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TwitterDOI: 10.1051/0004-6361/200912696
Datura family: the 2009 update
D. Vokrouhlický1, J. Ďurech1, T. Michałowski2, Yu. N. Krugly3, N. M. Gaftonyuk4, A. Kryszczyńska2, F. Colas5, J. Lecacheux6, I. Molotov7, I. Slyusarev3, M. Polińska2, D. Nesvorný8, and E. Beshore91 Institute of Astronomy, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 18000 Prague 8, Czech Republic
e-mail: vokrouhl@cesnet.cz; durech@sirrah.troja.mff.cuni.cz
2 Astronomical Observatory, Adam Mickiewicz University, Słoneczna 36, 60-286 Poznań, Poland
3 Institute of Astronomy, Karazin Kharkiv National University, Sumska 35, Kharkiv 61022, Ukraine
4 Crimean Astrophysical Observatory, Simeiz Department, Simeiz 98680, Ukraine
5 IMCCE-CNRS-Observatoire de Paris, 77 avenue Denfert Rochereau, 75014 Paris, France
6 LESIA-Observatoire de Paris, 77 avenue Denfert Rochereau, 75014 Paris, France
7 Keldysh Institute of Applied Mathematics, RAS, Miusskaya 4, Moscow 125047, Russia
8 Southwest Research Institute, 1050 Walnut St, Suite 300, Boulder, CO 80302, USA
9 Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85719, USA
Received 15 June 2009 / Accepted 15 July 2009
Abstract
Context. Research of asteroid families has been recently refreshed by the discovery of
very young ones. These families are of great interest because they
represent the product of their parent body fragmentation before
orbital and physical evolutionary processes can change them. A cluster
of seven objects around the largest body (1270) Datura is of particular
interest because it has enough known members and resides in the inner part
of the main asteroid belt, facilitating observations.
Aims. We carried out photometric observations of the two largest members of
the Datura family – asteroids (1270) Datura and (90265) 2003 CL5 –
with the goal of inferring their physical parameters.
We also used numerous astrometric observations of Datura-family
members in the past few years to revisit the age of this cluster.
Methods. We performed numerous photometric observations of (1270) Datura over
several oppositions. We then used the lightcurve inversion method to
determine the spin state and shape of this asteroid. In the case of (90265)
2003 CL5, for which only limited lightcurve data have been acquired so
far, we used Fourier analysis to
determine the synodic rotation period during the 2008 apparition. We also
used backward numerical integration of the improved orbits of Datura
family members to reduce uncertainty in its age.
Results. We determined the rotation state of (1270) Datura, the largest member of
its own family. Its major properties are a short rotation period of
~3.36 h and small obliquity, which, however, exhibits ~
15° excursions because of
a forced Cassini state of the proper nodal frequency. Any possible
initial non-principal rotation state has probably been damped and the
asteroid rotates about the shortest axis of the inertia tensor. Its
global shape, although convex in our representation, may reflect regions related
to the excavation of the family members from the parent body surface.
Interestingly, the second largest member of the Datura family – (90265)
2003 CL5 – appears to be very slow rotator with the rotation period
~24 h. The large amplitude of its rotation curve suggests that its
shape is extremely elongated, possibly bi-lobed. Improved orbits of the family
members allow us to re-determine the possible age of this family. We find an
age that is slightly older than previously reported. Using a conservative
approach, we obtain an age in the 450 to 600 kyr range. With
strengthened, but plausible, conditions, we find that the current data may
support an age of 53020 kyr. Further astrometric and photometric
observations of the Datura cluster members are needed to determine its
age more accurately.
Key words: minor planets, asteroids -- techniques: photometric
© ESO 2009