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We present new spectral observations using ground-based telescopes of 23 putative V-type asteroids, selected according to colour surveys in the visible from the Moving Objects Catalogue of the Sloan Digital Sky Survey and near-infrared from the Moving Objects VISTA catalogue. 10 asteroids are orbiting in the middle main belt, while five in the outer part of the main asteroid belt. For the observed asteroids, we assign a taxonomical classification and confirm the basaltic nature for 16 of them. The high-quality spectra in the UV range, obtained with the X-Shooter spectrograph at ESO, allowed the identification of the Fe2+ forbidden transition of pyroxene for 10 asteroids. This band is centred at 506.5 nm, and it is diagnostic of the Ca-content in the pyroxene form. We determined a low Fe-content composition for asteroids (2452) Lyot, (5758) Brunini, (7675) Gorizia, (9197) Endo, (22308) 1990 UO4, (36118) 1999 RE135, (66905) 1999 VC160, and (189597) 2000 WG119, and a composition more rich in Fe for asteroids (75661) 2000 AB79 and (93620) 2000 UQ70. We also present a dynamical investigation of V-type asteroids in the middle and outer main belt. The principal finding of these simulations is that the middle and outer V-types are more likely to be associated with some families, which were considered as possibly originated from the break up of a partially or totally differentiated parent body by diverse studies. This reinforces the hypothesis that the identified V-type in the region were not originated from (4) Vesta and that the number of differentiated objects in the middle and outer main belt must have been much larger than previously assumed. [ABSTRACT FROM AUTHOR]

Abstract: Here we present some preliminary results on surface variegation found on (21) Lutetia from ROSETTA-OSIRIS images acquired on 2010-07-10. The spectrophotometry obtained by means of the two cameras NAC and WAC (Narrow and Wide Angle Cameras) is consistent with ground based observations, and does not show surface diversity above the data error bars. The blue and UV images (shortward 500nm) may, however, indicate a variegation of the optical properties of the asteroid surface on the Baetica region (). We also speculate on the contribution due to different illumination and to different ground properties (composition or, more probably, grain size diversity). In particular a correlation with geologic units independently defined by is evident, suggesting that the variegation of the ground optical properties is likely to be real. [Copyright &y& Elsevier]

Abstract In the course of its last close encounter with the Earth in December 2017, the peculiar Near Earth Object (NEO) 3200 Phaethon has been the target of an international observational campaign in particular connected with the proposed mission Destiny+ (Demonstration and Experiment of Space Technology for INterplanetary voYage Phaethon fLyby dUSt science) by JAXA (Japan Aerospace Exploration Agency) to be launched in 2022. The nature of 3200 Phaethon is still debated because of its asteroidal dynamical behavior as opposed to its connection with the Geminid meteor shower, typical cometary residuals. Owing to its vicinity to our planet (Minimum Orbit Intersection Distance MOID = 0.0206 AU) it has been included also in the class of Potentially Hazardous objects and it has been extensively investigated also during its previous perihelion passages. It has been classified as B-type asteroid (Binzel et al., 2001), with different spectral slopes found by several authors in the wavelength region shortward 0.55 μ m. Many issues remain to be explored regarding the nature of this object and in this context we observed 3200 Phaethon in the course of 24 h during its last closest approach to the Earth. Low-resolution spectra at very high elevation angles (airmass < 1.15) were acquired with the 1.22–m Asiago telescope on 2017-Dec-16 and 2017-Dec-17. The variation of the viewing geometry during these observations was also derived. We found a significant variation in Phaethon spectral slope in the wavelength range [0.33–0.64] μ m during its perigeon passage. The slope varies from − 9.1 ± 0.2 % (/ 0.1 μ m) on 2017-Dec-16 to − 2.0 ± 0.1 % (/ 0.1 μ m) on 2017-Dec-17. This variation seems to be related to a disappearing bluer region at high latitudes (> 70 ∘ , close to the North pole). The spectra show also a weak absorption band around 0.43 μ m and lack the reflectance downturn at least until ∼ 0.33 μ m. The comparison with meteorites suggests compositional similarities with CI/CM unusual chondrites. We propose several scenarios that could be responsible for the variability recorded, such as possible surface variations in composition, grain-size, or the level of space weathering and thermal metamorphism. A strong and sudden variation of dust production is also discussed. Highlights • Significant variation in Phaethon spectral slope. • Observed variation seems related to the disappearing of the northern polar region. • Lack the reflectance downturn until 0.33micron. • Detection for the first time of the 0.43 μm band: Phaethon hydration? • Very good match with CI/CM meteorites. [ABSTRACT FROM AUTHOR]

The potentially hazardous asteroid (PHA) 2014 JO25 made a close approach to Earth on 19 April 2017 at the distance of 0.0118 AU, giving the opportunity to study its nature with large spatial resolution from ground-based observatories. Radar observations revealed an object with a clear bilobate shape. We aimed at the characterization of the surface properties of the object, the determination of its spectral class and the search for possible surface heterogeneities, possibly linked to the two lobes, during different rotational phases. Fourteen low-resolution spectra were acquired with the Boller & Chivens optical spectrograph mounted on the 1.22–m Asiago telescope. The spectra covered an entire rotation period of the asteroid. Data were reduced using IRAF and analyzed with the M4AST tool to infer the best fit Bus-Demeo taxonomy type. We found the asteroid belonging to the S/Q complex of silicaceous asteroids, complex comprising the vast majority of NEAs. This is the tenth bilobate NEA to be taxonomically classified and only the seventh bilobate PHA. We found no clear proof of surface heterogeneity, but there is an interestingvariation in the best spectral match which appears to be synchronous with the rotation period of the object. [ABSTRACT FROM AUTHOR]