61 research outputs found
The first confirmation of V-type asteroids among the Mars crosser population
The Mars crossing region constitutes a path to deliver asteroids from the
Inner Main Belt to the Earth crossing space. While both the Inner Main Belt and
the population of Earth crossing asteroids contains a significant fraction of
asteroids belonging to the V taxonomic class, only two of such V-type asteroids
has been detected in the Mars crossing region up to now. In this work, we
searched for asteroids belonging to the V class among the population of Mars
crossing asteroids, in order to support alternative paths to the delivery of
this bodies into the Earth crossing region. We selected 18 candidate V-type
asteroids in the Mars crossing region using observations contained in the Sloan
Digital Sky Survey Moving Objects Catalog. Then, we observed 4 of these
candidates to take their visible spectra using the Southern Astrophysical
Research Telescope (SOAR). We also performed the numerical simulation of the
orbital evolution of the observed asteroids. We confirmed that 3 of the
observed asteroids belong to the V class, and one of these may follow a path
that drives it to an Earth collision in some tens of million years
Taxonomic classification of asteroids based on MOVIS near-infrared colors
We aim to provide a taxonomic classification for asteroids observed by
VISTA-VHS survey. We derive a method for assigning a compositional type to an
object based on its (Y-J), (J-Ks), and (H-Ks) colors. We present a taxonomic
classification for 18\,265 asteroids from the MOVIS catalog, using a
probabilistic method and the k-nearest neighbors algorithm. Because our
taxonomy is based only on NIR colors, several classes from Bus-DeMeo were
clustered into groups and a slightly different notation was used (i.e. the
superscript indicates that the classification was obtained based on the NIR
colors and the subscript indicates possible miss-identifications with other
types). Our results are compared with the information provided by the Sloan
Digital Sky Survey (SDSS) and Wide-field Infrared Survey Explorer (WISE). The
two algorithms used in this study give a taxonomic type for all objects having
at least (Y-J) and (J-Ks) observed colors. A final classification is reported
for a set of 6\,496 asteroids based on the criteria that KNN and probabilistic
algorithms gave the same result, (Y-J) 0.118 and
(J-Ks)0.136. This set includes 144 bodies classified as ,
613 as , 197 as , 91 as , 440 as , 665
as , 233 as , 3\,315 as , and 798 as . We
report the albedo distribution for each taxonomic group and we compute new
median values for the main types. We found that V-type and A-type candidates
have identical size frequency distributions, but the V-types are five times
more common than the A-types. Several particular cases, such as the A-type
asteroid (11616) 1996 BQ2 and the S-type (3675) Kematsch, both in the Cybele
population, are discussed. Files and codes available at:
https://github.com/marcelpopescu/MOVIS-TaxonomyComment: 18 pages, 10 figures, accepted for publication in Astronomy &
Astrophysics (A&A
Physical properties of ESA Rosetta target asteroid (21) Lutetia: Shape and flyby geometry
Aims. We determine the physical properties (spin state and shape) of asteroid
(21) Lutetia, target of the ESA Rosetta mission, to help in preparing for
observations during the flyby on 2010 July 10 by predicting the orientation of
Lutetia as seen from Rosetta.
Methods. We use our novel KOALA inversion algorithm to determine the physical
properties of asteroids from a combination of optical lightcurves,
disk-resolved images, and stellar occultations, although the latter are not
available for (21) Lutetia.
Results. We find the spin axis of (21) Lutetia to lie within 5 degrees of
({\lambda} = 52 deg., {\beta} = -6 deg.) in Ecliptic J2000 reference frame
(equatorial {\alpha} = 52 deg., {\delta} = +12 deg.), and determine an improved
sidereal period of 8.168 270 \pm 0.000 001 h. This pole solution implies the
southern hemisphere of Lutetia will be in "seasonal" shadow at the time of the
flyby. The apparent cross-section of Lutetia is triangular as seen "pole-on"
and more rectangular as seen "equator-on". The best-fit model suggests the
presence of several concavities. The largest of these is close to the north
pole and may be associated with large impacts.Comment: 17 pages, 5 figures, 3 tables, submitted to Astronomy and
Astrophysic
Physical and dynamical characterization of hyperbolic comet C/2017 U7(PANSTARRS)
We present here a dynamical and observational study of the comet C/2017 U7 (PANSTARRS). This comet was discovered in 2017 and found to have a hyperbolic orbit. Our dynamical analysis shows that the object has probably originated in the Oort cloud, however an interstellar origin cannot be discarded. The observations were obtained in 2018 and 2019 using the Goodman High Throughput Spectrograph (GHTS) at the SOAR telescope. We obtained visible spectra covering the wavelength range of and also images in the SDSS filters system. Both the low-resolution reflectance spectrum and the reflectance spectra derived from the SDSS filters show an atypical band at . We conducted a comparative study of the colors and reflectance spectra of different small body populations (e.g., comets, Centaurs, and trans-Neptunian objects or TNOs) from the literature and concluded that the spectra and the colors of this comet are atypical, showing only some overlap with those of some known members of the TNOs and Centaurs, within the large uncertainties of the measurements of those populations. It is found that the feature and overall spectral shape can be reproduced by laboratory spectra of kerite, a template for aliphatic-rich hydrocarbons that has been previously identified in NIR cometary spectra absorptions. It is tentatively proposed that the unusual spectral shape is the result of a particle size distribution of dust grains in the coma or on the surface that has arisen due to a low grain ejection velocity from the surface and large nucleus size
J-PLUS: A first glimpse at spectrophotometry of asteroids -- The MOOJa catalog
Context: The Javalambre Photometric Local Universe Survey (J-PLUS) is an
observational campaign that aims to obtain photometry in 12 ultraviolet-visible
filters (0.3-1 {\mu}m) of approximately 8 500 deg{^2} of the sky observable
from Javalambre (Teruel, Spain). Due to its characteristics and strategy of
observation, this survey will let us analyze a great number of Solar System
small bodies, with improved spectrophotometric resolution with respect to
previous large-area photometric surveys in optical wavelengths. Aims: The main
goal of this work is to present here the first catalog of magnitudes and colors
of minor bodies of the Solar System compiled using the first data release (DR1)
of the J-PLUS observational campaign: the Moving Objects Observed from
Javalambre (MOOJa) catalog. Methods: Using the compiled photometric data we
obtained very-low-resolution reflectance (photospectra) spectra of the
asteroids. We first used a {\sigma}-clipping algorithm in order to remove
outliers and clean the data. We then devised a method to select the optimal
solar colors in the J-PLUS photometric system. These solar colors were computed
using two different approaches: on one hand, we used different spectra of the
Sun, convolved with the filter transmissions of the J-PLUS system, and on the
other, we selected a group of solar-type stars in the J-PLUS DR1, according to
their computed stellar parameters. Finally, we used the solar colors to obtain
the reflectance spectra of the asteroids. Results: We present photometric data
in the J-PLUS filters for a total of 3 122 minor bodies (3 666 before outlier
removal), and we discuss the main issues of the data, as well as some
guidelines to solve the
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