- ID:
- ivo://CDS.VizieR/J/ApJ/883/L21
- Title:
- LC of the TNO Varuna
- Short Name:
- J/ApJ/883/L21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From CCD observations carried out with different telescopes, we present short-term photometric measurements of the large trans-Neptunian object Varuna in 10 epochs, spanning around 19 years. We observe that the amplitude of the rotational light curve has changed considerably during this period of time from 0.41 to 0.55mag. In order to explain this variation, we constructed a model in which Varuna has a simple triaxial shape, assuming that the main effect comes from the change of the aspect angle as seen from Earth, due to Varuna's orbital motion in the 19yr time span. The best fits to the data correspond to a family of solutions with axial ratios b/a between 0.56 and 0.60. This constrains the pole orientation in two different ranges of solutions presented here as maps. Apart from the remarkable variation of the amplitude, we have detected changes in the overall shape of the rotational light curve over shorter timescales. After the analysis of the periodogram of the residuals to a 6.343572hr double-peaked rotational light-curve fit, we find a clear additional periodicity. We propose that these changes in the rotational light-curve shape are due to a large and close-in satellite whose rotation induces the additional periodicity. The peak-to-valley amplitude of this oscillation is in the order of 0.04mag. We estimate that the satellite orbits Varuna with a period of 11.9819hr (or 23.9638hr), assuming that the satellite is tidally locked, at a distance of ~1300km (or ~2000km) from Varuna, outside the Roche limit.
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- ID:
- ivo://CDS.VizieR/J/AJ/159/27
- Title:
- LCs of the Manwe-Thorondor eclipsing system
- Short Name:
- J/AJ/159/27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Kuiper Belt Object (385446) Manwe-Thorondor is a multiobject system with mutual events predicted to occur from 2014 to 2019. To detect the events, we observed the system at 4 epochs (UT 2016 August 25 and 26, 2017 July 22 and 25, 2017 November 9, and 2018 October 6) in g, r, and VR bands using the 4m SOAR and the 8.1m Gemini South telescopes at Cerro Pachon, Chile, and Lowell Observatory's 4.3m Discovery Channel Telescope at Happy Jack, Arizona. These dates overlap the uncertainty range (±0.5 day) for four inferior events (Thorondor eclipsing Manwe). We clearly observe variability for the unresolved system with a double-peaked period 11.88190±0.00005hr and ∼0.5mag amplitude together with much longer-term variability. Using a multicomponent model, we simultaneously fit our observations and earlier photometry measured separately for Manwe and Thorondor with the Hubble Space Telescope. Our fit suggests Manwe is bilobed, close to the "barbell" shape expected for a strengthless body with density ∼0.8g/cm<SUP>3</SUP> in hydrostatic equilibrium. For Manwe, we thereby derive maximum width to length ratio ∼0.30, surface area equivalent to a sphere of diameter 190km, geometric albedo 0.06, mass 1.4x1018kg, and spin axis oriented ∼75deg from Earth's line of sight. Changes in Thorondor's brightness by ∼0.6mag with a ∼300day period may account for the system's long-term variability. Mutual events with unexpectedly shallow depth and short duration may account for residuals to the fit. The system is complex, providing a challenging puzzle for future modeling efforts.
- ID:
- ivo://CDS.VizieR/J/ApJ/748/L25
- Title:
- Li-Be-B measurements using SIMS
- Short Name:
- J/ApJ/748/L25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Beryllium-10 is a short-lived radionuclide (t_1/2_=1.4Myr) uniquely synthesized by spallation reactions and inferred to have been present when the solar system's oldest solids (calcium-aluminum-rich inclusions, CAIs) formed. Yet, the astrophysical site of ^10^Be nucleosynthesis is uncertain. We report Li-Be-B isotope measurements of CAIs from CV chondrites, including CAIs that formed with the canonical ^26^Al/^27^Al ratio of ~5x10^-5^ (canonical CAIs) and CAIs with Fractionation and Unidentified Nuclear isotope effects (FUN-CAIs) characterized by ^26^Al/^27^Al ratios much lower than the canonical value. Our measurements demonstrate the presence of four distinct fossil ^10^Be/^9^Be isochrons, lower in the FUN-CAIs than in the canonical CAIs, and variable within these classes. Given that FUN-CAI precursors escaped evaporation-recondensation prior to evaporative melting, we suggest that the ^10^Be/^9^Be ratio recorded by FUN-CAIs represents a baseline level present in presolar material inherited from the protosolar molecular cloud, generated via enhanced trapping of galactic cosmic rays. The higher and possibly variable apparent ^10^Be/^9^Be ratios of canonical CAIs reflect additional spallogenesis, either in the gaseous CAI-forming reservoir, or in the inclusions themselves: this indicates at least two nucleosynthetic sources of ^10^Be in the early solar system. The most promising locale for ^10^Be synthesis is close to the proto-Sun during its early mass-accreting stages, as these are thought to coincide with periods of intense particle irradiation occurring on timescales significantly shorter than the formation interval of canonical CAIs.
- ID:
- ivo://CDS.VizieR/J/A+A/576/A18
- Title:
- Light curve of (2060) Chiron
- Short Name:
- J/A+A/576/A18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We propose that several short-duration events observed in past stellar occultations by Chiron were produced by ring material. Some similarities between these events and the characteristics of Chariklo's rings could indicate common mechanisms around centaurs. From a reanalysis of the stellar occultation data in the literature, we determined two possible orientations of the pole of Chiron's rings, with ecliptic coordinates {lambda}=(352+/-10){deg}, {beta}=(37+/-10){deg} or {lambda}=(144+/-10){deg}, {beta}=(24+/-10){deg}. The mean radius of the rings is (324+/-10)km. One can use the rotational lightcurve amplitude of Chiron at different epochs to distinguish between the two solutions for the pole. Both solutions imply a lower lightcurve amplitude in 2013 than in 1988, when the rotational lightcurve was first determined. We derived Chiron's rotational lightcurve in 2013 from observations at the 1.23m CAHA telescope, and indeed its amplitude was smaller than in 1988. We also present a rotational lightcurve in 2000 from images taken at the CASLEO 2.15m telescope that is consistent with our predictions. Out of the two poles, the {lambda}=(144+/-10){deg}, {beta}=(24+/-10){deg} solution provides a better match to a compilation of rotational lightcurve amplitudes from the literature and those presented here. We also show that using this preferred pole orientation, Chiron's long-term brightness variations are compatible with a simple model that incorporates the changing brightness of the rings while the tilt angle with respect to the Earth is changing with time. Also, the variability of the water ice band in Chiron's spectra as seen in the literature can be explained to a large degree by an icy ring system whose tilt angle changes with time and whose composition includes water ice, analogously to the case of Chariklo. We present several possible formation scenarios for the rings from qualitative points of view and speculate on why rings might be common in centaurs. We also speculate on whether the known bimodal color distribution of the centaurs could be due to centaurs with rings and centaurs without rings.
- ID:
- ivo://CDS.VizieR/J/A+A/546/A72
- Title:
- Light curves of Flora region asteroids
- Short Name:
- J/A+A/546/A72
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent studies have uncovered evidence that the statistical properties of asteroids' physical parameters are a fundamental source of information on the physics of their collisions and evolution. The analysis of the spin rates and spin vector distributions helps us to understand the role of various known and new effects. The alignment of spin vectors and the correlation of spin rates are for the first time observed for ten members of the Koronis family. These unexpected non-random orientations of the spin axes and correlations of the spin rates, now known as Slivan states are interpreted in terms of a YORP effect and spin-orbit resonances. To study non-gravitational-effects, there appears to be a need for new observational campaigns devoted to determining the physical parameters of the asteroid families. We analysed the photometric observations of the asteroids, which are the most efficient method of studying asteroid physical parameters.
- ID:
- ivo://CDS.VizieR/J/A+A/550/L11
- Title:
- Lightcurves of Near-Earth Asteroid 162173 (1999 JU3)
- Short Name:
- J/A+A/550/L11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Near-Earth asteroid (hereafter NEA) 162173 (1999 JU3) is a potential target of two asteroid sample return missions not only because of its accessibility but also because of the first C-type asteroid for exploration missions. The lightcurve related physical properties of this object were investigated during the 2011-2012 apparition. We aim to confirm the physical parameters useful for JAXAs Hayabusa 2 mission such as rotational period, absolute magnitude and phase function. Our data complement previous studies which did not cover low phase angles. With optical imagers and 1-2m class telescopes, we acquired the photometric data at different phase angles. We independently derived the rotational lightcurve and the phase curve of the asteroid.
- ID:
- ivo://CDS.VizieR/J/A+A/619/A123
- Title:
- Lightcurves of Near-Earth Asteroid 3200 Phaethon
- Short Name:
- J/A+A/619/A123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The near-Earth asteroid 3200 Phaethon (1983 TB) is an attractive object not only from a scientific viewpoint but also because of JAXA's DESTINY+ target. The rotational lightcurve and spin properties were investigated based on the data obtained in the ground-based observation campaign of Phaethon. We aim to refine the lightcurves and shape model of Phaethon using all available lightcurve datasets obtained via optical observation, as well as our time-series observation data from the 2017 apparition. Using eight 1-2-m telescopes and an optical imager, we acquired the optical lightcurves and derived the spin parameters of Phaethon. We applied the lightcurve inversion method and SAGE (Shaping Asteroids with Genetic Evolution) algorithm to deduce the convex and non-convex shape model and pole orientations.
- ID:
- ivo://CDS.VizieR/J/A+A/511/A49
- Title:
- Lightcurves of 12 NEAs
- Short Name:
- J/A+A/511/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Very small asteroids (VSAs) are thought to be the building blocks of larger asteroids and, as such, are interesting to study. Many of these monolithic or deeply fractured objects display rapid rotations with periods as short as several minutes. Observations of such asteroids can reveal their spin limits, which can be related to the tensile strength of their interiors. The evolution of the spins of these objects is primarily shaped by the YORP effect, the theory of which needs comparison with observations. With the 10m SALT telescope, we observed VSAs belonging to near-Earth asteroids. The obtained lightcurves were used to derive synodical periods of rotation, amplitudes, and elongations of these bodies. Results for 14 rapidly rotating asteroids were reported in the first paper in this series. Here we show lightcurves of 2 fast rotators, 9 objects with periods >=1h, and a possible non-principal axis rotator. We also list negative detections that most probably indicate asteroids with long periods and/or low amplitudes. Combining our results with the data from the literature, we obtain a set of 79 near-Earth VSAs with a median period of 0.25h (15min). By adjusting the spin limits predicted by theory to those observations, we find tentative evidence that the tensile strengths of VSAs, after scaling them to the same size, are of the same order as the minimum tensile strengths of stony meteoroids that undergo fragmentation under the atmospheric load.
- ID:
- ivo://CDS.VizieR/J/A+A/509/A94
- Title:
- Lightcurves of 14 NEAs
- Short Name:
- J/A+A/509/A94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report first results from our extensive survey of the very small (H>21.5mag) near-Earth asteroids. Our aim was to obtain photometric lightcurves for these faint, fast moving objects and to measure their rotation periods and amplitudes of light variations. These parameters can be used to make statistical analysis of the still little known population of the smallest asteroids, test present theories of the YORP effect as well as to study their spin limits, which are connected with their internal structure. Due to the faintness of the targets and the expected short periods of rotation, observations were performed with the large, 10-m SALT telescope in SAAO (South Africa). For most asteroids, V filter images with exposure times of 5-60 seconds were obtained with the instrument's SALTICAM's CCD camera. Even though the non-sidereal tracking was not available, the SALTICAM's relatively large field-of-view of 8'x8' helped to perform the relative photometry of the fast-moving targets. The presented asteroids have synodic periods ranging from 77s to 44min, effective diameters from 21 to 94m, and significantly elongated shapes.
- ID:
- ivo://CDS.VizieR/J/A+A/633/A80
- Title:
- 122 long-period comets non-gravitational param.
- Short Name:
- J/A+A/633/A80
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The original 1/a-distribution is the only observational basis for the origin of long-period comets (LPCs) and the dynamical properties of the Oort Cloud. Although they are very subtle in the motion of these comets, non-gravitational effects can cause major changes in the original semimajor axis, 1/a_ori_ We obtained reliable non-gravitational orbits for as many LPCs with small perihelion distances of q<3.1au as possible, and determined the corresponding shape of the Oort spike. We determined the osculating orbits of each comet using several data-processing methods, and selected the preferred orbit using a few specific criteria. The distribution of 1/a_ori_ for the whole comet sample was constructed using the individual Gaussian distribution we obtained for the preferred solution of each comet. The derived distribution of 1/a_ori_ for almost all known small-perihelion Oort spike comets was based on 64% of the non-gravitational orbits. This was compared with the distribution based on purely gravitational orbits, as well as with 1/a_ori_ constructed earlier for LPCs with q>3.1 au. We present a statistical analysis of the magnitudes of the non-gravitational acceleration for about 100~LPCs. The 1/a_ori_-distribution, which is based mainly on the non-gravitational orbits of small-perihelion Oort spike comets, is shifted by about 10x10^-6^au^-1^ to higher values of 1/a_ori_ compared with the distribution that is obtained when the non-gravitational effects on comet motion are ignored. We show the differences in the 1/a_ori_-distributions between LPCs with q<3.1au and those with q>3.1au. These findings indicate the important role of non-gravitational~acceleration in the motion and origin of LPCs and in the formation of the Oort Cloud.
