1999 JM8

Orbit, abs. magnitude:

Apollo, q = 0.97 AU, a = 2.72 AU, i = 14 deg, H = 15.2

Lightcurve period, amplitude:

P = 5.7 d, ampl. 0.7 mag

Observations and analysis:

This NEA has been observed during 1999 July 3.0 - 21.9; 15 nights from Ondrejov (mostly by L. Sarounova), 2 nights by Yu. Krugly and V. Shevchenko from Kharkiv, 2 nights by S. Mottola and F. Lahulla from Calar Alto, and 1 night by M. Hicks from Table Mountain Observatory. (One more night has been taken by Yu. Krugly on 1999 Aug. 16.0 but it has not been used in the analysis because of very different geometric conditions of the August observations.) The observations revealed a long period, large amplitude lightcurve (see Fig. 1). The formal best fit period is (5.82 +/- 0.06) d, although there exists also another, less likely but still possible solution of 5.58 d. Thus we give as result the synodic period P = (5.7 +/- 0.2) d that encompasses both solutions.

The composite lightcurve constructed for the most likely period (see Fig. 2; that for the less likely period is qualitatively similar) shows three maxima/minima per cycle that is unusual but may be caused by effects of topography at the large phase angles around 100 degrees. Some lightcurve points deviate from the best fit fifth order Fourier series; that may be caused by changing viewing/illumination geometric conditions. There is no clear evidence for a non-principal axis rotation of the body though we cannot rule out one.

A formal solution for the phase parameters yields the mean, absolute magnitude H = 15.15 +/- 0.1 and G = -0.09 +/- 0.02. The systematic errors of these values can be a few times greater.

Fig. 1: Original reduced data

Each point is an average of several measurements made in quick succession. Accuracy of each point is about 0.02 mag. The slope parameter G = -0.09 has been assumed for the plots.
1999 JM8 lighcturve

Fig. 2: Composite lightcurve for the most likely period.

Points from different cycles are marked with different symbols. 1999 JM8 composite lightcurve

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