Rotational period of WD 1953 — 011 — a magnetic white dwarf with a star-spot

• Published in: Monthly notices of the Royal Astronomical Society Vol. 357; no. 1; pp. 333 - 337
• Main Authors: Brinkworth, C. S., Marsh, T. R., Morales-Rueda, L., Maxted, P. F. L., Burleigh, M. R., Good, S. A.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 11.02.2005; Blackwell Science
• Subjects: stars: individual: WD 1953-011; stars: magnetic fields; stars: rotation; stars: spots; white dwarfs; Balmer lines; White dwarf stars; stars: magnetic fields; Equivalent width; stars: individual: WD 1953-011; white dwarfs; Starspots; stars: spots; Dwarf stars; Spectroscopical observation; Sunspots; stars: rotation; Photometry
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1111/j.1365-2966.2005.08649.x

WD 1953-011 is an isolated, cool (7920 ± 200 K) magnetic white dwarf (MWD) with a low average field strength (∼70 kG), and a higher than average mass (∼0.74 M⊙). Spectroscopic observations taken by Maxted et al. showed variations of equivalent width in the Balmer lines, unusual in a low-field white dwarf. Here we present V-band photometry of WD 1953-011 taken at seven epochs over a total of 22 months. All of the data sets show a sinusoidal variation of approximately 2 per cent peak-to-peak amplitude. We propose that these variations are due to a star-spot on the MWD, analogous to a sunspot, which is affecting the temperature at the surface, and therefore its photometric magnitude. The variations have a best-fitting period over the entire 22 months of 1.4418 d, which we interpret as the rotational period of the white dwarf.