Nova-Like Cataclysmic Variable TT Ari: QPO Behaviour Coming Back From Positive Superhumps

TL;DR

This study analyzes the variability and QPO behavior of TT Ari, a nova-like cataclysmic variable, during its transition from positive to negative superhump states, revealing consistent QPO periods and significant short-term variations.

Contribution

It provides detailed observational analysis of TT Ari's QPOs and superhump states, highlighting the stability of QPO periods and variability across different activity phases.

Findings

QPOs have a mean period of 21.6 minutes with semi-amplitude of 36 mmag.

The QPO period does not show secular decrease over time.

Significant night-to-night variations in QPO period and amplitude.

Abstract

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 $T_{min}=BJD 2453747.0700(47)+0.132322(53)E.$ 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.