335 Roberta rotation curves
Observations: 30 Sept, 9 Oct 2005
Michel Bonnardeau
16 Oct 2005
Updated: 26 Oct 2005
Abstract
Light/rotation curves for this asteroid are presented.
Introduction
(335) Roberta is an asteroid with an orbital period of 3.9yr, and an absolute magnitude (a magnitude at 1 au from the Sun and 1 au from Earth) of 8.96, suggesting a size of about 40 km. It has a spin period of 12.035 hours.
The orbit computed from
JPL.
Observations
The observations were carried out with a 203mm SC telescope, a Clear filter and a SBIG ST7E camera (KAF401E CCD). Each exposure is 1mn long. 365 images were obtained.
For the Sept 30 session, the comparison star is GSC 43-00612 with an assumed unfiltered magnitude of 10.500. The check star is GSC 43-00852 with a measured magnitude of 11.824 and a standard deviation of 0.012. 132 images were obtained.
For the Oct 9 session, the comparison star is GSC 40-00516 with an assumed unfiltered magnitude of 12.500. The check star is GSC 43-01098 with a measured magnitude of 12.850 and a standard deviation of 0.021. 233 images were obtained.
Red: the light curve for Roberta; Blue: for the check star, shifted by +0.3 magnitude.
The error bars are +/- the 1-sigma statistical uncertainties.
The magnitudes for the check star are shifted by -0.85 mag.
Roberta being a bright object, the exposures are only 1mn long, so as not to saturate.
To reduce the statistical uncertainties, the measurements may be stacked
(by 4):
Phase plot
The magnitudes are folded with the spin period. The period being almost
exactly 12 hours, the same phases are observed during the 2 sessions:
Between the 2 sessions, the light time of travel varies by about 8 seconds,
and the "light phase" (how the asteroid is lighted as seen from Earth)
varies from 0.992 to 0.997. The difference of magnitudes between the 2
sessions comes only from the different comparison stars.
Technical notes
Telescope and camera configuration.
Computer and software configuration.
The magnitudes are computed with the AstroMB version 2.6t software which
allows the apertures to move with the minor planet.
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