Spectroscopy and photometry of the dwarf nova BZ Ursae Majoris and the CV linewidth/K, mass-ratio relation

Abstract

Time resolved spectroscopy of the dwarf nova BZ UMa revelas periodic velocity variations in the hydrogen emission lines with P = 97.9 ± 0.1 minutes and K = 73 ± 6 km s-1. CCD photometry over a 16-month interval shows three outbursts of about 4 mag with a mean separation of 181 days. The mean FWHM for the H-beta emission is large, prompting a re-calibration of the FWHM/K vs. mass ratio relation, giving a mass ratio (MRD/MWD) of 0.20 for BZ UMa. The short period, long outburst interval, and small mass ratio supports the suggestion of BZ UMa being in the SU UMa subclass of dwarf novae.