43 research outputs found
Nova-Like Cataclysmic Variable TT Ari: QPO Behaviour Coming Back From Positive Superhumps
We study the variability of the nova-like cataclysmic variable TT Ari, on
time-scales of between minutes and months. The observations in the filter R
were obtained at the 40-cm telescope of the Chungbuk National University
(Korea). TT Ari was in the "negative superhump" state after its return from the
"positive superhump" state, which lasted 8 years. The ephemeris for 12 best
pronounced minima is where
numbers in digits are errors in units of the last digit. The phases of minima
may reach 0.2, indicating non-eclipse nature of these minima. The
quasi-periodic oscillations (QPO) are present with a mean "period" of 21.6 min
and mean semi-amplitude of 36 mmag. This value is consistent with the range
15-25 minutes reported for previous "negative superhump" states and does not
support the hypothesis of secular decrease of the QPO period.
Either the period, or the semi-amplitude show significant night-to-night
variations. According to the position at the two-parameter diagrams, the
interval of observations was splitted into 5 parts, showing different
characteristics which are discussed in this paper. The system is an excellent
laboratory to study processes resulting in variations at time-scales from
seconds to decades and needs further monitoring at various states of activity.Comment: 14pages,10figures, accepted in Astronomy and Astrophysic