Techniques d'observation spectroscopique d'astéroïdes

124 CHAPTER 7. SPECTRAL PROPERTIES OF MAIN BELT ASTEROIDS
Relative Reflectance
1.2
1.15
1.1
1.05
1
0.95
0.9
0.85
0.8
(1333) Cevenola
0.75
0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4
Wavelength [um]
(a)
Relative Reflectance
1.2
1.15
1.1
1.05
1
0.95
0.9
0.85
0.8
0.75
(1333) Cevenola
0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4
Wavelength [um]
(b)
Figure 7.3: The NIR spectra with the error-bars for (1333) Cevenola; a) obtained in March 12, 2007; b) obtained
in March 13, 2007. The spectra are normalized to 1.25 µm.
nomia family (including Cevenola) were studied spectroscopically in the visible region by
Lazzaro et al. [1999]. Based on the visible spectrum, 41 of them were classified as S-type
objects, while three asteroids exhibit flat spectra and were considered as intruders. Considering
these samples in the frame of the Bus-DeMeo taxonomy [DeMeo et al., 2009], only three
objects are re-observed in the near-infrared region.
The visible spectrum was reported by Lazzaro et al. [2004] in the framework of S 3 OS 2 survey,
and the analysis of spectral data places the asteroid into the S (S q more precisely) complex.
The Eunomia family is actually dominated by objects displaying S-type spectra.
Two NIR spectra were obtained for this asteroid (Fig. 7.3), on two consecutive nights, separated
by 24 hours. The spectrum of March 12, 2007 is the result of the combination of individual
spectra of 120 seconds each, for the total integration time of 1.4667hrs. The second
spectrum was obtained in March 13, 2007 for the total integration time of 40min. Consequently,
a S/N of 50 and 20 was estimated. The two NIR spectra are very similar. I made an average
spectrum between the two spectra of (1333) Cevenola and I merged with the visible part from
S 3 OS 2 (Fig. 7.4a).
The SMASS-MIT online tool classifies this spectrum as an Sq type in Bus-DeMeo taxonomy.
The Sq type has a wide 1-micron absorption band with evidence of a feature near 1.3 µm
like the Q-type, except the 1-micron feature is more shallow for the Sq [DeMeo et al., 2009].
Among the solutions proposed by M4AST for taxonomic classification of this spectrum are
also the Q and K types. This is due to the fact that the spectrum is not as reddened as for Sq
type in the infrared part (Fig. 7.4b ). Using the G13 taxonomy [Birlan et al., 1996a], it can
be found that this spectrum belongs to S-complex, being in the class 2 of this taxonomy. The
class 2 of G13 taxonomy includes asteroids like (7) Iris, (11) Parthenope, (26) Proserpina, (27)
Euterpe.
The taxonomic type found for this asteroid spectrum, allows the application of space weathtel-00785991,
version 1 - 7 Feb 2013