In April 22015, a rotational lightcurve of Achaemenides was obtained from photometric observations by Daniel Coley at the Center for Solar System Studies, in collaboration with Robert Stephens and Linda French. Lightcurve analysis gave a rotation period of 53.02±0.05 hours with a brightness amplitude of 0.36 magnitude (U=3-).[8][9][a] While not being a slow rotator, Achaemenides has one of the longest periods of all larger Jupiter trojans (see table below).
The Collaborative Asteroid Lightcurve Link assumes a standard albedo for a carbonaceous asteroid of 0.057 and calculates a diameter of 44.22 kilometers based on an absolute magnitude of 10.5.[9]
100+ largest Jupiter trojans
Largest Jupiter Trojans by survey(A) (mean-diameter in kilometers; YoD: Year of Discovery)
Note: missing data was completed with figures from the JPL SBDB (query) and from the LCDB (query form) for the WISE/NEOWISE and SIMPS catalogs, respectively. These figures are given in italics. Also, listing is incomplete above #100.
^ abLightcurve plot of (5126) Achaemenides from April 2015 by Daniel Coley at the Center for Solar System Studies (U80). Quality code is 3 (lightcurve rating at CS3). Summary figures at the LCDB and CS3.