- 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.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/649/A98
- Title:
- Lightcurve inversion for 491 asteroids
- Short Name:
- J/A+A/649/A98
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We perform lightcurve inversion for 491 asteroids to retrieve phase curve parameters, rotation periods, pole longitudes and latitudes, and convex and triaxial ellipsoid shapes by using the sparse photometric observations from Gaia Data Release 2 and the dense ground-based observations from the DAMIT data base. We develop a method for the derivation of reference absolute magnitudes and phase curves from the Gaia data, allowing for comparative studies among hundreds of asteroids.
- 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/562/A48
- Title:
- Light curves of asteroid (25143) Itokawa
- Short Name:
- J/A+A/562/A48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Near-Earth asteroid (25143) Itokawa was visited by the Hayabusa spacecraft in 2005, resulting in a highly detailed shape and surface topography model. This model has led to several predictions for the expected radiative torques on this asteroid, suggesting that its spin rate should be decelerating. To detect changes in rotation rate that may be due to YORP-induced radiative torques, which in turn may be used to investigate the interior structure of the asteroid. Through an observational survey spanning 2001 to 2013 we obtained rotational lightcurve data at various times over the last five close Earth-approaches of the asteroid. We applied a polyhedron-shape-modelling technique to assess the spin-state of the asteroid and its long term evolution. We also applied a detailed thermophysical analysis to the shape model determined from the Hayabusa spacecraft. We have successfully measured an acceleration in Itokawa's spin rate of dw/dt=(3.54+/-0.38)*10^-8^rad/day^2^, equivalent to a decrease of its rotation period of ~45ms/yr. From the thermophysical analysis we find that the center-of-mass for Itokawa must be shifted by ~21m along the long-axis of the asteroid to reconcile the observed YORP strength with theory. This can be explained if Itokawa is composed of two separate bodies with very different bulk densities of 1750+/-110kg/m^3^ and 2850+/-500kg/m^3^, and was formed from the merger of two separate bodies, either in the aftermath of a catastrophic disruption of a larger differentiated body, or from the collapse of a binary system. We therefore demonstrate that an observational measurement of radiative torques, when combined with a detailed shape model, can provide insight into the interior structure of an asteroid. Futhermore, this is the first measurement of density inhomogeneity within an asteroidal body, that reveals significant internal structure variation. A specialised spacecraft is normally required for this.
- ID:
- ivo://CDS.VizieR/J/A+A/507/495
- Title:
- Light curves of Datura and 2003 CL5 asteroids
- Short Name:
- J/A+A/507/495
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Research of asteroid families has been recently refreshed by the discovery of very young ones. These families are of great interest because they represent the product of their parent body fragmentation before orbital and physical evolutionary processes can change them. A cluster of seven objects around the largest body (1270) Datura is of particular interest because it has enough known members and resides in the inner part of the main asteroid belt, facilitating observations. We carried out photometric observations of the two largest members of the Datura family - asteroids (1270) Datura and (90265) 2003 CL5 - with the goal of inferring their physical parameters. We also used numerous astrometric observations of Datura-family members in the past few years to revisit the age of this cluster.
- ID:
- ivo://CDS.VizieR/J/AJ/134/787
- Title:
- Light curves of dwarf plutonian planets
- Short Name:
- J/AJ/134/787
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- I report new time-resolved light curves and determine the rotations and phase functions of several large Kuiper Belt objects, which includes the dwarf planet Eris (2003 UB313). Three of the new sample of 10 trans-Neptunian objects display obvious short-term periodic light curves.
- 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+AS/112/125
- Title:
- Lightcurves of minor planets
- Short Name:
- J/A+AS/112/125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 81 photometric lightcurve of 36 minor planets observed in the V and B bands at the ESO 50cm telescope at La Silla (Chile). These asteroids were selected preferentially in order to improve their ecliptic longitude coverage in view of pole determinations and lightcurve inversions. We also give some first photometric observations and/or rotational period for several asteroids.
- 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.
