Techniques d'observation spectroscopique d'astéroïdes

Mon. Not. R. Astron. Soc. 000, 000–000 (0000) Printed 17 March 2011 (MN LATEX style file v2.2)
Spectral properties of (854) Frostia, (1333) Cevenola, and
(3623) Chaplin ⋆
M. Birlan 1 †, D.A. Nedelcu 2 , P. Descamps 1 , J. Berthier 1 , F. Marchis 3 ,
S. Merouane 4 , and M. Popescu 1
1 Institut de Mécanique Céleste et de Calcul des Éphémérides (IMCCE),
Observatoire de Paris, 77 avenue Denfert-Rochereau, 75014 Paris Cedex, France
2 Astronomical Institute of the Romanian Academy, 5 Cuţitul de Argint, RO-040557 Bucharest, Romania
3 University of California at Berkeley, Dept. of Astronomy, 601 Campbell Hall, Berkeley, CA 94720, USA
4 University Paris VII, Dept. of Physics, 75206 Paris Cedex, France
17 March 2011
tel-00785991, version 1 - 7 Feb 2013
ABSTRACT
Near-infrared spectroscopy can play a key role for establishing the mineralogical composition
and supporting other physical data obtained by complementary observational
techniques such as adaptive optics, radar, and photometry. The objective of our survey
was asteroids which present large variations in their lightcurves. We report observations
for asteroids (854) Frostia, (1333) Cevenola, and (3623) Chaplin carried out in
the 0.8-2.5 m spectral range using SpeX/IRTF in LowRes mode. The spectral modeling
of these asteroids give new insights to these peculiar objects in the main-belt.
(854) Frostia is a V-type asteroid, and its spectral properties are similar to those of
basalts. The most probable mineralogical solution Wo 8 Fs 43 En 49 was calculated for
Frostia. (1333) Cevenola was estimated to have an S q spectral type, in agreement
with its membership to the Eunomia family. (3623) Chaplin is an S-type asteroid, in
agreement with the taxonomic type of the Koronis family.
Key words: asteroids, spectroscopy, mineralogical model
1 INTRODUCTION
The lightcurve of an asteroid is the display of the variation of
its magnitude over time. The lightcurve is related to the rotation
of an asteroid around an instantaneous axis. In other
words, the lightcuve could be interpreted as an observable
of the angular momentum for a given object. This variation
is primarily due to the shape (French & Binzel 1989). The
lightcurve could be also due to the albedo variation (Harris
& Lupishko 1989) of the asteroids. The results of observations
of lightcurves for asteroids are regularly synthesized in
catalogs of lightcurves (for example Lagerkvist et al. (1987)).
Several asteroids exhibit large amplitude lightcurves,
which remained unexplained until the last decade. Several
explanations were proposed for these variations, starting
with elongated shaped asteroids and including double and
multiple systems of aggregates in a weak self-gravitational
field (Cellino et al. 1985).
The number of known multiple systems among asteroids
has increased significantly in recent years. In the past,
⋆ The article uses observations performed with SpeX/IRTF
† E-mail:Mirel.Birlan@imcce.fr
the binarity and multiplicity of asteroids was suggested by
several authors (van Flandern et al. 1979) based on occultations
of stars (for example in the articles of Binzel
(1978) 1 , and Donnison (1979) 2 ) or photoelectric photometry
(Tedesco 1979; Binzel & van Flandern 1979; Dunlap
& Gehrels 1969). These observational facts were the origin
of theoretical problems related to spin evolution and stability
(Wijesinghe & Tedesco 1979; Zappala et al. 1980; Leone
et al. 1984).
Several articles are based on observations using various
techniques namely radar (Ostro et al. 2002, 2000; Magri
et al. 2007), adaptive optics (Marchis et al. 2005), adaptive
optics combined with lightcurve photometry (Descamps
et al. 2007), and lightcurve photometry (Behrend et al. 2006;
Pravec et al. 2002).
Analytical and numerical simulations of catastrophic
collisions among small bodies, using several hypothesis, are
published regularly by several teams (Durda et al. 2004;
1 The article also presents historical facts of occultation of stars
by asteroids.
2 This satellite was not confirmed by direct imaging. (Storrs et al.
1999)
c○ 0000 RAS