Search for Northern Hemisphere Rapidly Oscillating Ap stars

Abstract

Rapidly oscillating Ap (roAp) stars are cool, magnetic, chemically peculiar A-F type stars which exhibit high frequency oscillations similar to that of the famous five minute oscillations of Sun. These oscillations are interpreted as low degree (l<3), high order (n >10-30), non-radial p-mode oscillations. The periods of these pulsations lie in the range of 4-16 minutes with typical amplitudes of few milli-magnitudes (< 8mmag) in the Johnson-B filter. More than a dozen roAp stars are multiperiodic, making them suitable for asteroseismology. The presence of high magnetic fields (of the order of few kG) in these stars gives us a chance to study the effects of magnetic fields on pulsations.

The thesis presents the efforts to search for new roAp stars in the northern hemisphere and its results.