INTEGRAL detection of accreting white dwarf
Credit:Service d'Astrophysique(SAp), CEA France; artist view: Mark Garlick

Hidden Dwarfs Exposed

The high energy Universe is still only poorly explored. Sources of energetic emission (at energies of a more than 10 thousand electron volts or higher) include active galactic nuclei, neutron star and black hole systems. But what else? Recent observations by the INTEGRAL Gamma-ray astrophysical laboratory of the Universe found more than 400 individual sources of hard X-ray emission, but only managed to identify about 300 of them. A recent study shows that at least some of these sources are unusual systems consisting of a "normal" star which is being stripped of material by a white dwarf companion. One example is the source IGR J00234+6141, one of the faintest sources positively detected by INTEGRAL. The position of this source in Galactic coordinates is shown above; it lies within the plane of the Milky Way. The image on the lower left shows a close-up view of this source from the ISGRI camera on INTEGRAL. On the right is shown an optical image of the ISGRI source circle, showing dozens of possible counterpart sources. But the counterpart to IGR J00234+6141 was identified and is shown by the arrow. The counterpart is a low mass binary system containing a highly magnetized white dwarf, a burnt-out cinder of a low-mass star. These systems belong to a sub-class of accreting white dwarf binary stars called "Intermediate Polars". In intermediate polars, the magnetic field of the white dwarf is so strong that it channels the accreting material into a "sheet" flowing onto the magnetic poles of the white dwarf, as shown in the dramatic artist rendition in the upper right.

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Page Author: Dr. Michael F. Corcoran
Last modified Thursday, 03-May-2012 14:23:06 EDT

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