- ID:
- ivo://CDS.VizieR/J/A+A/529/A86
- Title:
- Polarimetric survey of main-belt asteroids
- Short Name:
- J/A+A/529/A86
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results of a polarimetric survey of main-belt asteroids at Complejo Astronomico El Leoncito (Casleo), San Juan, Argentina. The aims of this survey are to increase the database of asteroid polarimetry, to estimate diversity in polarimetric properties of asteroids that belong to different taxonomic classes, and to search for objects that exhibit anomalous polarimetric properties, similar to those shown by the asteroid (234) Barbara. The data were obtained with the Torino and CASPROF polarimeters at the 2.15m telescope. The Torino polarimeter is an instrument that allows the simultaneous measurement of polarization in five different bands, and the CASPROF polarimeter is a two-hole aperture polarimeter with rapid modulation.
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- ID:
- ivo://CDS.VizieR/J/ApJ/864/L33
- Title:
- Polarimetric survey of Phaethon with PICO
- Short Name:
- J/ApJ/864/L33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As a function of the solar phase angle, {alpha}, the linear polarization degree (referred to the scattering plane, P_r_) of solar system objects is a good diagnostic for understanding the scattering properties of their surface materials. We report the P_r_ of Phaethon over a wide range of {alpha} from 19.1{deg} to 114.3{deg}. The derived phase-polarization curve shows that the maximum of P_r_, Pmax, is >42.4% at {alpha}>114.3{deg}, a value significantly larger than those of the moderate albedo asteroids (Pmax~9%). The phase-polarization curve classifies Phaethon as B-type as well as M- and K-type asteroids, in the polarimetric taxonomy, being compatible with the spectral property. We compute the geometric albedo, p_v_, of 0.14+/-0.04 independently by using an empirical slope-albedo relation, and the derived p_v_ is consistent with previous results determined from mid-infrared spectra and thermophysical modeling. We find no periodic variation of P_r_ in our polarimetric data in the range from 0 up to 7.208hr (e.g., less than twice the rotational period). We also find significant differences between our P_r_ during the 2017 approach toward Earth and that in 2016, implying that Phaethon has a region with different properties for light scattering near its rotational pole.
- ID:
- ivo://CDS.VizieR/J/A+A/626/A42
- Title:
- Polarimetry of Main-Belt Asteroids
- Short Name:
- J/A+A/626/A42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a polarimetric survey of main-belt asteroids at Complejo Astronomico El Leoncito (CASLEO), San Juan, Argentina. The aims of this survey are to increase the database of asteroid polarimetry and to estimate the diversity in the polarimetric properties of asteroids. The survey began in 1995 and a second period began in 2013 using the CASPOL polarimeter with a more sensitive detector to study small asteroids, families, and special taxonomic groups. The data were obtained using this instrument at the 2.15 m telescope of CASLEO. We present 128 observations for 82 asteroids of different taxonomic types. These results revealed phase-polarization curves and polarimetric parameters for 20 asteroids, amounting to a total of 135 objects with sufficient good data in the Catalogue of Asteroid Polarization Curves. Using the values obtained for the objects with a taxonomic classification, we obtained the mean polarimetric parameters for 19 taxonomic types and the Barbarians. The asteroids with large mean scatter separation distances have a minimum of the phase-polarization curve greater than -1%, slopes at the inversion angle of less than 0.12-0.15% per degree, and perihelion distances 1.8<q<2.5 au; these measurements indicate the asteroids could have high or moderate albedos and that they are objects with perihelia in the inner asteroid belt. These large mean scatter separation distance values could be the result of an electrostatic mechanism acting on the small grains of the regolith, a manifestation of a coherent backscattering mechanism, or the result of a surface formed by a mixture of dark and bright particles.
- ID:
- ivo://CDS.VizieR/J/AJ/161/237
- Title:
- Positions of Triton with Sheshan Station telescope
- Short Name:
- J/AJ/161/237
- Date:
- 20 Jan 2022
- Publisher:
- CDS
- Description:
- The large time span and precise observational data of natural satellites is of great significance for updating their ephemerides and studying their dynamic characteristics. With the help of the new image-processing methods and the Gaia DR2 catalog, all CCD images of Triton taken with the 1.56m telescope of Shanghai Astronomical Observatory during 2005-2009 were reanalyzed. The median filtering algorithm is used for image preprocessing to remove the influence of the halo of Neptune, and an upgraded modified moment, called the intensity-square-weighted centroiding method, is applied to determine the centroids of the stars and Triton. A total of 2299 positions of Triton were obtained, including 263 new observed positions and 2036 updated observed positions. Such five-year time span data with high precision will be very helpful to improve the orbit parameters of Triton.
- ID:
- ivo://CDS.VizieR/J/MNRAS/458/1117
- Title:
- Possible Ceres asteroid paleo-family
- Short Name:
- J/MNRAS/458/1117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Ceres is the largest and most massive body in the asteroid main belt. Observational data from the Dawn spacecraft reveal the presence of at least two impact craters about 280km in diameter on the Ceres surface, that could have expelled a significant number of fragments. Yet, standard techniques for identifying dynamical asteroid families have not detected any Ceres family. In this work, we argue that linear secular resonances with Ceres deplete the population of objects near Ceres. Also, because of the high escape velocity from Ceres, family members are expected to be very dispersed, with a considerable fraction of km-sized fragments that should be able to reach the pristine region of the main belt, the area between the 5J:-2A and 7J:-3A mean-motion resonances, where the observed number of asteroids is low. Rather than looking for possible Ceres family members near Ceres, here we propose to search in the pristine region.
- ID:
- ivo://CDS.VizieR/J/A+A/561/A37
- Title:
- Prediction of stellar occultations 2012.5-2014
- Short Name:
- J/A+A/561/A37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The prediction tables of stellar occultations by 5 Centaurs and 34 TNOs (referred simply as TNOs hereafter) for the period 2012.5-2014 were built to support the investigation of the physical properties of (8405) Asbolus, (24835) 1995 SM55, (10199) Chariklo, (26375) 1999 DE9, (47171) 1999 TC36, (38628) Huya, (54598) Bienor, (55565) 2002 AW197, (55576) Amycus, (83982) Crantor, (119951) 2002 KX14, (307261) 2002 MS4, (84522) 2002 TC302, (55637) 2002 UX25, (55638) 2002 VE95, (119979) 2002 WC19, (120132) 2003 FY128, (174567) 2003 MW12, (120178) 2003 OP32, 2003 UZ413, (84922) 2003 VS2, (90568) 2004 GV9, 2004 NT33, (175113) 2004 PF115, (120347) Salacia, (120348) 2004 TY364, (144897) 2004 UX10, 2005 CC79 (2011 FX62), (303775) 2005 QU182, (145451) 2005 RM43, (145452) 2005 RN43, (145453) 2005 RR43, (202421) 2005 UQ513, 2007 JH43, (278361) 2007 JJ43, (225088) 2007 OR10, (229762) 2007 UK126, 2008 OG19, and 2010 EK139 for this period. These objects are important to understand the structure, origin, and evolution of the outer solar system. Our goal was to derive precise predictions. With this aim, we constructed astrometric star catalogues in the UCAC4 system covering their sky paths. For that, we carried out during 2011-2013 an observational program at the ESO2p2/WFI instrument covering the sky path of these 39 TNOs for the period 2012.5-2014. We made the astrometry of 550 GB of images with the Platform for Reduction of Astronomical Images Automatically (PRAIA). By relatively simple astrometric techniques, we treated the overlapping observations and derived a field distortion pattern for the WFI mosaic of CCDs to within 50mas precision. The catalogue star positions were obtained in the UCAC4 frame with uncertainties of 40mas for stars up to magnitude completeness (about R=19). New stellar proper motions were also determined with 2MASS and the USNO B1.0 catalogue positions as first epoch. The catalogues for all TNOs contain in all more than 12.4 million entries, covering the sky paths of the objects with 30 arcmin width. The magnitude completeness is about R=19 with a limit about R=21. Ephemeris offsets with about 10mas to 100mas precision were applied for each TNO orbit to improve the predictions. They were obtained during 2011-2013 from a parallel observational campaign carried out with telescope diameters from 0.6m to 2.2m. The 7343 candidate stars listed in the prediction tables were searched using a proximity radius of 650mas with the geocentric apparent orbit (corrected by ephemeris offsets) of the body considered. This radius is a little more than seven times the apparent radius of a body with Pluto's size (50mas) plus the apparent Earth radius (285 mas) as projected in the sky plane at 31AU (about the Pluto-Earth distance for 2008-2015). No threshold in R magnitude was used in the search for candidates, as relatively faint R objects may turn out to be bright infrared stars, perfect targets for the SOFIA observatory and for ground-based instruments well equipped with J, H, or K band detectors (J, H, and K magnitudes are promptly available in the tables if the star belongs to the 2MASS). Besides, events may be also favoured by slow shadow speeds of less than 20km/s. Also, no constraint on a geographic place was applied, as in principle SOFIA observations can be done from any sub-solar point on Earth. Events in daylight at sub-planet point were not excluded either, as they could yet be observable in the dark, right above the horizon, from places near the Earth terminator. We furnish here prediction tables for future and also for past stellar occultations covering the sky paths between 2012.5-2014. The importance of predictions for occultations still to come is obvious. But the predictions of past occultations are also useful for at least three reasons. First, they can be used by anyone as reference for ongoing fittings of light curves of recent past observed events. Second, they serve to derive ephemeris drifts by comparing expected and observed central instants and C/A values. Finally, they can be used as an external check for the accuracy and precision of our prediction tables. In all, for R=19 stars (catalogue magnitude completeness) and 40mas errors in the WFI positions, we may assume a bulk error of about 80mas for C/A, dominated by the ephemeris offsets errors of about 70mas. For about 40AU, this implies a shadow path uncertainty over the Earth of the order of 2300km. If the ephemeris offsets can be well determined to within 30mas precision, then a bulk error of 50mas in C/A can be achieved, leading to a precision of about 1400km for the WFI occultation path predictions. Thus, the probability of actually observing the occultation is not as high as hoped, but not despairingly small, especially if the event occurs above a dense, populated region in terms of astronomers, including amateurs, with access to telescopes.
- ID:
- ivo://CDS.VizieR/J/A+A/541/A142
- Title:
- Prediction of stellar occultations 2008-2015
- Short Name:
- J/A+A/541/A142
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The prediction tables of stellar occultations by Eris, Haumea, Makemake, Quaoar, Orcus, Sedna, Varuna, Ixion, 2002TX300 and 2003AZ84 for 2008-2015 were built to support the investigation of the physical properties of large transneptunian objects - keystones in the study of structure, origin and evolution of the Solar System. Our goal was to derive precise, astrometric predictions. With this aim, we constructed astrometric star catalogs in the UCAC2 system covering their sky paths. For that, we have carried out in 2007-2009 an observational program at the ESO2p2/WFI instrument covering the sky path of these 10 large TNOs for the 2008-2015. We made the astrometry of 316 GB of images with the Platform for Reduction of Astronomical Images Automatically (PRAIA). By relatively simple astrometric techniques, we treated the overlapping observations and derived a field distortion pattern for the WFI mosaic of CCDs to within 50 mas precision. The catalog star positions were obtained in the UCAC2 frame with errors of 40mas for stars up to magnitude completeness (about R=19). New stellar proper motions were also determined with 2MASS and the USNO B1.0 catalog positions as first epoch. The catalogs of all TNOs contain in all more than 5.35 million stars with proper motions, covering the sky paths of the objects with 30 arcmin width. The magnitude completeness is about R=19 with a limit about R=21. Ephemeris offsets with about 50mas to 100mas precision were applied for each TNO orbit to improve the predictions. They were obtained during 2007-2010 from a parallel observational campaign carried out with 0.6m to 2.2m size telescopes. The 2718 candidate stars listed in the prediction tables were searched using a proximity radius of 335mas with the geocentric apparent orbit (corrected by ephemeris offsets) of the body considered. This radius is about the apparent radius of a body with Pluto's size (50mas) plus the apparent Earth radius (285mas) as projected in the sky plane at 31AU (about the Pluto-Earth distance for 2008-2015). No threshold in R magnitude was used in the search for candidates, as relatively faint R objects may turn out to be bright infrared stars, perfect targets for the SOFIA observatory and for ground-based instruments well equipped with H, J or K band detectors (H, J and K magnitudes are promptly available in the tables if the star belongs to the 2MASS). Besides, events may be also favored by slow shadow speeds of less than 20km/s. Also, no constraint on a geographic place was applied, as in principle SOFIA observations can be done from any sub-solar point on Earth. Events in daylight at sub-planet point were not excluded either, as they could yet be observable in the dark, right above the horizon, from places near the Earth terminator. We furnish here prediction tables for future and also for past stellar occultations covering the sky paths between 2008-2015. The importance of predictions for occultations still to come is obvious. But the predictions of past occultations are also useful for at least three reasons. First, they can be used by anyone as reference for ongoing fittings of light curves of recent past observed events. Second, they serve to derive ephemeris drifts by comparing expected and observed central instants and C/A values. Finally, they can be used as an external check for the accuracy and precision of our prediction tables. In all, for R=19 stars (catalog magnitude completeness) and 40mas errors in the WFI positions, we may assume a bulk error of about 80mas for C/A, dominated by the ephemeris offsets errors of about 70mas. For about 40AU, this implies a shadow path uncertainty over the Earth of the order of 2300km. If the ephemeris offsets can be well determined to within 30mas precision, then a bulk error of 50mas in C/A can be achieved, leading to a precision of about 1400km for the WFI occultation path predictions. Thus, the probability of actually observing the occultation is not as high as hoped, but not despairingly small, especially if the event occurs above a dense, populated region in terms of astronomers, including amateurs.
- ID:
- ivo://CDS.VizieR/J/ApJ/789/151
- Title:
- Properties of asteroids in comet-like orbits
- Short Name:
- J/ApJ/789/151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigated the population of asteroids in comet-like orbits using available asteroid size and albedo catalogs of data taken with the Infrared Astronomical Satellite, AKARI, and the Wide-field Infrared Survey Explorer on the basis of their orbital properties (i.e., the Tisserand parameter with respect to Jupiter, T_J_, and the aphelion distance, Q). We found that (1) there are 123 asteroids in comet-like orbits by our criteria (i.e., Q > 4.5 AU and T_J_< 3), (2) 80% of them have low albedo, p_v_< 0.1, consistent with comet nuclei, (3) the low-albedo objects among them have a size distribution shallower than that of active comet nuclei, that is, the power index of the cumulative size distribution is around 1.1, and (4) unexpectedly, a considerable number (i.e., 25 by our criteria) of asteroids in comet-like orbits have high albedo, p_v_> 0.1. We noticed that such high-albedo objects mostly consist of small (D < 3 km) bodies distributed in near-Earth space (with perihelion distance of q < 1.3 AU). We suggest that such high-albedo, small objects were susceptible to the Yarkovsky effect and drifted into comet-like orbits via chaotic resonances with planets.
- ID:
- ivo://CDS.VizieR/J/AJ/151/164
- Title:
- Properties of asteroids in Karin cluster
- Short Name:
- J/AJ/151/164
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Karin cluster is a young asteroid family thought to have formed only ~5.75Myr ago. The young age can be demonstrated by numerically integrating the orbits of Karin cluster members backward in time and showing the convergence of the perihelion and nodal longitudes (as well as other orbital elements). Previous work has pointed out that the convergence is not ideal if the backward integration only accounts for the gravitational perturbations from the solar system planets. It improves when the thermal radiation force known as the Yarkovsky effect is accounted for. This argument can be used to estimate the spin obliquities of the Karin cluster members. Here we take advantage of the fast growing membership of the Karin cluster and show that the obliquity distribution of diameter D~1-2km Karin asteroids is bimodal, as expected if the YORP effect acted to move obliquities toward extreme values (0{deg} or 180{deg}). The measured magnitude of the effect is consistent with the standard YORP model. The surface thermal conductivity is inferred to be 0.07-0.2W/m/K (thermal inertia ~300--500J/m^2^/K/s^1/2^). We find that the strength of the YORP effect is roughly ~0.7 of the nominal strength obtained for a collection of random Gaussian spheroids. These results are consistent with a surface composed of rough, rocky regolith. The obliquity values predicted here for 480 members of the Karin cluster can be validated by the light-curve inversion method.
- ID:
- ivo://CDS.VizieR/J/A+A/654/A87
- Title:
- Properties of slowly rotating asteroids.
- Short Name:
- J/A+A/654/A87
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Recent results for asteroid rotation periods from the TESS mission showed how strongly previous studies have underestimated the number of slow rotators, revealing the importance of studying those targets. For most slowly rotating asteroids (those with P>12h), no spin and shape model is available because of observation selection effects. This hampers determination of their thermal parameters and accurate sizes. Also, it is still unclear whether signatures of different surface material properties can be seen in thermal inertia determined from mid-infrared thermal flux fitting. We continue our campaign in minimising selection effects among main belt asteroids. Our targets are slow rotators with low light-curve amplitudes. Our goal is to provide their scaled spin and shape models together with thermal inertia, albedo, and surface roughness to complete the statistics. Rich multi-apparition datasets of dense light curves are supplemented with data from Kepler and TESS spacecrafts. In addition to data in the visible range, we also use thermal data from infrared space observatories (mainly IRAS, Akari and WISE) in a combined optimisation process using the Convex Inversion Thermophysical Model. This novel method has so far been applied to only a few targets, and therefore in this work we further validate the method itself. We present the models of 16 slow rotators, including two updated models. All provide good fits to both thermal and visible data.The obtained sizes are on average accurate at the 5% precision level, with diameters found to be in the range from 25 to 145km. The rotation periods of our targets range from 11 to 59h, and the thermal inertia covers a wide range of values, from 2 to <400J/m^2^/s^1/2^/K, not showing any correlation with the period. With this work we increase the sample of slow rotators with reliable spin and shape models and known thermal inertia by 40%. The thermal inertia values of our sample do not display a previously suggested increasing trend with rotation period, which might be due to their small skin depth.
