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The Mass Accretion Rate of the Young Variable Star GM Cep

GM Cep is a young Pre-Main Sequence source that presents rapid photometric variability of more than 2 mag in the optical bands. First studies have interpreted such variations as possible EXor-type outbursts, but subsequently important arguments in favor of a quasi-periodical UXor- type variability have been provided. A powerful way to determine whether or not GM Cep is an eruptive variable is to evaluate the variation of the mass accretion rate between low- and high-brightness phases. Between 2017 November and 2018 April GM Cep underwent a brightness increase from V ~ 14.8 to ~13.3 mag, then followed by a new fading at the end of April. We have observed GM Cep with the 1.22 m telescope + B&C spectrograph operated in Asiago by the University of Padova, obtaining seven spectra in the wavelength range between 3300 and 8050 Å. We have collected optical BVRI photometry and determined the extinction toward the source by means of color–color diagrams. We can affirm that the mass accretion rate has remained substantially unchanged during our monitoring period. The source brightness has changed from 14.8 to 13.3 mag.

stars: formation ; stars: individual (GM Cep) ; stars: pre-main sequence ; stars: variables: T Tauri, Herbig Ae/Be

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