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Hα spectroscopy of the recurrent nova RS Oph during the 2021 outburst

Stoyanov, K. A.; Marchev, D.; Zamanov, R. K. +3 more

We report spectroscopic observations of the Hα emission line of the recurrent nova RS~Oph obtained between 2021 August 12 and 2021 August 23 during the recent outburst. On the basis of the sharp P~Cyg profile superimposed onto the strong Hα emission, we estimate that the outflowing velocity of the material surrounding RS~Oph is in the range 32 km …

Ultra-short period contact binaries: restricting the parameters of the primary using Gaia parallax

Kurtenkov, Alexander

Possible M-type contact binaries were investigated by selecting W UMa-type variables with orbital periods below the 0.22-day cutoff. Gaia parallaxes were combined with Gaia and 2MASS photometry to obtain G and J-band absolute magnitudes of 674 red variable stars catalogued as contact binaries in the VSX database. The absolute magnitude of main seq…