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Paper: Spectroscopy and Doppler tomography of BZ Ursae Majoris in quiescence
Volume: 261, The Physics of Cataclysmic Variables and Related Objects
Page: 515
Authors: Neustroev, V. V.; Medvedev, A.; Turbin, S.; Borisov, N. V.
Abstract: BZ UMa is a little-studied, very infrequently outbursting dwarf nova with mean intervals longer than 5.2 yr, whose orbital period has been determined as 97.8 minutes (Ringwald, Thorstensen, & Hamway 1994). BZ UMa was observed on January 8, 1995 using the SP-124 spectrograph of the 6-m telescope of the Special Astrophysical Observatory. A total of 39 spectra were taken in the wavelength range 3950--5000Å with a dispersion of 1.1Å channel. Individual exposure times were 200--300 s, the total duration of the observations was about 4.5 hours. The mean spectrum of BZ UMa at first sight is typical for cataclysmic variables (Fig. 1, top panel). However it is possible to detect some peculiarities. First of all we note unusual strong Balmer lines: we found equivalent widths and relative intensities for Hβ of more than 150Å and 7.5 respectively. Secondly, BZ UMa shows the triple-peaked lines profiles, which consist of the usual double-peaked profiles from an accretion disk, and of additional narrow component at the lines center (Fig. 1, bottom panel). The visibility of the latter improves from Hβ to Hε. The origin of this component is unclear. Key for understanding of nature of the emission source of the spike is the study of its radial velocities.
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