Autori: Birlan M., Barucci M.A., Vernazza, P., Fulchignoni M., Binzel R.P., Bus S.J., Fornasier S.

Editorial: Elsevier, New Astronomy, Vol. 9 (5), p.343-351, 2004.

Rezumat:

In cadrul programului international de observatie ai asteroizilor posibili a fi survolati de sonda spatiala Rosetta, grupul nostru a efectuat observatii in mod „remote observing”, de la Meudon-Franta, cu telescopul IRTF situat in insulele Hawaii. Pe parcursul a doua perioade de observatie, in martie si iunie 2003, am utilizat spectrograful SpeX in domeniul de lungimi de unda 0.8-2.5 microni.

In aceasta lucrare sunt prezentate spectrele asteroizilor 21 Lutetia, 89 Julia, 140 Siwa, 2181 Fogelin, si 5480 (1989YK8).

Spectrele asteroizilor 21 Lutetia si 140 Siwa sunt plate si fara benzi de absorptie. In spectrul asteroidului 89 Julia se disting benzile de absorptie de la 1 si 2 microni, care pot fi interpretate ca indicatori de prezenta a mineralelor cu continut de olivina si olivina-piroxen; de obicei aceste minerale desemneaza asteroizii de tip S.

Asteroizii 2181 Fogelin si 5480(1989YK8) fac parte din categoria obiectelor de talie mica si au fost observati print tehnici spectroscopice pentru prima data. Spectrele in infrarosu paropiat indica prezenta benzii de absorptie centrata la 1 micron care poate fi interpretatta ca indicatia prezentei de minerale metamorfice/magmatice la suprafata acestor obiecte; noi observati in regiunea vizibila a spectrului ca si observatii de albedo termic sunt necesare pentru a elabora o concluzie viabila. In the frame of the international campaign to observe potential target asteroids for the Rosetta mission, remote observations have been carried out between Observatoire de Paris, in Meudon-France, and the NASA Infrared Telescope Facility on Mauna Kea. The SpeX instrument was used in the 0.8-2.5 microns spectral region, for two observing runs in March and June 2003.

This paper presents near-IR spectra of the asteroids 21 Lutetia, 89 Julia,
140 Siwa, 2181 Fogelin, and 5480 (1989YK8).

Near-IR spectra of the asteroids 21 Lutetia and 140 Siwa are flat and featureless. The spectrum of 89 Julia reveals absorption bands around 1 and 2 microns, which may indicate the presence of olivine and olivine-pyroxene mixtures and confirm the S-type designation.

The small main-belt asteroids 2181 Fogelin and 5480 (1989YK8) are investigated spectroscopically for the first time. Near-IR spectra of these asteroids also show an absorption feature around 1 micron, which could be and indicator of igneous/metamorphic surface of the objects; new observations in visible as well as thermal albedo data are necessary to draw a reliable conclusion on the surface mineralogy of both asteroids.

Cuvinte cheie: spectroscopic, asteroizi, infrarosu, sistem solar // spectroscopic, asteroids, infrared, solar system