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5h ago

Astronomers Find Long-Lived Bow Shock Around Diskless White Dwarf, Defying Models

VLT/MUSE mapping ties the nebula to RXJ0528+2838, exposing an outflow whose longevity exceeds what the measured magnetic field can power.

The central square image, taken with the MUSE instrument on ESO's Very Large Telescope, shows shock waves around the dead star RXJ0528+2838. When a star moves through space it can push away nearby material creating a so-called bow shock, which in this image is glowing in red, green and blue. The colours represent hydrogen, nitrogen and oxygen, respectively. These shocks are usually produced by a strong outflow expelled from the star. However, in the case of RXJ0528+2838 –– a white dwarf with a Sun-like companion –– astronomers discovered that the shock wave can’t be explained by any known mechanism. Some hidden energy source, perhaps magnetic fields, could be the answer to this mystery. European Southern Observatory (ESO)/K. Ilkiewicz and S. Scaringi et al./Handout via REUTERS
Image
The central square image, taken with the MUSE instrument on ESO's Very Large Telescope, shows shock waves around the dead star RXJ0528+2838. When a star moves through space it can push away nearby material creating a so-called bow shock, which in this image is glowing in red, green and blue. The colours represent hydrogen, nitrogen and oxygen, respectively. These shocks are usually produced by a strong outflow expelled from the star. However, in the case of RXJ0528+2838 –– a white dwarf with a Sun-like companion –– astronomers discovered that the shock wave can’t be explained by any known mechanism. Some hidden energy source, perhaps magnetic fields, could be the answer to this mystery. European Southern Observatory (ESO)/K. Ilkiewicz and S. Scaringi et al./Handout via REUTERS

Overview

  • Published in Nature Astronomy on January 12, the study reports a first-of-its-kind persistent bow shock around the polar white dwarf RXJ0528+2838 despite the absence of an accretion disc.
  • ESO’s VLT/MUSE spectroscopic imaging identified hydrogen, nitrogen and oxygen emission, confirmed the structure originates from the binary, and ruled out an unrelated nebula or an old nova remnant.
  • The bow shock’s size and shape indicate a sustained outflow for roughly 1,000 years, pointing to long-term mass and energy loss from the system.
  • The source lies about 730 light-years away in Auriga and comprises a highly magnetized white dwarf with a low-mass red dwarf companion in an ~80-minute orbit at very close separation.
  • Measured magnetic power could maintain such an outflow for only a few hundred years, leaving the driving mechanism unresolved and motivating searches for similar systems and future ELT follow-up.