Changes in the spectrum of Z Ursae Majoris during its rise through a maximum in June 2014

Abstract

The semiregular variable Z UMa experienced a particularly deep minimum at the end of March 2014 followed by a three month rise to maximum. The rise and subsequent decline were followed with low resolution (R~1000) spectroscopy, possibly for the first time. The spectral type of Z UMa varied between M7III at minimum and M4III at maximum while the bright hydrogen emission lines reported by observers during the last century now appear relatively weak and transitory.