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2009 Superoutburst of Dwarf Nova 1RXS J053234.9+624755

Rutkowski A., Olech A., Poleski R., Sobolewska M., Kankiewicz P., Ak T., Boyd D.

Acta Astronomica

2010

Vol. 60, No. 4

337--355

We present photometric observations of the dwarf nova 1RXS J053234.9+624755. We performed a detailed analysis of the superoutburst that occurred in August 2009. We found the superhump period to be Psh=0.057122(14) days. Based on the O-C diagram we conclude that Psh increased during the plateau at the rate of dPsh/dt=(9.24±1.4)×10-5. Both the O-C analysis and evolution of the superhumps light curve favor the model in which superhumps originate in a variable source located in the vicinity of the hot spot. In addition, the evolution of the light curve suggests that the superhump light source approaches the disk plane as the superoutburst declines. Detailed analysis of the superoutburst plateau phase enabled us to detect a signal which we interpret as apsidal motion of the accretion disk. We detected additional modulations during the final stage of the superoutburst characterized by periods of 104 s and 188 s which we tentatively interpret as quasi periodic oscillations. Estimations of A0 and An are in agreement with the dependence between the amplitude of superhumps and the orbital inclination.

Stability of the Most Hazardous Mars-Crossers

Kankiewicz P., Włodarczyk I.

Acta Astronomica

2006

Vol. 56, No. 4

413--425

The equations of motion of 4190 Mars Crossers (MCs) were numerically integrated to analyze their all possible close approaches to planets in the next 104 years. A sample of asteroids potentially hazardous to Mars was selected and properties of their chaotic motion on larger time scales were determined. For samples of MCs closely approaching Mars, their mean frequency of close encounters was computed. We also analyzed the presence of mean motion and secular resonances. The population of asteroids hazardous to Mars was found and the influence of frequent close approaches and resonances on the stability of their trajectories was estimated. We also estimated the correlation between the frequency of close approaches to Mars and the Lyapunov Time (LT) of these asteroids. Some results concerning the correlation between mean motion/secular resonances and LT were also presented as well as three selected examples of dynamically interesting MCs.