1996PASP..108..894T

We present time-resolved spectroscopy of the dwarf-novae AR And, AM Cas, and PY Per. From velocities of H-alpha emission lines, we determine orbital periods of 0.16302 ± 0.00032 d (=3.91 h) for AR And and 0.15480 ± 0.00017 d (=3.72 h) for PY Per. Our period determination for AR And resolves a daily cycle-count ambiguity in a previous determination by Shafter, Veal, and Robinson (1995). No orbital period for PY Per has previously been published. The orbital period of Am Cas, determined here for hte first time, is constrained over a 46-night baseline to one of several precise values near 0.165 d (=3.96 h), the best of which are 0.16490 ± 0.00001 d and 0.16551 ± 0.0001 d.

For PY Per, we use a single direct CCD exposure to extend the magnitude sequence of Misselt (1996). A comparison with the Downes & Shara atlas (1993) shows that PY Per had V ∼ 19.8 when the Downes & Shara image was obtained, which is much fainter than the minimum listed in the General Catalogue of Variable Stars (Kholopov 1987).

Our averaged spectra of all appear typical for dwarf novae, except that the Fe II lambda-5169 in AR And is unusally strong and weak features at lambda-5230, lambda-5270, and labmda-5322 (which we attribute to Fe II) also appear.