We show that ‘ Oumuamua ’ s excited spin could be in a high energy LAM state , which implies that its shape could be far from the highly elongated shape found in previous studies .
CLEAN and ANOVA algorithms are used to analyze ‘ Oumuamua ’ s lightcurve using 818 observations over 29.3 days .
Two fundamental periodicities are found at frequencies ( 2.77 \pm 0.11 ) and ( 6.42 \pm 0.18 ) cycles/day , corresponding to ( 8.67 \pm 0.34 ) h and ( 3.74 \pm 0.11 ) h , respectively .
The phased data show that the lightcurve does not repeat in a simple manner , but approximately shows a double minimum at 2.77 cycles/day and a single minimum at 6.42 cycles/day .
This is characteristic of an excited spin state .
‘ Oumuamua could be spinning in either the long ( LAM ) or short ( SAM ) axis mode .
For both , the long axis precesses around the total angular momentum vector with an average period of ( 8.67 \pm 0.34 ) h. For the three LAMs we have found , the possible rotation periods around the long axis are 6.58 , 13.15 , or 54.48 h , with 54.48 h being the most likely .
‘ Oumuamua may also be nutating with respective periods of half of these values .
We have also found two possible SAM states where ‘ Oumuamua oscillates around the long axis with possible periods at 13.15 and 54.48 h , the latter as the most likely .
In this case any nutation will occur with the same periods .
Determination of the spin state , the amplitude of the nutation , the direction of the TAMV , and the average total spin period may be possible with a direct model fit to the lightcurve .
We find that ‘ Oumuamua is “ cigar-shaped ” , if close to its lowest rotational energy , and an extremely oblate spheroid if close to its highest energy state for its total angular momentum .