1998 KY26

Orbit:

Apollo
q = 0.98 AU
a = 1.23 AU
i = 1 deg

Abs. magnitude:

H = 25.5

Rotation period, amplitude:

P = 10.70 min, ampl. 0.3

Details on photometric observations from Ondrejov:

Lightcurves in clear filter have been obtained during 1998 June 1.977-2.040 and June 2.875-3.037. The synodic rotation period (10.702 +/- 0.003) min was derived from the observations. The composite lightcurve is presented here. Although it still contains a considerable noise due to asteroid's faintness and short integration times used, the period is detected without any doubt. (See also below a figure showing the dependence of the sum of square residuals of the best fit 2nd-order Fourier series to the lightcurve points on the period.)

The lightcurve shows two maximum/minimum pairs per period, thus it looks like a normal asteroidal rotational lightcurve. Our interpretation of the period as being the rotation period of the object is in agreement with the radar results by Ostro et al. (IAUC 6935). The period is by about one order less than the shortest rotational periods of asteroids observed up to now. The quite fast rotation indicates that the object is a monolithic body. A body composed of pieces held together by self-gravitation only (the so-called 'rubble pile' structure; cf. Harris 1996, Lunar Planet. Sci. 27, 493) would require an unrealistic bulk density of more than 340 g/cm^3.

The following figure shows a dependence of the sum of square residuals of the best fit 2nd order Fourier series to the lightcurve data on the period. The above mentined period as well as a half of it are detected. The longer period is probably the real period of the asteroid, as there is marginally detected also the 3rd harmonic in the composite lightcurve for the longer period.

sum of square residuals

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