aat Acta Astrophys. Tau. Acta Astrophysica Taurica 2712-925X Kiselev Nikolai Nikolaevich, Mosсow, settlement Moskovskii, Tat'yanin Park Str., 12, Moscow, Russia. RU 25 10.31059/aat.vol3.iss1.pp12-16 Magnetism and activity of the Sun and stars – 2021 Conference proceedings Determination of QW Ser and QZ Lib parameters from optical spectra Dudnik Anastasiya Shimansky Vladislav Borisov Nikolay Sakhbullin Nail Gabdeev Maxim Kazan (Volga Region) Federal University, Kremlyovskaya str. 18, Kazan 420008, Russia Special Astrophysical Observatory RAS, Nizhnij Arkhyz 369167, Karachai-Cherkessian Republic, Russia 3 Special Astrophysical Observatory RAS, Nizhnij Arkhyz 369167, Karachai-Cherkessian Republic, Russia 3 Kazan (Volga Region) Federal University, Kremlyovskaya str. 18, Kazan 420008, Russia Tatarstan Academy of Sciences, Bauman str. 20, Kazan 420111, Russia 29 11 2021 3 1 12 16 30 10 2021 Copyright (c) Dudnik A., Shimansky V., Borisov N., Sakhbullin N., Gabdeev M. Dudnik A., Shimansky V., Borisov N., Sakhbullin N., Gabdeev M. The metadata for this submission is licensed under a Creative Commons Attribution 4.0 International License. Copyright and publishing rights for texts published in Acta Astrophysica Taurica is retained by the authors, with first publication rights granted to the journal.Texts are free to use with proper attribution and link to the licensing (Creative Commons Attribution 4.0 International).

The paper investigates a new technique for determining dwarf nova parameters based on the analysis of their optical spectra with a signal-to-noise ratio S/N ≈ 80. We have determined parameters for the QW Ser and QZ Lib systems related to the SU UMa and WZ Sge dwarf novae. Moderate resolution spectra of both systems were obtained at BTA SAO during their low state with an optically thin accretion disk and the dominance of white dwarf radiation. As a result of the model analysis of the spectra, the parameters of the accretor atmosphere of QW Ser (T eff = 23500 ± 400 K and log g = 8.36 ± 0.05 dex) and constraints on the parameters for QZ Lib (T eff = 9500 ± 300 K and log g > 8.55 dex) were found. The presence of moderate noise in the studied spectra is not shown to affect the accuracy of determining parameters. The low temperature of the white dwarf does not allow to obtain a correct estimate of its surface gravity. Based on the determined parameters of the accretor atmospheres, a complete set of QW Ser parameters and estimates of QZ Lib parameters were found. The secondary components of both systems are defined to be red dwarfs of spectral type M.

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