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Search Results: 1 - 10 of 297511 matches for " J. Licandro "
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NICS-TNG infrared spectroscopy of trans-neptunian objects 2000 EB173 and 2000 WR106
J. Licandro,E. Oliva,M. Di MArtino
Physics , 2001, DOI: 10.1051/0004-6361:20010758
Abstract: We report complete near-infrared (0.9-2.4 $\mu$m) spectral observations of trans-neptunian objects (TNOs) 2000 EB173 and 2000 WR106 collected using the new Near Infrared Camera Spectrometer (NICS) attached to the 3.56m Telescopio Nazionale Galileo (TNG). Both spectra are very red and with a quite strong and broad drop extending throughout the K band. However, while 2000 EB173 does not show any evidence of narrow absorption features, the spectrum of 2000 WR106 has quite deep water ice absorption at 1.5 and 2.0 $\mu$m. Moreover, the latter object is significantly less red than the former indicating, therefore, that the surface of 2000 WR106 is ``cleaner'' (i.e. less processed by particle irradiation) than that of 2000 EB173.
Infrared spectroscopy of the largest known trans-neptunian object 2001 KX76
J. Licandro,F. Ghinassi,L. Testi
Physics , 2002, DOI: 10.1051/0004-6361:20020533
Abstract: We report complete near-infrared (0.9-2.4 $\mu$m) spectral observations of the largest know trans-neptunian objects (TNO) 28976 = 2001 KX$_{76}$ taken in two different nights using the new Near Infrared Camera Spectrometer (NICS) attached to the 3.56m Telescopio Nazionale Galileo (TNG). The spectra are featureless and correspond to a neutral colored object. Our observations indicate that the surface of 2001 KX$_{76}$ is probably highly evolved due to long term irradiation, and that collisional resurfacing processes have not played an important role in its evolution.
Rotationally resolved spectroscopy of dwarf planet (136472) Makemake
V. Lorenzi,N. Pinilla-Alonso,J. Licandro
Physics , 2015, DOI: 10.1051/0004-6361/201425575
Abstract: Context. Icy dwarf planets are key for studying the chemical and physical states of ices in the outer solar system. The study of secular and rotational variations gives us hints of the processes that contribute to the evolution of their surface. Aims. The aim of this work is to search for rotational variability on the surface composition of the dwarf planet (136472) Makemake Methods. We observed Makemake in April 2008 with the medium-resolution spectrograph ISIS, at the William Herschel Telescope (La Palma, Spain) and obtained a set of spectra in the 0.28 - 0.52 {\mu}m and 0.70 - 0.95 {\mu}m ranges, covering 82% of its rotational period. For the rotational analysis, we organized the spectra in four different sets corresponding to different rotational phases, and after discarding one with low signal to noise, we analyzed three of them that cover 71% of the surface. For these spectra we computed the spectral slope and compared the observed spectral bands of methane ice with reflectances of pure methane ice to search for shifts of the center of the bands, related to the presence of CH 4 /N 2 solid solution. Results. All the spectra have a red color with spectral slopes between 20%/1000 {\AA} and 32%/1000 {\AA} in accordance with previously reported values. Some variation in the spectral slope is detected, pointing to the possibility of a variation in the surface content or the particle size of the solid organic compound. The absorption bands of methane ice present a shift toward shorter wavelengths, indicating that methane (at least partially) is in solid solution with nitrogen. There is no variation within the errors of the shifts with the wavelength or with the depth of the bands, so there is no evidence of variation in the CH 4 /N 2 mixing ratio with rotation. By comparing with all the available data in the literature, no secular compositional variations between 2005 and 2008 is found.
Size and albedo distributions of asteroids in cometary orbits using WISE data
J. Licandro,V. Ali-Lagoa,G. Tancredi,Y. Fernandez
Physics , 2015, DOI: 10.1051/0004-6361/201526866
Abstract: We study the distributions of effective diameter ($D$), beaming parameter ($\eta$), and visible geometric albedo ($p_V$) of asteroids in cometry orbits (ACOs) populations, derived from NASA's Wide-field Infrared Explorer (WISE) observations, and compare these with the same, independently determined properties of the comets. The near-Earth asteroid thermal model (NEATM) is used to compute the $D$, $p_V$ and $\eta$. We obtained $D$ and $p_V$ for 49 ACOs in Jupiter family cometary orbits (JF-ACOs) and 16 ACOs in Halley-type orbits (Damocloids). We also obtained $\eta$ for 45 of them. All but three JF-ACOs (95% of the sample) present a low albedo compatible with a cometary origin. The $p_V$ and $\eta$ distributions of both ACO populations are very similar. For the entire sample of ACOs, the mean geometric albedo is $\bar{p_V} = 0.05 \pm 0.02$, ($\bar{p_V} = 0.05 \pm 0.01$ and $\bar{p_V} =0.05 \pm 0.02$ for JF-ACOs and Damocloids, respectively) compatible with a narrow albedo distribution similar to that of the Jupiter family comets (JFCs), with a $\bar{p_V} \sim 0.04$. The $\bar{\eta} =1.0 \pm 0.2$. We find no correlations between $D$, $p_V$ , or $\eta$. We compare the cumulative size distribution (CSD) of ACOs, Centaurs, and JFCs. Although the Centaur sample contains larger objects, the linear parts in their log-log plot of the CSDs presents a similar cumulative exponent ($\beta = 1.85 \pm 0.30$ and $1.76 \pm 0.35$, respectively). The CSD for Damocloids presents a much shallower exponent $\beta = 0.89 \pm 0.17$. The CSD for JF-ACOs is shallower and shifted towards larger diameters with respect to the CSD of active JFCs, which suggests that the mantling process has a size dependency whereby large comets tend to reach an inactive stage faster than small ones. Finally, the population of JF-ACOs is comparable in number that of JFCs, although there are more tens-km JF-ACOs than JFCs.
Thermophysical properties of near-Earth asteroid (341843) 2008 EV5 from WISE data
V. Alí-Lagoa,L. Lionni,M. Delbo,B. Gundlach,J. Blum,J. Licandro
Physics , 2013, DOI: 10.1051/0004-6361/201322215
Abstract: Aims. To derive the thermal inertia of 2008 EV$_5$, the baseline target for the Marco Polo-R mission proposal, and infer information about the size of the particles on its surface. Methods. Values of thermal inertia are obtained by fitting an asteroid thermophysical model to NASA's Wide-field Infrared Survey Explorer (WISE) infrared data. From the constrained thermal inertia and a model of heat conductivity that accounts for different values of the packing fraction (a measure of the degree of compaction of the regolith particles), grain size is derived. Results. We obtain an effective diameter $D = 370 \pm 6\,\mathrm{m}$, geometric visible albedo $p_V = 0.13 \pm 0.05$ (assuming $H=20.0 \pm 0.4$), and thermal inertia $\Gamma = 450 \pm 60$ J/m2/s(1/2)/K at the 1-$\sigma$ level of significance for its retrograde spin pole solution. The regolith particles radius is $r = 6.6^{+1.3}_{-1.3}$ mm for low degrees of compaction, and $r = 12.5^{+2.7}_{-2.6}$ mm for the highest packing densities.
Rotationally resolved spectroscopy of (20000) Varuna in the near-infrared
V. Lorenzi,N. Pinilla-Alonso,J. Licandro,C. M. Dalle Ore,J. P. Emery
Physics , 2014, DOI: 10.1051/0004-6361/201322251
Abstract: Models of the escape and retention of volatiles by minor icy objects exclude any presence of volatile ices on the surface of TNOs smaller than ~1000km in diameter at the typical temperature in this region of the solar system, whereas the same models show that water ice is stable on the surface of objects over a wide range of diameters. Collisions and cometary activity have been used to explain the process of surface refreshing of TNOs and Centaurs. These processes can produce surface heterogeneity that can be studied by collecting information at different rotational phases. The aims of this work are to study the surface composition of (20000)Varuna, a TNO with a diameter ~650km and to search for indications of rotational variability. We observed Varuna during two consecutive nights in January 2011 with NICS@TNG obtaining a set of spectra covering the whole rotation period of Varuna. After studying the spectra corresponding to different rotational phases, we did not find any indication of surface variability. In all the spectra, we detect an absorption at 2{\mu}m, suggesting the presence of water ice on the surface. We do not detect any other volatiles on the surface, although the S/N is not high enough to discard their presence. Based on scattering models, we present two possible compositions compatible with our set of data and discuss their implications in the frame of the collisional history of the Kuiper Belt. We find that the most probable composition for the surface of Varuna is a mixture of amorphous silicates, complex organics, and water ice. This composition is compatible with all the materials being primordial. However, our data can also be fitted by models containing up to a 10% of methane ice. For an object with the characteristics of Varuna, this volatile could not be primordial, so an event, such as an energetic impact, would be needed to explain its presence on the surface.
Discovery of a Low-Mass Brown Dwarf Companion of the Young Nearby Star G196-3
R. Rebolo,M. R. Zapatero Osorio,S. Madruga,V. J. S. Bejar,S. Arribas,J. Licandro
Physics , 1998, DOI: 10.1126/science.282.5392.1309
Abstract: A substellar-mass object in orbit at about 300 astronomical units (AU) from the young low-mass star G196-3 was detected by direct imaging. Optical and infrared photometry and low- and intermediate-resolution spectroscopy of the faint companion, hereafter referred to as G196-3B, confirms its cool atmosphere and allows its mass to be estimated at 25^{+15}_{-10} Jupiter masses. The separation between both objects and their mass ratio suggest the fragmentation of a collapsing cloud as the most likely origin for G196-3B, but alternatively it could have originated from a proto-planetary disc which has been dissipated. Whatever the formation process was, the young age of the primary star (about 100 Myr) demonstrates that substellar companions can form in short time scales.
Near-infrared spectroscopy of 1999 JU3, the target of the Hayabusa 2 mission
N. Pinilla-Alonso,V. Lorenzi,H. Campins,J. deLeon,J. Licandro
Physics , 2013, DOI: 10.1051/0004-6361/201221015
Abstract: Context. Primitive asteroids contain complex organic material and ices relevant to the origin of life on Earth. These types of asteroids are the target of several-sample return missions to be launched in the next years. 1999 JU3 is the target of the Japanese Aerospace Exploration Agency's Hayabusa 2 mission. Aims. 1999 JU3 has been previously identified as a C-class asteroid. Spectroscopic observations at longer wavelengths will help to constrain its composition. Methods. We obtained spectroscopy of 1999 JU3 from 0.85 to 2.2 microns, with the 3.6 m Telescopio Nazionale Galileo using the low resolution mode of the Near Infrared Camera Spectrograph. Results. We present a near-infrared spectrum of 1999 JU3 from 0.85 to 2.2microns that is consistent with previously published spectra and with its C-type classification. Conclusions. Our spectrum confirms the primitive nature of 1999 JU3 and its interest as target of the sample-return mission Hayabusa 2.
On the dust environment of Main-Belt Comet 313P/Gibbs
F. J. Pozuelos,A. Cabrera-Lavers,J. Licandro,F. Moreno
Physics , 2015, DOI: 10.1088/0004-637X/806/1/102
Abstract: We present observations carried out using the 10.4 m Gran Telescopio Canarias and an interpretative model of the dust environment of activated asteroid 313P/Gibbs. We discuss three different models relating to different values of the dust parameters, i.e, dust loss rate, maximum and minimum sizes of particles, power index of the size distribution, and emission pattern. The best model corresponds with an isotropic emission of particles which started on August 1st. The size of grains were in the range of $0.1-2000$ $\mu$m, with velocities for 100 $\mu$m particles between $0.4-1.9$ m$~$s$^{-1}$, with a dust production rate in the range of $0.2-0.8$ kg$~$s$^{-1}$. The dust tails' brightness and morphology are best interpreted in terms of a model of sustained and low dust emission driven by water-ice sublimation, spanning since 2014 August 1st, and triggered by a short impulsive event. This event produced an emission of small particles of about 0.1 $\mu$m with velocities of $\sim$4 m$~$s$^{-1}$. From our model we deduce that the activity of this Main-Belt Comet continued for, at least, four months, since activation.
Integrated Study of the Physical Characteristics of Primitive Solar System Bodies
L. Kolokolova,B. A. S. Gustafson,L. M. Lara,J. Licandro
Revista mexicana de astronomía y astrofísica , 2003,
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