A Multiwavelength Study of the High‐Field Magnetic White Dwarf EUVE J0317−85.5 (=RE J0317−853)

Abstract

We present optical and ultraviolet photometry and spectroscopy and optical circular spectropolarimetry of the ultramassive, rapidly rotating, high-field magnetic white dwarf EUVE J0317À85.5. From the combined data sets, we establish an ephemeris for the photometric, spectroscopic, and polarimetric variations with a spin period of 725.7277 s, the fastest yet measured for an isolated white dwarf. We build a series of far-ultraviolet (FUV) and optical flux spectra as well as optical polarization spectra that describe the atmospheric properties as a function of rotation phase. Twelve components of the Lyman line series are identified in the FUV: seven of them are forbidden lines enforced by the electric field that permeates the strongly magnetized photosphere. Attempts at modeling the FUV and optical data with two classes of models indicate an unusual field structure on the star. Both offset-dipole and multipolar expansion models fail to adequately reproduce the spectroscopic and polarimetric properties simultaneously, and we postulate that the surface of EUVE J0317À85.5 may be punctuated by a high-field magnetic spot. Subject headings: stars: individual (EUVE J0317À85.5) -stars: magnetic fields -ultraviolet: starswhite dwarfs On-line material: color figure

Constraints on the origin of the massive, hot, and rapidly rotating magnetic white dwarf RE J 0317-853 from an HST parallax measurement

“…the highest known temperature of all MWDs with a field strength above 20 MG (Kawka et al 2007;Külebi et al 2009). Barstow et al (1995) performed high-speed photometry demonstrating that the optical brightness of RE J 0317-853 varies almost sinusoidally with a period of 725.4 ± 0.9 s and an amplitude of more than 0. m 1; these results were confirmed by Vennes et al (2003), who inferred a period of 725.727 ± 0.001 s from the variation in the circular polarisation. The only reasonable explanation of these results is rotation, implying that RE J 0317-853 rotates more rapidly than any other known white dwarf that is not a member of a close binary.…”

“…For RE J 0317-853, it was similarly proposed to explain both the high angular momentum and high mass of this star (Ferrario et al 1997). Vennes et al (2003) also suggested that the scenario could produce a strong and non-dipolar magnetic field. They argued qualitatively that the high angular momentum is a result of the total orbital momentum of a coalescing binary and that the strong nondipolar magnetic field can be generated by dynamo processes due to the differential rotation caused in turn by the merging.…”

“…The optical spectrum together with UV observations taken with the IUE satellite and the Hubble Space Telescope (HST) indicated that RE J 0317-853 possesses a very high effective temperatures in the range from 30 000 to 55 000 K; Barstow et al (1995) achieved their best fit for about 49 000 K. A careful analysis of the EUVE spectrum using the interstellar medium Lyman lines to account for the interstellar extreme ultraviolet absorption implied an effective temperature of 33 800 K (Vennes et al 2003). Within these constraints, RE J 0317-853 is one of the hottest known magnetic white dwarf (MWD); in any case, it has Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.…”

SpitzerIRAC Observations of White Dwarfs. II. Massive Planetary and Cold Brown Dwarf Companions to Young and Old Degenerates

“…- (1 Barstow et al 1995;(9) Ferrario et al 1997;(10) Vennes et al 2003;(11) Bergeron et al 1992; (12) Vennes 1999; (13) Vennes et al 1999;(14) Vennes et al 1996. vMa 2, which was extracted from the Spitzer archive (program 33; PI: G. G. Fazio). These targets are relatively old, with total ages between 1 and 7 Gyr, and are listed in Table 3 for completeness, although their IRAC fluxes are previously published in Paper I with the exception of vMa 2.…”

Si:P as a laboratory analogue for hydrogen on high magnetic field white dwarf stars

“…It has been suggested that magnetic flux densities up to 10 5 T (1 gigagauss) exist on the surface of white dwarf and cataclysmic variable stars [5][6][7] . This inference is based on a complex process that involves a combination of modelling the pattern of flux around the surface and up through the atmosphere of the star, and a search for transitions that are stationary with magnetic field [2][3][4] .…”