Janet Akyuz Mattei

Orbital Light Curve of the Peculiar Binary V Sagittae in ExtendedHigh States of Brightness

We have analyzed the orbital modulation of V Sge in two intervals, each several years long, when the long-term light curve was relatively flat, in extended high state of brightness, and displayed just minor fluctuations. We used extensive sets of the visual AAVSO data. The two-sided moving averages with various values of Q were applied to the data folded with the orbital photometric phase – it allowed to pick out the general properties of the orbital component of the variations. We found that the modulation is always present but its shape near the secondary minimum (phase 0.5) remarkably varies for the two respective intervals. The secondary minimum is very prominent in one interval, but is almost absent in other interval. The standard deviation of brightness, computed for each bin of the folded light curve, displays variations through the orbital phase and has its minimum near phase 0.6. All these findings are confirmed for various values of Q. We argue that the source of the scatter of the orbital modulation is located in the lobe of the primary between its center and the L1 point, shifted slightly from the line of centers of the stars.

Activity of the super‐soft X‐ray source V Sge

An analysis of the activity of the super‐soft X‐ray source (SSXS) V Sge is presented. The long‐term (decades) increase of the mean brightness, revealed by [15], stopped and a decay became apparent. A large change of the character of the high/low state behaviour occurred in the last several years. The light curve displays a more complicated profile than in the previous segment of high/low state activity (1991–1995). Nowadays, episodes of long low states occur in a cycle of about 400 days, with superposed brief and less deep fadings. Similarities between the behaviour of V Sge and another SSXS RX J0513.9‐6951 are pointed out. We argue that real mass transfer variations occur in V Sge, in variance with the model for the contracting and expanding H‐burning white dwarf in J0513, proposed by [11].

Hands-On Astrophysics: Variable Stars for Astronomy Education and Development

Amateur astronomers, and students, can contribute to astronomical research by measuring the brightness of variable stars. Hands-On Astrophysics (HOA) is a project which uses the unique methods and the International Database of the American Association of Variable Star Observers (AAVSO) to develop and integrate a wide range of science, mathematical and computer skills, through the measurement and analysis of variable stars. It is very flexible and can be used at many levels, in many contexts — for classroom use from high school to university level, or for individual projects. In this paper we describe HOA, and how it can be used to promote international astronomy education and development, through research-based science education.