value quality siderealorsynodic author ref method 6.7600 2 Synodic Chang 2015ApJS..219...27C Lightcurve 6.7710 2 Synodic Waszczak 2015AJ....150...75W Lightcurve 6.7770 2 Synodic Waszczak 2015AJ....150...75W Lightcurve