Asteroid observations with the Hubble Space Telescope FGS - II. Duplicity search and size measurements for 6 asteroids

We present the results of the observations of five Main Belt asteroids and one Trojan obtained using the Fine Guidance Sensors (FGS) of the Hubble Space Telescope. For each object, estimates of the spin axis orientation, angular size and overall shape, as well as possible indications of a binary structure, are derived. This enables the computation of new physical ephemerides. While the data concerning (63) Ausonia are clearly compatible with a three-axis ellipsoidal model, other objects show more complex shapes. (15) Eunomia, (43) Ariadne and (44) Nysa could in fact be double asteroids, or highly irregular bodies. The data concerning (624) Hektor are not conclusive as to its supposed binary nature, even if they agree with the signal of a single body. The results presented here strongly support the outstanding capabilities of the FGS for asteroid measurements, provided that the observations are performed over a sufficient time interval.

[1]  P. Seidelmann.  Explanatory Supplement to the Astronomical Almanac , 2005 .

[2]  M. Lattanzi,et al.  Asteroid (216) Kleopatra - Tests of the radar-derived shape model , 2002 .

[3]  Mario G. Lattanzi,et al.  Asteroids observations with the Hubble Space Telescope FGS - I. Observing strategy, and data analysis and modeling process , 2002 .

[4]  M. Kaasalainen,et al.  Binary structures among large asteroids , 2002 .

[5]  Keith A. Holsapple,et al.  Equilibrium Configurations of Solid Cohesionless Bodies , 2001 .

[6]  P. Thomas,et al.  Analysis of the First Disk-resolved Images of Ceres from Ultraviolet Observations with the Hubble Space Telescope , 2001, astro-ph/0110258.

[7]  P. Tanga,et al.  NOTE HST/FGS Observations of the Asteroid (216) Kleopatra , 2001 .

[8]  M. Kaasalainen,et al.  Optimization Methods for Asteroid Lightcurve Inversion: I. Shape Determination , 2001 .

[9]  S. Ostro,et al.  Radar observations of asteroid 216 kleopatra , 2000, Science.

[10]  D. Tholen,et al.  Imaging Observations of Asteroids with Hubble Space Telescope , 1999 .

[11]  M. Feast,et al.  Interferometric Angular Diameters of Mira Variables with the Hubble Space Telescope , 1997, The Astrophysical Journal.

[12]  R. S. Hudson,et al.  Shape of Asteroid 4769 Castalia (1989 PB) from Inversion of Radar Images , 1994, Science.

[13]  P. Farinella,et al.  Asteroid shapes and lightcurve morphology , 1989 .

[14]  Z. Knežević,et al.  Rotation axes of asteroids: Results for 14 objects , 1984 .

[15]  M. Martino,et al.  Photoelectric analysis of asteroid 216 Kleopatra: Implications for its shape , 1983 .

[16]  P. Farinella,et al.  Triaxial equilibrium ellipsoids among the asteroids , 1981 .

[17]  S. Weidenschilling,et al.  Hektor: Nature and origin of a binary asteroid , 1980 .

[18]  W. Hartmann,et al.  The nature of Trojan asteroid 624 Hektor , 1978 .

[19]  M. Minnaert.  The reciprocity principle in lunar photometry , 1941 .