Bibcode
Duffard, R.; Melita, M.; Ortiz, J. L.; Licandro, J.; Williams, I. P.; Jones, D.
Referencia bibliográfica
European Planetary Science Congress 2008, Proceedings of the conference held 21-25 September, 2008 in Münster, Germany. Online at http://meetings.copernicus.org/epsc2008, p.801
Fecha de publicación:
9
2008
Número de citas
0
Número de citas referidas
0
Descripción
Trojan asteroids are an interesting population of minor bodies due to
their dynamical characteristics, their physical properties and that they
are relatively isolated located at the snow-line The main hypotheses
about the origin of the Jupiter Trojans assumed that they formed either
during the final stages of the planetary formation (Marzari & Scholl
1998), or during the epoch of planetary migration (Morbidelli et al.
2005), in any case more than 3.8 Gy. ago. The dynamical configuration
kept the Trojans isolated from the asteroid Main Belt throughout the
history of the Solar System. In spite of eventual interactions with
other populations of minor bodies like the Hildas, the Jupiter family
comets, and the Centaurs, their collisional evolution has been dictated
mostly by the intrapopulation collisions (Marzari et al. 1996, 1997).
Therefore, the Jupiter Trojans may be considered primordial bodies,
whose dynamical and physical properties can provide important clues
about the environment of planetary formation. The available sample of
Jupiter Trojans light-curves is small and mainly restricted to the
largest objects. According to the MPC-website (updated last in March
2006), the present sample of rotation periods and light-curve-amplitudes
of the Jupiter Trojan asteroids is composed by 25 objects with some
information about their periods and by 10 of them with only an amplitude
estimation. A survey of contact binary Trojan asteroids has been done by
Mann et al. 2007, where they have recorded more than 100 amplitudes from
sparse-sampled light-curves and very-wellresolved rotational periods.
More than 2000 Trojan asteroids have been discovered up to date, so,
there is an urgent need to enlarge the sample of intrinsic rotation
periods and accurate light-curve amplitudes and to extend it to smaller
sizes. Results and Discusions We requested 26 nights of observation in
the second semester of 2007, to begin with the survey. They were
scheduled for the following instruments: the WFC, Isaac Newton Telescope
(ING, 2.5m, 7 nights), CAHA (2.2m, 6 nights), CCD direct OSN (1.5m, 6
nights) and CCD direct, JS (CASLEO, 2.15m, 7 nights). From these
observations we have constructed the differential photometry
light-curves of 15 Trojan asteroids. Plots showing the actual light
curves and the quality assessment of our estimation of the rotational
period can be downloaded from:
http://www.df.uba.ar/users/melita/PICT07/PICT07.ht ml. See table 1 for
the main results. In figure 1 we show the known periods of the Trojan
asteroids as a function of their size. Some of these data are still of
poor quality. It remains to be confirmed the reality of the clustering
of small objects at small periods, so, there is a need to improve those
rotation rates with reliable standard photometry produced at an
instrument of larger aperture. Also, a lack of data for the biggest
objects is apparent from this figure. In figure 2 we show a plot of the
Rmagnitude amplitude variation as a function of the absolute magnitude.
Most of the objects are from the survey of contact binaries by Mann et
al. 2007. This plot seems to indicate that the extreme elongations
recorded previously are constrained to the largest objects. Our data
follows the trend of a negative slope, but given the error-bars
involved, it remains to be confirmed if smaller objects tend to be more
spherical.