SU Aur: A deep fading event in Visible and near-infrared bands

In three seasons of 2015-2018 we carried out a series of visible and near infrared (NIR) photometry of SU Aur. In course of this photometric monitoring we detected an event of a deep fading of the star in spring of 2018. In this paper we present preliminary analysis of our photometry.Comment: 4 pages, 2 figure

The eclipsing binary star RZ Cas: Accretion-driven variability of the multimode oscillation spectrum

We analysed photometric time series of the active, semidetached Algol-type system RZ Cas obtained in 1999-2009, in order to search for seasonal and short-term variations in the oscillation spectrum of RZ Cas A. The orbital period shows ±1 s cyclic variations on time-scales of 6-9 years. We detected six low-degree p-mode oscillations with periods between 22.3 and 26.22 min and obtained safe mode identifications using the periodic spatial filter method. The amplitudes and frequencies of all modes vary. We tested and confirm the hypothesis that rapid variations in the pulsation spectrum of the mass-accreting component and rapid increases in the orbital period are driven by high mass transfer and accretion outbursts caused by the cyclic magnetic activity of the Roche lobe-filling donor star. Two rapid pulsation-amplitude decays observed in 2001 and 2009 can be explained by high-mass transfer events separated by the duration of the last 9-yr long magnetic cycle.We also tested and confirm the hypothesis of an acceleration of the outer envelope of the pulsating component. We discovered synchronous, modal m-dependent variations in the frequencies of three identified modes, in good agreement with results of our mode identification using the periodic spatial filter method. We suggest that m-dependent pulsation frequency variations are caused via the Doppler-effect by variations of the rotation speed of the outer envelope of the pulsating gainer. With this method, we obtained the first asteroseismic detection and accurate measurement of the accretion driven acceleration of the outer envelope of the massaccreting component of an Algol-type star.© 2017 The Author(s).DEM acknowledges his work as part of the research activity supported by the National Astronomical Research Institute of Thailand (NARIT), Ministry of Science and Technology of Thailand. HL acknowledges support by the DFGgrant LE 1102/3-1. ER and MGLJ acknowledge support MINECO/Spain projects AYA2014-54348-C3-1-R, ESP2014-54362-P and ESP2015-65712-C5-5-R. VT acknowledges support from RFBR grant no. 15-52-12371. SJ acknowledge the grant received from Indo-South Africa Science and Technology Cooperation INT/SAFR/P-3(3)2009) and NRF grant UID69828 funded by Departments of Science and Technology of the Indian and South African Governments under which the photometric observations were carried out from ARIES. KA, RK acknowledge their work as a research activity in the framework of Project No. 0075/GF4 'Investigation of the Variability of Stars and the Processes of Substance Exchange With a Gas-Dust Disk' DEM thanks E. Soydugan for providing her 2002 observations of RZ Cas for re-analysis. MDE thanks amateur astronomer Kari Tikkanen (Oulu University) for providing us, when we were searching for evidences of orbital period jump, his visual observations, which safely showed the orbital period jump in RZ Cas in the years 2000-2001

The eclipsing binary star RZ Cas: Accretion-driven variability of the multimode oscillation spectrum

We analysed photometric time series of the active, semidetached Algol-type system RZ Cas obtained in 1999-2009, in order to search for seasonal and short-term variations in the oscillation spectrum of RZ Cas A. The orbital period shows ±1 s cyclic variations on time-scales of 6-9 years. We detected six low-degree p-mode oscillations with periods between 22.3 and 26.22 min and obtained safe mode identifications using the periodic spatial filter method. The amplitudes and frequencies of all modes vary. We tested and confirm the hypothesis that rapid variations in the pulsation spectrum of the mass-accreting component and rapid increases in the orbital period are driven by high mass transfer and accretion outbursts caused by the cyclic magnetic activity of the Roche lobe-filling donor star. Two rapid pulsation-amplitude decays observed in 2001 and 2009 can be explained by high-mass transfer events separated by the duration of the last 9-yr long magnetic cycle.We also tested and confirm the hypothesis of an acceleration of the outer envelope of the pulsating component. We discovered synchronous, modal m-dependent variations in the frequencies of three identified modes, in good agreement with results of our mode identification using the periodic spatial filter method. We suggest that m-dependent pulsation frequency variations are caused via the Doppler-effect by variations of the rotation speed of the outer envelope of the pulsating gainer. With this method, we obtained the first asteroseismic detection and accurate measurement of the accretion driven acceleration of the outer envelope of the massaccreting component of an Algol-type star. © 2017 The Author(s)