- ID:
- ivo://CDS.VizieR/J/AJ/152/70
- Title:
- Outer Solar System Origins Survey (OSSOS). I.
- Short Name:
- J/AJ/152/70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery, tracking, and detection circumstances for 85 trans-Neptunian objects (TNOs) from the first 42deg^2^ of the Outer Solar System Origins Survey. This ongoing r-band solar system survey uses the 0.9deg^2^ field of view MegaPrime camera on the 3.6m Canada-France-Hawaii Telescope. Our orbital elements for these TNOs are precise to a fractional semimajor axis uncertainty <0.1%. We achieve this precision in just two oppositions, as compared to the normal three to five oppositions, via a dense observing cadence and innovative astrometric technique. These discoveries are free of ephemeris bias, a first for large trans-Neptunian surveys. We also provide the necessary information to enable models of TNO orbital distributions to be tested against our TNO sample. We confirm the existence of a cold "kernel" of objects within the main cold classical Kuiper Belt and infer the existence of an extension of the "stirred" cold classical Kuiper Belt to at least several au beyond the 2:1 mean motion resonance with Neptune. We find that the population model of Petit et al. remains a plausible representation of the Kuiper Belt. The full survey, to be completed in 2017, will provide an exquisitely characterized sample of important resonant TNO populations, ideal for testing models of giant planet migration during the early history of the solar system.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/643/L10
- Title:
- Phoebe Spherical Harmonics decomposition
- Short Name:
- J/A+A/643/L10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Phoebe is an irregular satellite of Saturn, and its origin, from either between the orbits of the giant planets or the Kuiper Belt, is still uncertain. The extent of differentiation of its interior can potentially help inform its formation location because it is mainly determined by heat from 26-aluminium. The internal structure is reflected in the shape, assuming the body is relaxed to hydrostatic equilibrium. Although previous data analysis indicates Phoebe is close to hydrostatic equilibrium, its heavily cratered surface makes it difficult to tease out its low-order shape characteristics. This paper aims to extract Phoebe's global shape from the observations returned by the Cassini mission for comparison with uniform and stratified interior models under the assumption of hydrostatic equilibrium. The global shape is derived from fitting spherical harmonics and keeping only the low-degree harmonics that represent the shape underneath the heavily cratered surface. The hydrostatic theoretical model for shape interpretation is based on the Clairaut equation developed to the third order (although the second order is sufficient in this case). We show that Phoebe is differentiated with a mantle density between 1900 and 2400kg/m^3^. The presence of a porous surface layer further restricts the fit with the observed shape. This result confirms the earlier suggestion that Phoebe accreted with sufficient 26-aluminium to drive at least partial differentiation, favoring an origin with C-type asteroids.
- 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/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/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/545/A131
- Title:
- Photometry of 8 main belt asteroids
- Short Name:
- J/A+A/545/A131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The shapes and spin states of asteroids observed with photometric techniques can be reconstructed using the lightcurve inversion method. The resultant models can then be confirmed or exploited further by other techniques, such as adaptive optics, radar, thermal infrared, stellar occultations, or space probe imaging. During our ongoing work to increase the set of asteroids with known spin and shape parameters, there appeared a need for displaying the model plane-of-sky orientations for specific epochs to compare models from different techniques. It would also be instructive to be able to track how the complex lightcurves are produced by various asteroid shapes.
- ID:
- ivo://CDS.VizieR/J/A+A/635/A79
- Title:
- Pitch-angle distributions of solar wind
- Short Name:
- J/A+A/635/A79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Suprathermal electron pitch-angle distributions (PADs) contain substantial information about the magnetic topology of the solar wind. Their characterisation and quantification allow us to automatically identify periods showing certain characteristics. This work presents a robust automatic method for the identification and statistical study of two different types of PADs: bidirectional suprathermal electrons (BDE, often associated with closed magnetic structures) and isotropic (likely corresponding to solar-detached magnetic field lines or highly scattered electrons). Spherical harmonics were fitted to the observed suprathermal PADs of the 119-193eV energy channel of STEREO/SWEA from March 2007 to July 2014, and they were characterised using signal processing analysis in order to identify periods of isotropic and bidirectional PADs. The characterisation has been validated by comparing the results obtained here with those of previous studies. Interplanetary coronal mass ejections (ICMEs) present longer BDE periods inside the magnetic obstacles. A significant amount of BDE remain after the end of the ICME. Isotropic PADs are found in the sheath of the ICMEs, and at the post-ICME region likely due to the erosion of the magnetic field lines. Both isotropy and BDE are solar-cycle dependent. The isotropy observed by STEREO shows a nearly annual periodicity, which requires further investigation. There is also a correspondence between the number of ICMEs observed and the percentage of time showing BDE. A method to characterise PADs has been presented and applied to the automatic identification of two relevant distributions that are commonly observed in the solar wind, such as BDE and isotropy. Four catalogues (STEREO-A and STEREO-B for isotropic and BDE periods of at least 10min) based on this identification are provided for future applications.
- ID:
- ivo://CDS.VizieR/J/A+A/625/A69
- Title:
- Plage area composite series
- Short Name:
- J/A+A/625/A69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Reconstructions of past irradiance variations require suitable data on solar activity. The longest direct proxy is the sunspot number, and it has been most widely employed for this purpose. These data, however, only provide information on the surface magnetic field emerging in sunspots, while a suitable proxy of the evolution of the bright magnetic features, specifically faculae/plage and network, is missing. This information can potentially be extracted from the historical full-disc observations in the Ca II K line. We use several historical archives of full-disc Ca II K observations to derive plage areas over more than a century. Employment of different datasets allows the identification of systematic effects in the images, such as changes in instruments and procedures, as well as an assessment of the uncertainties in the results. We have analysed over 100000 historical images from eight digitised photographic archives of the Arcetri, Kodaikanal, McMath-Hulbert, Meudon, Mitaka, Mt Wilson, Schauinsland, and Wendelstein observatories, and one archive of modern observations from the Rome/PSPT. The analysed data cover the period 1893-2018. We first performed careful photometric calibration and compensation for the centre-to-limb variation, and then segmented the images to identify plage regions. This has been consistently applied to both historical and modern observations. The plage series derived from different archives are generally in good agreement with each other. However, there are also clear deviations that most likely hint at intrinsic differences in the data and their digitisation. We showed that accurate image processing significantly reduces errors in the plage area estimates. Accurate photometric calibration also allows precise plage identification on images from different archives without the need to arbitrarily adjust the segmentation parameters. Finally, by comparing the plage area series from the various records, we found the conversion laws between them. This allowed us to produce a preliminary composite of the plage areas obtained from all the datasets studied here. This is a first step towards an accurate assessment of the long-term variation of plage regions.
- ID:
- ivo://CDS.VizieR/J/A+A/639/A88
- Title:
- Plage area composite series
- Short Name:
- J/A+A/639/A88
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Studies of long-term solar activity and variability require knowledge of the past evolution of the solar surface magnetism. An important source of such information are the archives of full-disc CaII K observations performed more or less regularly at various sites since 1892. We derive the plage area evolution over the last 12 solar cycles employing data from all CaII K archives available publicly in digital form known to us, including several as yet unexplored CaII K archives. We analyse more than 290000 full-disc CaII K observations from 43 datasets spanning the period 1892-2019. All images were consistently processed with an automatic procedure that performs the photometric calibration (if needed) and the limb-darkening compensation. The processing also accounts for artefacts plaguing many of the images, including some very specific artefacts such as bright arcs found in Kyoto and Yerkes data. The employed methods have previously been tested and evaluated on synthetic data and found to be more accurate than other methods used in the literature to treat a subset of the data analysed here. We have produced a plage area time-series from each analysed dataset. We found that the differences between the plage areas derived from individual archives are mainly due to the differences in the central wavelength and the bandpass used to acquire the data at the various sites. We have empirically cross-calibrated and combined the results obtained from each dataset to produce a composite series of plage areas. "Backbone" series are used to bridge all the series together. We have also shown that the selection of the backbone series has little effect on the final plage area composite. We have quantified the uncertainty of determining the plage areas with our processing due to shifts in the central wavelength and found it to be less than 0.01 in fraction of the solar disc for the average conditions found on historical data. We also found the variable seeing conditions during the observations to slightly increase the plage areas during activity maxima. We provide the so far most complete time series of plage areas based on corrected and calibrated historical and modern CaII K images. Consistent plage areas are now available on 88% of all days from 1892 onwards and on 98% from 1907 onwards.
