#
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.

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

Points from different cycles are marked with different symbols.

Back to the Ondrejov NEO program page.