- ID:
- ivo://CDS.VizieR/J/A+A/638/A84
- Title:
- PACS observations of large main-belt asteroids
- Short Name:
- J/A+A/638/A84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Non-resolved thermal infrared observations enable studies of thermal and physical properties of asteroid surfaces provided the shape and rotational properties of the target are well determined via thermo-physical models. We used calibration-programme Herschel PACS data (70, 100, 160 microns) 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.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/591/A14
- Title:
- PCF, SpecB or SDSSB asteroids parameters
- Short Name:
- J/A+A/591/A14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- B-type asteroids constitute a peculiar spectral class within the C-complex. Previous work has pointed out the difference between the visible geometric albedos of B-types and those of the Pallas collisional family (PCF), whose few members with observed spectra are B-types (one exception out of eight objects). This has been interpreted as being due to compositional differences. However, the PCF members are typically smaller than the spectroscopically classified B-types, and the following possibilities have not been ruled out: the albedo differences might be related to a size-albedo dependence and/or to the generally larger errors of the WISE data and best-fitting values of the derived parameters expected for smaller objects. We compare albedos and beaming parameters of PCF members and B-types of similar sizes and re-examine our conclusion on the different composition of the PCF. By modelling their WISE/NEOWISE data, we derived sizes and albedos of all objects whose Sloan Digital Sky Survey reflectances are similar to the typical B-type reflectance spectra. In particular, we derived the so-called infrared beaming parameters (eta), effective diameters (D), and corresponding visible geometric albedos (pV), and studied their value distributions.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A149
- Title:
- PHA contact-binary (85990) 1999 JV6 light curves
- Short Name:
- J/A+A/631/A149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The potentially hazardous asteroid (85990) 1999 JV6 has been a target of previously published thermal-infrared observations, and optical photometry. It has been identified as a promising candidate for possible Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect detection. The YORP effect is a small thermal-radiation torque attributed to be a key factor in spin-state evolution of small Solar System bodies. In order to detect YORP on 1999 JV6 we develop a detailed shape model and analyse the spin-state using both optical and radar observations. For 1999 JV6, we collected optical photometry between 2007 and 2016. Additionally, we obtained radar echo-power spectra and imaging observations with Arecibo and Goldstone planetary radar facilities in 2015, 2016, and 2017. We combine our data with published optical photometry to develop a robust physical model. We determine that the rotation pole resides at negative latitudes in an area with a 5{deg} radius, close to the south ecliptic pole. The refined sidereal rotation period is 6.536787+/-0.000007h. The radar images are best reproduced with a bilobed shape model. Both lobes of 1999 JV6 can be represented as oblate ellipsoids with a smaller, more spherical component resting at the end of a larger, more elongated component. While contact binaries appear to be abundant in the near-Earth population, there exists just a few published shape models for asteroids in this particular configuration. By combining the radar-derived shape model with optical light curves we determine a constant-period solution that fits all available data well. Using light curve data alone we determine an upper limit for YORP 8.5x10^-8^rad/day^2^. The bifurcated shape of 1999 JV6 might be a result of two ellipsoidal components gently merging with each other, or a deformation of a rubble pile with a weak-tensile-strength core due to spin-up. The physical model of 1999 JV6 presented here will enable future studies of contact binary asteroid formation and evolution.
- ID:
- ivo://CDS.VizieR/J/A+A/375/285
- Title:
- Photometric observations of 9 Near-Earth Objects
- Short Name:
- J/A+A/375/285
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new CCD observations of nine Near-Earth Asteroids carried out between February, 1999 and July, 2000. The bulk of the data was acquired through an R_C_ filter, while the minor planet 11405 was observed without filter. Data were obtained with the 1.23m telescope of the German-Spanish Astronomical Centre, Calar Alto; with the 0.60m telescope of the Konkoly Observatory and with the 0.28m telescope of the Szeged Observatory. We could determine synodic periods and amplitudes for 5 asteroids, 699: 3.3h, 0.18m; 1866: 2.7h, 0.12m; 1999 JD6: 7.68h, 1.2m ; 2000 GK137: 4.84h, 0.27m; 2000 NM: 9.24h, 0.30m. Based on observations taken at different phases, we could infer a phase parameter m of 0.018+/-0.005 for 1865 Cerberus. An epoch-method yielded a sideral period of 0.27024003(5) for this object with retrograde rotation. The remaining 3 objects have only partial coverage, thus no firm conclusion on their synodic period is possible.
- ID:
- ivo://CDS.VizieR/J/A+A/479/877
- Title:
- Photometric variations of Eris (136199)
- Short Name:
- J/A+A/479/877
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Eris is the largest dwarf planet currently known in the solar system. Knowled ge about its physical parameters is necessary to interpret the characteristics of these kinds of bodies. The goal of this work is to study Eris' short-term and long-term variability in order to determine the amplitude of the light-curve, which can be linked to the degree of elongation of the body or to the degree of albedo heterogeneity on the surface of the dwarf planet. In addition, the rotation period can be determined. CCD photometric observations of the trans Neptunian object Eris in R band on 16 nights spanning two years were carried out using the 1.5m telescope at Sierra Nevada Observatory (OSN), the 2.5m Isaac Newton Telescope (INT) telescope at the Roque de los Muchachos Observatory, and the 2.2m Telescope at Calar Alto Observatory. The time-series analysis leads to indications of a short-term variability whose nature is not clear. It could be real or a result of data-reduction artifacts, such as contamination by close, faint-background stars. The most significant periodicities are 14h or its double, but other possibilities cannot be ruled out, like a 32h weaker peak in the periodogram. As for the amplitude of the light-curve, we get a peak-to-peak variability of 0.01+/-0.01mag. The study of the long-term variability indicates that a long rotation period cannot be rejected, but the amplitude would be smaller than 0.06mag. These results are compatible with a nearly spherical body that has a homogeneous surface.
- ID:
- ivo://CDS.VizieR/J/A+A/610/A7
- Title:
- Photometry and models of long-period asteroids
- Short Name:
- J/A+A/610/A7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The available set of spin and shape modelled asteroids is strongly biased against slowly rotating targets and those with low lightcurve amplitudes. This is due to the observing selection effects. As a consequence, the current picture of asteroid spin axis distribution, rotation rates, radiometric properties, or aspects related to the object's internal structure might be affected too. To counteract these selection effects, we are running a photometric campaign of a large sample of main belt asteroids omitted in most previous studies. Using least chi-squared fitting we determined synodic rotation periods and verified previous determinations. When a dataset for a given target was sufficiently large and varied, we performed spin and shape modelling with two different methods to compare their performance. We used the convex inversion method and the non-convex SAGE algorithm, applied on the same datasets of dense lightcurves. Both methods search for the lowest deviations between observed and modelled lightcurves, though using different approaches. Unlike convex inversion, the SAGE method allows for the existence of valleys and indentations on the shapes based only on lightcurves. We obtain detailed spin and shape models for the first five targets of our sample: (159) Aemilia, (227) Philosophia, (329) Svea, (478) Tergeste, and (487) Venetia. When compared to stellar occultation chords, our models obtained an absolute size scale and major topographic features of the shape models were also confirmed. When applied to thermophysical modelling (TPM), they provided a very good fit to the infrared data and allowed their size, albedo, and thermal inertia to be determined. Convex and non-convex shape models provide comparable fits to lightcurves. However, some non-convex models fit notably better to stellar occultation chords and to infrared data in sophisticated thermophysical modelling (TPM). In some cases TPM showed strong preference for one of the spin and shape solutions. Also, we confirmed that slowly rotating asteroids tend to have higher-than-average values of thermal inertia, which might be caused by properties of the surface layers underlying the skin depth.
- ID:
- ivo://CDS.VizieR/J/AJ/154/241
- Title:
- Photometry of a Kuiper Belt object: 2002 CC_249_
- Short Name:
- J/AJ/154/241
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Images of the Kuiper Belt object (126719) 2002 CC_249_ obtained in 2016 and 2017 using the 6.5 m Magellan-Baade Telescope and the 4.3 m Discovery Channel Telescope are presented. A light curve with a periodicity of 11.87+/-0.01 hr and a peak-to-peak amplitude of 0.79+/-0.04 mag is reported. This high amplitude double-peaked light curve can be due to a single elongated body, but it is best explained by a contact binary system from its U-/V-shaped light curve. We present a simple full-width-at-half-maximum test that can be used to determine if an object is likely a contact binary or an elongated object based on its light curve. Considering that 2002 CC_249_ is in hydrostatic equilibrium, a system with a mass ratio q_min_=0.6, and a density {rho}_min_=1 g/cm^3^, or less plausible a system with q_max_=1, and {rho}_max_=5 g/cm^3^ can interpret the light curve. Assuming a single Jacobi ellipsoid in hydrostatic equilibrium and an equatorial view, we estimate {rho}>=0.34 g/cm^3^, and a/b=2.07. Finally, we report a new color study showing that 2002 CC_249_ displays an ultra red surface characteristic of a dynamically Cold Classical trans-Neptunian object.
- ID:
- ivo://CDS.VizieR/J/A+A/527/A42
- Title:
- Photometry of asteroid (21) Lutetia
- Short Name:
- J/A+A/527/A42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- On its journey to comet 67P/Churyumov-Gerasimenko, the International Rosetta Mission (ESA) was planned to fly-by two asteroids: (2867) Steins and (21) Lutetia. Although classified as an M-type asteroid because of its high albedo, its reflectance spectrum in the near and mid-infrared region, suggests a primitive composition, more typical of C-type asteroids. Results from ground-based observations are indicative of compositional variegation and of at least one significantly large crater on the surface of this asteroid. We analyse photometric and spectroscopic data of the asteroid, obtained from ground-based observations, to support the data taken by the spacecraft.
- ID:
- ivo://CDS.VizieR/J/A+A/551/A102
- Title:
- Photometry of 16 Flora family asteroids
- Short Name:
- J/A+A/551/A102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It is known that the Yarkovsky effect moves small asteroids to larger/smaller semimajor axes depending on their prograde/retrograde spins. The YORP effect influences asteroid spin periods and spin axis orientations so that they evolve in time. The alignment of the spin vectors and correlations of the spin rates, now known as Slivan states and observed among members of the Koronis family, are interpreted in terms of the YORP effect and spin-orbit resonances. Splitting asteroid families into prograde and retrograde groups has recently been proposed as a result of the Yarkovsky effect. Prograde and retrograde asteroids drift in different directions, and this has never been observed directly. The influence of the Yarkovsky and YORP effects should be observable among objects in asteroid families, especially in the Flora family, which lies close to the Sun and consists of many small objects. The Flora family asteroids were modelled using the lightcurve inversion technique. As a result the orientation of spin vectors, shapes, and sidereal periods of rotation were obtained.
- ID:
- ivo://CDS.VizieR/J/A+A/529/A107
- Title:
- Photometry of 4 main belt asteroids
- Short Name:
- J/A+A/529/A107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The set of more than 100 asteroids, for which spin parameters have been modelled using an amplitude, magnitude or epoch methods, showed a pronounced gap in the distribution of the asteroid spin axes. These spin axes are rarely aligned with the ecliptic plane. The number of asteroids with known spin parameters should be increased to allow for statistical investigations. We gathered extensive photometric datasets on four selected main-belt asteroids to model their spin and shape parameters using the lightcurve inversion method. Our only criterion of selection was their observability for small telescopes.
