A 3-D Shape Model of (704) Interamnia from
Its Occultations and Lightcurves
I. Sato, M. Buie, P. D. Maley, H. Hamanowa, A. Tsuchikawa,
and D. W. Dunham.
IJAA 4, 91 (2014).
ABSTRACT
A 3-D shape model of the sixth largest of the main belt asteroids, (704)
Interamnia, is presented. The model is reproduced from its two stellar
occultation observations and six lightcurves between 1969 and 2011. The
first stellar occultation was the occultation of TYC 234500183 on 1996
December 17 observed from 13 sites in the USA. An elliptical cross section
of (344.6 ± 9.6 km) × (306.2 ± 9.1 km), for position angle P = 73.4 ±
12.5° was fitted. The lightcurve around the occultation shows that the
peak-to-peak amplitude was 0.04 mag. and the occultation phase was just
before the minimum. The second stellar occultation was the occultation
of HIP 036189 on 2003 March 23 observed from 39 sites in Japan and
Hawaii. An elliptical cross section of (349.8 ± 0.9 km) × (303.7 ± 1.7
km), for position angle P = 86.0 ± 1.1° was fitted. A companion of 8.5
mag. of the occulted star was discovered whose separation is 12 ± 2 mas
(milli-arcseconds), P = 148 ± 11°. A combined analysis of rotational
lightcurves and occultation chords can return more information than
can be obtained with either technique alone. From follow-up photometric
observations of the asteroid between 2003 and 2011, its rotation period is
determined to be 8.728967167 ± 0.00000007 hours, which is accurate enough
to fix the rotation phases at other occultation events. The derived north
pole is λ2000 = 259 ± 8°, β2000 = -50 ± 5° (retrograde rotation);
the lengths of the three principal axes are 2a = 361.8 ± 2.8 km, 2b =
324.4 ± 5.0 km, 2c = 297.3 ± 3.5 km, and the mean diameter is D =
326.8 ± 3.0 km. Supposing the mass of Interamnia as (3.5 ± 0.9) ×
10-11 solar masses, the density is then = 3.8 ± 1.0 g·cm-3.
PDF (3.5M).
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