Orbital periods of cataclysmic variables identified by the SDSS. IV. SDSS J220553.98+115553.7 has stopped pulsating

Abstract

We present time-series VLT spectroscopy and NTT photometry of the cataclysmic variable SDSS J220553.98+115553.7, which contains a pulsating white dwarf. We determine a spectroscopic orbital period of 82.825 +/- 0.089 min from velocity measurements of the Halpha emission line. A period analysis of the light curves reveals a dominant periodicity at 44.779 +/- 0.038 min which is not related to the spectroscopic period. However, the light curves do not exhibit a variation at any frequency which is attributable to GW Lib type pulsations, to a detection limit of 5 mmag. This non-detection is in contrast to previous studies which have found three pulsation frequencies with amplitudes of 9 to 11 mmag at optical wavelengths. Destructive interference and changes to the thermal properties of the driving layer in direct response to accretion can be ruled out as causes of the non-detection. Alternatively, it is feasible that the object has cooled out of the instability strip since a previous (unobserved) dwarf nova superoutburst. This would be the first time this behaviour has been seen in a cataclysmic variable pulsator. Another possibility is that changes in the surface characteristics, possibly induced by accretion phenomena, have modified the surface visibility of the pulsation modes. Further observations, particularly improved constraints on the timescale for changes in the mode spectrum, are needed to distinguish among possible explanations.

Accepted for publication in MNRAS; 7 pages and 6 figures. The data will be available from http://www.astro.keele.ac.uk/~jkt

References in corpus (6)

• The Donor Stars of Cataclysmic Variables
• Pulsational Instabilities in Accreting White Dwarfs
• VLT/FORS spectroscopy of faint cataclysmic variables discovered by the Sloan Digital Sky Survey
• HST/STIS Spectroscopy and Modeling of the Long Term Cooling of WZ Sagittae following the July 2001 Outburst
• SDSS J233325.92+152222.1 and the evolution of intermediate polars
• HST and Optical Observations of Three Pulsating Accreting White Dwarfs in Cataclysmic Variables

Cited by in corpus (5)

• Evidence for reduced magnetic braking in polars from binary population models
• Orbital periods of cataclysmic variables identified by the SDSS. V. VLT, NTT and Magellan observations of nine equatorial systems
• Orbital periods of cataclysmic variables identified by the SDSS. IX. NTT photometry of eight eclipsing and three magnetic systems
• R-mode oscillations in accreting white dwarfs in cataclysmic variables
• The fainter the better: cataclysmic variable stars from the SDSS