of the Lupus star-forming region

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3674 ◽

2020 ◽

Vol 501 (2) ◽

pp. 2305-2315

Author(s):

Alice Zurlo ◽

Lucas A Cieza ◽

Megan Ansdell ◽

Valentin Christiaens ◽

Sebastián Pérez ◽

...

Keyword(s):

Adaptive Optics ◽

Molecular Cloud ◽

Near Infrared ◽

Main Sequence Stars ◽

Multiple Systems ◽

Star Forming ◽

Very Large Telescope ◽

Pms Stars ◽

First Time ◽

Infrared Survey

ABSTRACT We present results from a near-infrared (NIR) adaptive optics (AO) survey of pre-main-sequence stars in the Lupus molecular cloud with NACO at the Very Large Telescope (VLT) to identify (sub)stellar companions down to ∼20-au separation and investigate the effects of multiplicity on circumstellar disc properties. We observe for the first time in the NIR with AO a total of 47 targets and complement our observations with archival data for another 58 objects previously observed with the same instrument. All 105 targets have millimetre Atacama Large Millimetre/sub-millimetre Array (ALMA) data available, which provide constraints on disc masses and sizes. We identify a total of 13 multiple systems, including 11 doubles and 2 triples. In agreement with previous studies, we find that the most massive (Mdust > 50 M⊕) and largest (Rdust > 70 au) discs are only seen around stars lacking visual companions (with separations of 20–4800 au) and that primaries tend to host more massive discs than secondaries. However, as recently shown in a very similar study of >200 PMS stars in the Ophiuchus molecular cloud, the distributions of disc masses and sizes are similar for single and multiple systems for Mdust < 50 M⊕ and radii Rdust < 70 au. Such discs correspond to ∼80–90 per cent of the sample. This result can be seen in the combined sample of Lupus and Ophiuchus objects, which now includes more than 300 targets with ALMA imaging and NIR AO data, and implies that stellar companions with separations >20 au mostly affect discs in the upper 10${{\ \rm per\ cent}}$ of the disc mass and size distributions.

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The first finding of a Greek amphora in Poland

Praehistorische Zeitschrift ◽

10.1515/pz-2021-0006 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Sylwester Czopek ◽

Katarzyna Trybała-Zawiślak ◽

Joanna Trąbska ◽

Barbara Trybalska ◽

Joanna Adamik-Proksa ◽

...

Keyword(s):

Trace Elements ◽

Forest Steppe ◽

Iron Compounds ◽

Fine Grained ◽

Tof Sims ◽

First Finding ◽

High Calcium ◽

The University ◽

First Time ◽

North Western

Abstract In 2017, an expedition of the Institute of Archeology of the University of Rzeszów (Poland) carried out excavations on a hillfort belonging to the Scythian cultural circle (its forest-steppe variant) in Chotyniec, in south-eastern Poland. The hillfort is the central and most important point of a large settlement cluster, which is the furthest north-western enclave of this cultural circle. In an excavated cult object – the so-called ‘zolnik’ – we made an interesting discovery. Here we show this unique finding for the first time: a Greek wine amphora, from the beginning of the sixth century BC. We were able to explore and reconstruct it almost entirely. Amphora is the only artefact of this type found in the present Polish borders. The amphora was subjected to archaeometric research with the use of PLM, SEM/EDS, TXRF and ToF SIMS. The massive fabric was made of high calcium clay enriched in quartz and volcanic lithoclasts. The lack of chromium and nickel among trace elements makes the vessel different from the amphoras from the Eastern Meditteranean analysed so far, suggesting a specific workshop. Red painting was executed with very fine grained iron compounds predominantly based on aluminosilicates, enriched in phosphorus. Obviously, since it is associated with the presence of Scythians in Eastern Europe, it simultaneously delimits (geography-wise) the borders of Greek influence.

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Orbital and atmospheric characterization of the planet within the gap of the PDS 70 transition disk

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833584 ◽

2018 ◽

Vol 617 ◽

pp. L2 ◽

Cited By ~ 66

Author(s):

A. Müller ◽

M. Keppler ◽

Th. Henning ◽

M. Samland ◽

G. Chauvin ◽

...

Keyword(s):

Adaptive Optics ◽

Near Infrared ◽

Direct Detection ◽

Spectral Energy Distribution ◽

Spectral Energy ◽

Infrared Range ◽

Data Set ◽

Cloud Properties ◽

Spectrophotometric Data ◽

First Time

Context. The observation of planets in their formation stage is a crucial but very challenging step in understanding when, how, and where planets form. PDS 70 is a young pre-main sequence star surrounded by a transition disk, in the gap of which a planetary-mass companion has recently been discovered. This discovery represents the first robust direct detection of such a young planet, possibly still at the stage of formation. Aims. We aim to characterize the orbital and atmospheric properties of PDS 70 b, which was first identified on May 2015 in the course of the SHINE survey with SPHERE, the extreme adaptive-optics instrument at the VLT. Methods. We obtained new deep SPHERE/IRDIS imaging and SPHERE/IFS spectroscopic observations of PDS 70 b. The astrometric baseline now covers 6 yr, which allowed us to perform an orbital analysis. For the first time, we present spectrophotometry of the young planet which covers almost the entire near-infrared range (0.96–3.8 μm). We use different atmospheric models covering a large parameter space in temperature, log g, chemical composition, and cloud properties to characterize the properties of the atmosphere of PDS 70 b. Results. PDS 70 b is most likely orbiting the star on a circular and disk coplanar orbit at ~22 au inside the gap of the disk. We find a range of models that can describe the spectrophotometric data reasonably well in the temperature range 1000–1600 K and log g no larger than 3.5 dex. The planet radius covers a relatively large range between 1.4 and 3.7 RJ with the larger radii being higher than expected from planet evolution models for the age of the planet of 5.4 Myr. Conclusions. This study provides a comprehensive data set on the orbital motion of PDS 70 b, indicating a circular orbit and a motion coplanar with the disk. The first detailed spectral energy distribution of PDS 70 b indicates a temperature typical of young giant planets. The detailed atmospheric analysis indicates that a circumplanetary disk may contribute to the total planetflux.

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Visible AO Observations at Halpha for Accreting Young Planets

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313007734 ◽

2013 ◽

Vol 8 (S299) ◽

pp. 32-33

Author(s):

L.M. Close ◽

K. Follette ◽

J.R. Males ◽

K. Morzinski ◽

T.J. Rodigas ◽

...

Keyword(s):

Adaptive Optics ◽

Binary Stars ◽

Optical Resolution ◽

Ccd Camera ◽

Short Exposure ◽

Low Mass ◽

Orion Trapezium ◽

First Time ◽

Adaptive Optics System ◽

Very High

AbstractWe utilized the new high-order (250-378 mode) Magellan Adaptive Optics system (MagAO) to obtain very high-resolution science in the visible with MagAO's VisAO CCD camera. In the good-median seeing conditions of Magellan (0.5–0.7″) we find MagAO delivers individual short exposure images as good as 19 mas optical resolution. Due to telescope vibrations, long exposure (60s) r' (0.63μm) images are slightly coarser at FWHM = 23-29 mas (Strehl ~ 28%) with bright (R < 9 mag) guide stars. These are the highest resolution filled-aperture images published to date. Images of the young (~ 1 Myr) Orion Trapezium θ1 Ori A, B, and C cluster members were obtained with VisAO. In particular, the 32 mas binary θ1 Ori C1C2 was easily resolved in non-interferometric images for the first time. Relative positions of the bright trapezium binary stars were measured with ~ 0.6–5 mas accuracy. In the second commissioning run we were able to correct 378 modes and achieved good contrasts (Strehl>20% on young transition disks at Hα). We discuss the contrasts achieved at Hα and the possibility of detecting low mass (~ 1–5 Mjup) planets (past 5AU) with our new SAPPHIRES survey with MagAO at Hα.

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Binary asteroid (31) Euphrosyne: ice-rich and nearly spherical

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038372 ◽

2020 ◽

Vol 641 ◽

pp. A80

Author(s):

B. Yang ◽

J. Hanuš ◽

B. Carry ◽

P. Vernazza ◽

M. Brož ◽

...

Keyword(s):

Adaptive Optics ◽

Family Formation ◽

Large Fraction ◽

Imaging Study ◽

Spherical Shape ◽

Hydrostatic Equilibrium ◽

Main Belt ◽

Binary Asteroid ◽

Water Ice ◽

The Impact

Aims. Asteroid (31) Euphrosyne is one of the biggest objects in the asteroid main belt and it is also the largest member of its namesake family. The Euphrosyne family occupies a highly inclined region in the outer main belt and contains a remarkably large number of members, which is interpreted as an outcome of a disruptive cratering event. Methods. The goals of this adaptive-optics imaging study are threefold: to characterize the shape of Euphrosyne, to constrain its density, and to search for the large craters that may be associated with the family formation event. Results. We obtained disk-resolved images of Euphrosyne using SPHERE/ZIMPOL at the ESO 8.2 m VLT as part of our large program (ID: 199.C-0074, PI: Vernazza). We reconstructed its 3D shape via the ADAM shape modeling algorithm based on the SPHERE images and the available light curves of this asteroid. We analyzed the dynamics of the satellite with the Genoid meta-heuristic algorithm. Finally, we studied the shape of Euphrosyne using hydrostatic equilibrium models. Conclusions. Our SPHERE observations show that Euphrosyne has a nearly spherical shape with the sphericity index of 0.9888 and its surface lacks large impact craters. Euphrosyne’s diameter is 268 ± 6 km, making it one of the top ten largest main belt asteroids. We detected a satellite of Euphrosyne – S/2019 (31) 1 – that is about 4 km across, on a circular orbit. The mass determined from the orbit of the satellite together with the volume computed from the shape model imply a density of 1665 ± 242 kg m−3, suggesting that Euphrosyne probably contains a large fraction of water ice in its interior. We find that the spherical shape of Euphrosyne is a result of the reaccumulation process following the impact, as in the case of (10) Hygiea. However, our shape analysis reveals that, contrary to Hygiea, the axis ratios of Euphrosyne significantly differ from those suggested by fluid hydrostatic equilibrium following reaccumulation.

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