Periodograms (in the frequency domain) of (130) Elektra based on convex inversion (left) and tri-axial ellipsoids (right). Each minimum represents one trial run sampling all the local minima at fixed rotation period. The vertical line indicates the best-fitting value (consistent with the LCDB period of 5.225 h). The horizontal line represents the χ² threshold defined by Eq. (3). There are more than 110 000 trial periods for Elektra (see Eq. (2)). The prominent side minima near P and P/2 are the aliases at ±0.5 cycles day⁻¹ around P and ±1 cycles day⁻¹ around P/2. Convex inversion models generically show more periodogram structure than the ellipsoidal models.