- ID:
- ivo://CDS.VizieR/J/A+A/624/A121
- Title:
- Asteroid (7) Iris Deconvolved disk-resolved images
- Short Name:
- J/A+A/624/A121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Asteroid (7) Iris is an ideal target for disk-resolved imaging owing to its brightness (V~7-8) and large angular size of 0.33'' during its apparitions. Iris is believed to belong to the category of large unfragmented asteroids that avoided internal differentiation, implying that its current shape and topography may record the first few 100Myr of the solar system's collisional evolution. We recovered information about the shape and surface topography of Iris from disk-resolved VLT/SPHERE/ZIMPOL images acquired in the frame of our ESO large program. We used the All-Data Asteroid Modeling (ADAM) shape reconstruction algorithm to model the 3D shape of Iris, using optical disk-integrated data and disk-resolved images from SPHERE and earlier AO systems as inputs. We analyzed the SPHERE images and our model to infer the asteroid's global shape and the morphology of its main craters. Results. We present the 3D shape, volume-equivalent diameter D_eq_=214+/-5km, and bulk density {rho}=2.7+/-0.3g/cm^3^ of Iris. Its shape appears to be consistent with that of an oblate spheroid with a large equatorial excavation. We identified eight putative surface features 20-40km in diameter detected at several epochs, which we interpret as impact craters, and several additional crater candidates. Craters on Iris have depth-to-diameter ratios that are similar to those of analogous 10km craters on Vesta. The bulk density of Iris is consistent with that of its meteoritic analog based on spectroscopic observations, namely LL ordinary chondrites. Considering the absence of a collisional family related to Iris and the number of large craters on its surface, we suggest that its equatorial depression may be the remnant of an ancient (at least 3Gyr) impact. Iris's shape further opens the possibility that large planetesimals formed as almost perfect oblate spheroids. Finally, we attribute the difference in crater morphology between Iris and Vesta to their different surface gravities, and the absence of a substantial impact-induced regolith on Iris.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/150/75
- Title:
- Asteroid light curves from PTF survey
- Short Name:
- J/AJ/150/75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We fit 54296 sparsely sampled asteroid light curves in the Palomar Transient Factory survey to a combined rotation plus phase-function model. Each light curve consists of 20 or more observations acquired in a single opposition. Using 805 asteroids in our sample that have reference periods in the literature, we find that the reliability of our fitted periods is a complicated function of the period, amplitude, apparent magnitude, and other light-curve attributes. Using the 805-asteroid ground-truth sample, we train an automated classifier to estimate (along with manual inspection) the validity of the remaining ~53000 fitted periods. By this method we find that 9033 of our light curves (of ~8300 unique asteroids) have "reliable" periods. Subsequent consideration of asteroids with multiple light-curve fits indicates a 4% contamination in these "reliable" periods. For 3902 light curves with sufficient phase-angle coverage and either a reliable fit period or low amplitude, we examine the distribution of several phase-function parameters, none of which are bimodal though all correlate with the bond albedo and with visible-band colors. Comparing the theoretical maximal spin rate of a fluid body with our amplitude versus spin-rate distribution suggests that, if held together only by self-gravity, most asteroids are in general less dense than ~2g/cm^3^, while C types have a lower limit of between 1 and 2g/cm3. These results are in agreement with previous density estimates. For 5-20km diameters, S types rotate faster and have lower amplitudes than C types. If both populations share the same angular momentum, this may indicate the two types' differing ability to deform under rotational stress. Lastly, we compare our absolute magnitudes (and apparent-magnitude residuals) to those of the Minor Planet Center's nominal (G=0.15, rotation-neglecting) model; our phase-function plus Fourier-series fitting reduces asteroid photometric rms scatter by a factor of ~3.
1293. Asteroid masses
- ID:
- ivo://CDS.VizieR/J/AJ/112/2319
- Title:
- Asteroid masses
- Short Name:
- J/AJ/112/2319
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The orbits of 4583 main belt asteroids are integrated orbits for 57 years and searched for asteroid-asteroid encounters from which it may be possible to determine the masses of 23 of the largest asteroids (diameter>=200km) and 11 smaller asteroids. The search is conducted using a scattering formula which serves as a useful filter for identifying encounters that can lead to a mass determination. A total of 460 such encounters were found. The ten most useful of these encounters are examined in detail. The results show that, to make a reliable mass determination, the mean distance of the perturbed asteroid must be known to within a few times 10^-8^AU. An observing program targeting the asteroids listed here would have a substantial impact on our knowledge of asteroid masses and densities.
- ID:
- ivo://CDS.VizieR/J/A+A/643/A59
- Title:
- Asteroid models reconstructed from ATLAS phot.
- Short Name:
- J/A+A/643/A59
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Asteroid Terrestrial-impact Last Alert System (ATLAS) is an all-sky survey primarily aimed at detecting potentially hazardous near-Earth asteroids. Apart from the astrometry of asteroids, it also produces their photometric measurements that contain information about asteroid rotation and their shape. To increase the current number of asteroids with a known shape and spin state, we reconstructed asteroid models from ATLAS photometry that was available for approximately 180000 asteroids observed between 2015 and 2018. We made use of the light-curve inversion method implemented in the Asteroids@home project to process ATLAS photometry for roughly 100000 asteroids with more than a hundred individual brightness measurements. By scanning the period and pole parameter space, we selected those best-fit models that were, according to our setup, a unique solution for the inverse problem. We derived ~2750 unique models, 950 of them were already reconstructed from other data and published. The remaining 1800 models are new. About half of them are only partial models, with an unconstrained pole ecliptic longitude. Together with the shape and spin, we also determined for each modeled asteroid its color index from the cyan and orange filter used by the ATLAS survey. We also show the correlations between the color index, albedo, and slope of the phase-angle function. The current analysis is the first inversion of ATLAS asteroid photometry, and it is the first step in exploiting the huge scientific potential that ATLAS photometry has. ATLAS continues to observe, and in the future, this data, together with other independent photometric measurements, can be inverted to produce more refined asteroid models.
- ID:
- ivo://CDS.VizieR/VII/288
- Title:
- Asteroid phase curve coefficients from ATLAS observations
- Short Name:
- VII/288
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Asteroid phase curves are used to derive fundamental physical properties through the determination of the absolute magnitude H. The upcoming visible Legacy Survey of Space and Time (LSST) and mid-infrared Near-Earth Object Surveillance Mission (NEOSM) surveys rely on these absolute magnitudes to derive the colours and albedos of millions of asteroids. Furthermore, the shape of the phase curves reflects their surface compositions, allowing for conclusions on their taxonomy. We derive asteroid phase curves from dual-band photometry acquired by the Asteroid Terrestrial-impact Last Alert System telescopes. Using Bayesian parameter inference, we retrieve the absolute magnitudes and slope parameters of 127012 phase curves of 94777 asteroids in the photometric H, G1, G2- and H, G12*-systems. The taxonomic complexes of asteroids separate in the observed G1, G2-distributions, correlating with their mean visual albedo. This allows for differentiating the X-complex into the P-, M-, and E-complexes using the slope parameters as alternative to albedo measurements. Further, taxonomic misclassifications from spectrophotometric datasets as well as interlopers in dynamical families of asteroids reveal themselves in G1, G2-space. The H, G12*-model applied to the serendipitous observations is unable to resolve target taxonomy. The G1, G2 phase coefficients show wavelength-dependency for the majority of taxonomic complexes. Their values allow for estimating the degree of phase reddening of the spectral slope. The uncertainty of the phase coefficients and the derived absolute magnitude is dominated by the observational coverage of the opposition effect rather than the magnitude dispersion induced by the asteroids' irregular shapes and orientations. Serendipitous asteroid observations allow for reliable phase curve determination for a large number of asteroids. To ensure that the acquired absolute magnitudes are suited for colour computations, it is imperative that future surveys densely cover the opposition effects of the phase curves, minimizing the uncertainty on H. The phase curve slope parameters offer an accessible dimension for taxonomic classification, correlating with the albedo and complimentary to the spectral dimension.
- ID:
- ivo://CDS.VizieR/J/other/CoSka/33.159
- Title:
- Asteroid positions in 2002
- Short Name:
- J/other/CoSka/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The paper presents the results of position determinations of minor planets carried out at the Skalnate Pleso Observatory in the year 2002. 109 CCD observations of 21 minor planets are given together with the list of reference stars.
- ID:
- ivo://CDS.VizieR/J/other/OAP/31.235
- Title:
- 2728 asteroid positions (Kitab obs.)
- Short Name:
- J/other/OAP/31.2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photographic observations of XX century contained numerous and varied information about all objects and events of the Universe fixed on the astronegatives. The original and interesting observations of small bodies of the Solar system in previous years can be selected and used for various scientific tasks. Existing databases and online services can help make such selection easily and quickly. The observations of chronologically earlier oppositions, photometric evaluation of brightness for long periods of time allow refining the orbits of asteroids and identifying various non-stationarities. Photographic observations of the Northern Sky Survey project (FON project) were used for global search for small bodies of Solar system. About 2000 photographic plates of Kitab part of the FON project were made using Double Wide Angle Astrograph at the Kitab observatory (Uzbekistan) during 1981-1989. Early, using that digitized observations the catalogue of equatorial coordinates and stellar magnitudes for more than 13 million stars and galaxies up to B=17.5m was compiled. At present, we analyzed all processing results for the search of asteroids and compiled the catalogue of equatorial coordinates and stellar magnitudes of them. As a result more than 4500 asteroids and comets with visual magnitude from 7.7m to 17.5m were identified now. All positions of asteroids were compared with ephemeris. A preliminary analysis of O-C differences was carried out. New and interesting are that the moments of official discovery of some identified asteroids much later than their moments of Kitab's observation. In addition, some of them are the earliest observations of these asteroids in the world among all known observations. More than 915 observations of such asteroids have been found on the plates of Kitab part of the FON project.
- ID:
- ivo://CDS.VizieR/J/A+A/338/340
- Title:
- Asteroids as IR Standards for ISOPHOT
- Short Name:
- J/A+A/338/340
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Asteroids are used as far-IR calibrators for the imaging photopolarimeter ISOPHOT on board the Infrared Space Observatory ISO. For the 10 selected objects we compiled a large uniform database of 678 individual observations, ranging from 7-2000{mu}m. Applying a new thermophysical model to the observations we derived thermal properties of the selected asteroids, based on spin-vector solutions, direct size measurements and the HG-magnitude system. Our investigations indicate very rough surfaces, reflected in the beaming effect, and very low levels of heat conduction, expressed in thermal inertias between 5 and 25J/m^2^/s^0.5^/K. Due to scattering processes in the porous regolith, the emissivity varies significantly with wavelength. In case of Vesta we find emissivities as low as 0.6 in the far-IR/submillimetre region. By entering the combined results into the thermophysical model we defined new photometric standards for the far-IR. The absolute accuracy for thermal flux or lightcurve predictions is 5-10% for the first category objects and 10-20% for the secondaries. The methods and procedures discussed here are included in the first update of the ISOPHOT calibration in 1998.
- ID:
- ivo://CDS.VizieR/J/A+A/572/A29
- Title:
- Asteroids for a targeted spectroscopic survey
- Short Name:
- J/A+A/572/A29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Asteroid spectroscopy reflects surface mineralogy. There are few thousand asteroids whose surfaces have been observed spectrally. Determining the surface properties of those objects is important for many practical and scientific applications, such as for example developing impact deflection strategies or studying history and evolution of the Solar System and planet formation. The aim of this study is to develop a pre-selection method that can be utilized in searching for asteroids of any taxonomic complex. The method could then be utilized im multiple applications such as searching for the missing V-types or looking for primitive asteroids. We used the Bayes Naive Classifier combined with observations obtained in the course of the Sloan Digital Sky Survey and the Wide-field Infrared Survey Explorer surveys as well as a database of asteroid phase curves for asteroids with known taxonomic type. Using the new classification method we have selected a number of possible V-type candidates. Some of the candidates were than spectrally observed at the Nordic Optical Telescope and South African Large Telescope. We have developed and tested the new pre-selection method. We found three asteroids in the mid/outer Main Belt that are likely of differentiated type. Near-Infrared are still required to confirm this discovery. Similarly to other studies we found that V-type candidates cluster around the Vesta family and are rare in the mid-to-outer Main Belt. The new method shows that even largely explored large databases combined together could still be further exploited in for example solving the missing dunite problem.
- ID:
- ivo://CDS.VizieR/VII/108C
- Title:
- Asteroids II Machine-Readable Data Base
- Short Name:
- VII/108C
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This data set was assembled by E. F. Tedesco, Jet Propulsion Laboratory, in March 1988 from files provided by the contributors to the above reference. Included are asteroid names and discovery circumstances, proper elements and family identifications, asteroid lightcurve parameters, asteroid pole determinations, taxonomic classes, absolute magnitudes and slope parameters, UBV color indices, and albedos and diameters from the IRAS Asteroid and Comet Survey. The asteroid discovery tables were updated by F. Pilcher in 1994.
