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31. Chariklo's system from stellar occultations
ID:
ivo://CDS.VizieR/J/A+A/652/A141
Title:
Chariklo's system from stellar occultations
Short Name:
J/A+A/652/A141
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Centaur (10199) Chariklo has the first rings system discovered around a small object. It was first observed using stellar occultation in 2013. Stellar occultations allow the determination of sizes and shapes with kilometre accuracy and obtain characteristics of the occulting object and its vicinity. Using stellar occultations observed between 2017 and 2020, we aim at constraining Chariklo's and its rings physical parameters. We also determine the rings' structure, and obtain precise astrometrical positions of Chariklo. We predicted and organised several observational campaigns of stellar occultations by Chariklo. Occultation light curves were measured from the data sets, from which ingress and egress times, and rings' width and opacity were obtained. These measurements, combined with results from previous works, allow us to obtain significant constraints on Chariklo's shape and rings' structure. We characterise Chariklo's ring system (C1R and C2R), and obtain radii and pole orientations that are consistent with, but more accurate than, results from previous occultations. We confirmed the detection of W-shaped structures within C1R and an evident variation of radial width. The observed width ranges between 4.8 and 9.1km with a mean value of 6.5km. One dual observation (visible and red) does not reveal any differences in the C1R opacity profiles, indicating ring particle's size larger than a few microns. The C1R ring eccentricity is found to be smaller than 0.022 (3-sigma), and its width variations may indicate an eccentricity higher than 0.005. We fit a tri-axial shape to Chariklo's detections over eleven occultations and determine that Chariklo is consistent with an ellipsoid with semi-axes of 143.8, 135.2 and 99.1km. Ultimately, we provided seven astrometric positions at a milliarcseconds accuracy level, based on Gaia EDR3, and use it to improve Chariklo's ephemeris.
32. Close encounters to the Sun in Gaia DR1
ID:
ivo://CDS.VizieR/J/A+A/609/A8
Title:
Close encounters to the Sun in Gaia DR1
Short Name:
J/A+A/609/A8
Date:
21 Oct 2021
Publisher:
CDS
Description:
I report on close encounters of stars to the Sun found in the first Gaia data release (GDR1). Combining Gaia astrometry with radial velocities of around 320 000 stars drawn from various catalogues, I integrate orbits in a Galactic potential to identify those stars which pass within a few parsecs. Such encounters could influence the solar system, for example through gravitational perturbations of the Oort cloud. 16 stars are found to come within 2pc (although a few of these have dubious data). This is fewer than were found in a similar study based on Hipparcos data, even though the present study has many more candidates. This is partly because I reject stars with large radial velocity uncertainties (>10km/s), and partly because of missing stars in GDR1 (especially at the bright end). The closest encounter found is Gl 710, a K dwarf long-known to come close to the Sun in about 1.3Myr. The Gaia astrometry predict a much closer passage than pre-Gaia estimates, however: just 16000AU (90% confidence interval: 10000-21000AU), which will bring this star well within the Oort cloud. Using a simple model for the spatial, velocity, and luminosity distributions of stars, together with an approximation of the observational selection function, I model the incompleteness of this Gaia-based search as a function of the time and distance of closest approach. Applying this to a subset of the observed encounters (excluding duplicates and stars with implausibly large velocities), I estimate the rate of stellar encounters within 5pc averaged over the past and future 5Myr to be 545+/-59Myr^-1^. Assuming a quadratic scaling of the rate within some encounter distance (which my model predicts), this corresponds to 87+/-9Myr-1 within 2pc. A more accurate analysis and assessment will be possible with future Gaia data releases.
33. Close encounters to the Sun in Gaia DR2
ID:
ivo://CDS.VizieR/J/A+A/616/A37
Title:
Close encounters to the Sun in Gaia DR2
Short Name:
J/A+A/616/A37
Date:
21 Oct 2021
Publisher:
CDS
Description:
Passing stars may play an important role in the evolution of our solar system. We search for close stellar encounters to the Sun among all 7.2 million stars in Gaia DR2 that have six-dimensional phase space data. We characterize encounters by integrating their orbits through a Galactic potential and propagating the correlated uncertainties via a Monte Carlo resampling. After filtering to remove spurious data, we find 694 stars that have median (over uncertainties) closest encounter distances within 5pc, all occurring within 15Myr from now. 26 of these have at least a 50% chance of coming closer than 1pc (and 7 within 0.5pc), all but one of which are newly discovered here. We confirm some and refute several other previously-identified encounters, confirming suspicions about their data. The closest encounter in the sample is Gl 710, which has a 95% probability of coming closer than 0.08pc (17000AU). Taking mass estimates obtained from Gaia astrometry and multiband photometry for essentially all encounters, we find that Gl 710 also has the largest impulse on the Oort cloud. Using a Galaxy model, we compute the completeness of the Gaia DR2 encountering sample as a function of perihelion time and distance. Only 15% of encounters within 5pc occurring within +/-5Myr of now have been identified, mostly due to the lack of radial velocities for faint and/or cool stars. Accounting for the incompleteness, we infer the present rate of encounters within 1pc to be 19.7+/-2.2 per Myr, a quantity expected to scale quadratically with the encounter distance out to at least several pc. Spuriously large parallaxes in our sample from imperfect filtering would tend to inflate both the number of encounters found and this inferred rate. The magnitude of this effect is hard to quantify.
34. Close star encounters
ID:
ivo://CDS.VizieR/J/A+A/575/A35
Title:
Close star encounters
Short Name:
J/A+A/575/A35
Date:
21 Oct 2021
Publisher:
CDS
Description:
Stars which pass close to the Sun can perturb the Oort cloud, injecting comets into the inner solar system where they may collide with the Earth. Using van Leeuwen's re-reduction of the Hipparcos data complemented by the original Hipparcos and Tycho-2 catalogues, along with recent radial velocity surveys, I integrate the orbits of over 50000 stars through the Galaxy to look for close encounters. The search uses a Monte Carlo sampling of the covariance of the data in order to properly characterize the uncertainties in the times, distances, and speeds of the encounters.
35. 18-cm OH lines in comets
ID:
ivo://CDS.VizieR/J/A+A/393/1053
Title:
18-cm OH lines in comets
Short Name:
J/A+A/393/1053
Date:
21 Oct 2021
Publisher:
CDS
Description:
Since the apparition of comet Kohoutek 1973 XII, the 18-cm lines of the OH radical have been systematically observed in a number of comets with the Nancay radio telescope. Between 1973 and 1999, 52 comets have been successfully detected. This allowed an evaluation of the cometary water production rates and their evolution with time, as well as a study of several physical processes such as the excitation mechanisms of the OH radio lines, the expansion of cometary atmospheres, their anisotropy in relation to non-gravitational forces, and the Zeeman effect in relation to the cometary magnetic field. Part of these observations and their analysis have already been published. The bulk of the results are now organized in a data base. The present paper is a general presentation of the Nancay cometary data base and a more specific description of the observations of 53 cometary apparitions between 1982 and 1999. Comets observed before 1982 are only partly incorporated in the data base. Observations of comets since 2000 have benefited from a major upgrade of the telescope; they will be presented in forthcoming publications.
36. Cold Classical TNOs: LCs & rotational properties
ID:
ivo://CDS.VizieR/J/AJ/157/228
Title:
Cold Classical TNOs: LCs & rotational properties
Short Name:
J/AJ/157/228
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a survey of the rotational and physical properties of the dynamically low inclination Cold Classical (CC) trans-Neptunian objects (TNOs). The CCs are primordial planetesimals and contain information about our solar system and planet formation over the first 100 million years after the Sun's formation. We obtained partial/complete light curves for 42 CCs. We use statistical tests to derive general properties about the shape and rotational frequency distributions of the CCs and infer that they have slower rotations and are more elongated/deformed than the other TNOs. On the basis of the full light curves, the mean rotational period of the CCs is 9.48+/-1.53 hr compared to 8.45+/-0.58 hr for the rest of the TNOs. About 65% of the TNOs have a light-curve amplitude below 0.2 mag compared to the 36% of CCs with small amplitude. We present the full light curve of one likely contact binary, 2004 VC_131_, with a potential density of 1 g/cm^3^ for a mass ratio of 0.4. We have hints that 2004 MU_8_ and 2004 VU_75_ are perhaps potential contact binaries, on the basis of their sparse light curves, but more data are needed to confirm this finding. Assuming equal-sized binaries, we find that ~10%-25% of the CCs could be contact binaries, suggesting a deficit of contact binaries in this population compared to previous estimates and to the (~40%-50%) possible contact binaries in the Plutino population. These estimates are lower limits and may increase if nonequal-sized contact binaries are considered. Finally, we put in context the results of the New Horizons flyby of 2014 MU_69_.
37. 6 cold-gas-bearing debris-disc stars spectra
ID:
ivo://CDS.VizieR/J/A+A/614/A3
Title:
6 cold-gas-bearing debris-disc stars spectra
Short Name:
J/A+A/614/A3
Date:
21 Oct 2021
Publisher:
CDS
Description:
Debris discs have often been described as gas-poor discs as the gas-to-dust ratio is expected to be considerably lower than in primordial, protoplanetary discs. However, recent observations have confirmed the presence of a non-negligible amount of cold gas in the circumstellar (CS) debris discs around young main-sequence stars. This cold gas has been suggested to be related to the outgassing of planetesimals and cometary-like objects. The goal of this paper is to investigate the presence of hot gas in the immediate surroundings of the cold-gas-bearing debris-disc central stars. High-resolution optical spectra of all currently known cold-gas-bearing debris-disc systems, with the exception of beta Pic and Fomalhaut, have been obtained from La Palma (Spain), La Silla (Chile), and La Luz (Mexico) observatories. To verify the presence of hot gas around the sample of stars, we have analysed the CaII H&K and the NaI D lines searching for non-photospheric absorptions of CS origin, usually attributed to cometary-like activity.
38. Colors of minor bodies in outer solar system
ID:
ivo://CDS.VizieR/J/A+A/546/A115
Title:
Colors of minor bodies in outer solar system
Short Name:
J/A+A/546/A115
Date:
21 Oct 2021
Publisher:
CDS
Description:
Photometric colours of Minor Bodies in the Outer Solar System (MBOSS). This compilation is based on over 2000 measurement epoch extracted from over 100 articles, and is fairly complete as of Dec. 2011. The average colours and additional information are available in the first file. The second file lists the code of the references used for each object. The third file lists the actual references in bibTex format. The methods used to select the data and compute the averages are described in the accompanying paper. The updated lists are available online at http://www.eso.org/~ohainaut/MBOSS Average photometric colours of Minor Bodies in the Outer Solar System. The table also lists their physico-dynamical class, the number of measurement epochs included in the average, the absolute R-band magnitude R(1,1,{alpha}), and the slope of the spectroscopic gradient (in %/100nm). are presented in table2.dat. For each MBOSS from table2.dat, table3.dat list of the references from which photometric measurements were used. The table also lists the number of measurement epochs included in the average.
39. Colors of Minor Bodies in the Outer Solar System
ID:
ivo://CDS.VizieR/J/A+A/389/641
Title:
Colors of Minor Bodies in the Outer Solar System
Short Name:
J/A+A/389/641
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a compilation of all available colors for 104 Minor Bodies in the Outer Solar System (MBOSSes); for each object, the original references are listed. The measurements were combined in a way that does not introduce rotational color artifacts. We then derive the slope, or reddening gradient, of the low resolution reflectance spectra obtained from the broad-band color for each object. A set of color-color diagrams, histograms and cumulative probability functions are presented as a reference for further studies, and are discussed.
40. Col-OSSOS: Properties of outer solar system objects
ID:
ivo://CDS.VizieR/J/AJ/157/94
Title:
Col-OSSOS: Properties of outer solar system objects
Short Name:
J/AJ/157/94
Date:
21 Oct 2021
Publisher:
CDS
Description:
Both physical and dynamical properties must be considered to constrain the origins of the dynamically excited distant solar system populations. We present high-precision (g-r) colors for 25 small (H_r_>5) dynamically excited trans-Neptunian objects (TNOs) and centaurs acquired as part of the Colours of the Outer Solar System Origins Survey. We combine our data set with previously published measurements and consider a set of 229 colors of outer solar system objects on dynamically excited orbits. The overall color distribution is bimodal and can be decomposed into two distinct classes, termed gray and red, that each has a normal color distribution. The two color classes have different inclination distributions: red objects have lower inclinations than the gray ones. This trend holds for all dynamically excited TNO populations. Even in the worst-case scenario, biases in the discovery surveys cannot account for this trend; it is intrinsic to the TNO population. Considering that TNOs are the precursors of centaurs, and that their inclinations are roughly preserved as they become centaurs, our finding solves the conundrum of centaurs being the only outer solar system population identified so far to exhibit this property. The different orbital distributions of the gray and red dynamically excited TNOs provide strong evidence that their colors are due to different formation locations in a disk of planetesimals with a compositional gradient.