Abstract

Angular Momentum Evolution of the cataclysmic variable V455 Andromedae

Anjum Mukadam (University of Washington)

Stylianos Pyrzas (Universidad Catolica del Norte), D. M. Townsley (University of Alabama), B. T. Gaensicke & J. J. Hermes (University of Warwick), and Paula Szkody (University of Washington).

We have acquired time-series photometry on the cataclysmic variable V455 Andromedae (hereafter V455 And, HS2331+3905) since its discovery. The lightcurves reveal a rotation period shorter than the orbital period of 81.1 min, implying the presence of a magnetic field. We expect that the magnetic field of this interacting white dwarf channels the accreted matter from the disk towards the white dwarf poles, classifying it as an Intermediate Polar. The two polar spinning hot spots are visible in the lightcurves at the rotation period of 67.61970396 +/- 0.00000074s, and its harmonic. Using photometric observations of V455 And obtained from October 2007 to 2013, we constrain the rate of change of its spin period with time to be dP/dt = (-7.8 +/- 7.0)e-15 s/s employing the O-C method, and (-6.0 +/- 6.2)e-15 s/s with a direct non-linear least squares fit. The large uncertainties imply that there is no significant detection of a changing spin period for the duration October 2007--2013. V455 And underwent a large amplitude dwarf nova outburst, beginning on the 4th of September 2007. The data obtained prior to the outburst have relatively larger uncertainties, but reflect a period 4.8 +/- 2.2 microseconds longer than the best-fit post-outburst spin period. The angular momentum gained by the white dwarf from matter accreted during outburst as well as the white dwarf's slight subsequent shrinking should both cause the star to spin slightly faster after the outburst. Assuming that the mass of V455 And is 0.6 solar mass, we estimate that the change in spin period due to the outburst should be 5 microseconds, consistent with the empirical value of 4.8 +/- 2.2 microseconds.

Mode of presentation: oral