Search for and Study of Photometric Variability of Magnetic White Dwarfs WD 2047+372 and WD 0009+501

Abstract

We report the results of long-term photometric observations of the magnetic white dwarfs WD 2047+372 and WD 0009+501, aimed to search for and study regular brightness variability in these stars. The data in the V band of the Johnson filter revealed signs of irregular variability in the convectively inactive white dwarf WD 2047+372 at times from hours to 1–3 days with characteristic amplitudes of about 0^m. 005. This variability can be due to both irregular proper pulsations of the star or even the debris disk and reasons of unidentified instrumental nature. We have not found the brightness variability of WD 2047+372 at the level of greater than 0^m. 005. As distinct from WD 2047+372, the convectively active magnetic white dwarf WD 0009+501 shows stable photometric variability associated with the proper rotation of the object and correlating with the variability of its magnetic properties. The variability amplitude is about 0^m. 01. Based on comparison of the observations of these two targets, we concluded on the photometric variability of magnetic dwarfs located in the thermal convection zone. We noticed the stable variability on long-term timescales (years, decades, and over).