First look at a cosmic vampire!

According to RCO News Agency, Using NASA’s Polarization X-ray Imaging Probe (IXPE), MIT astronomers have obtained the first view of the inner region around a dead white dwarf star that is feeding on its companion star like a vampire.

According to Spacey, This research group was able to make a detailed study of the highly energetic region around a white dwarf in the EX Hydrae system, located about 200 light-years from Earth, which was previously inaccessible.

This system is part of the so-called “intermediate polar” group, which is known for emitting a complex pattern of radiation, including X-rays. The EX Hydrae system consists of a white dwarf and its victim star that orbits the dead star every 98 minutes. This makes EX Hydrae one of the closest intermediate polar binaries ever discovered.

Not only did the researchers discover a high degree of polarization among the X-rays, but they were able to trace this energetic radiation to a 3,200-kilometer-high plume of extremely hot stellar material trailing from the companion star and falling onto the white dwarf.

It is about half the radius of the white dwarf itself, and much larger than scientists had previously estimated for such a structure. The research group also detected X-rays that were reflected from the surface of the white dwarf before dispersing. This has been predicted before but never confirmed.

The intermediate poles got their name because of variations in the strength of the white dwarfs’ magnetic fields. When the magnetic field is strong, dead stars attract material from their companions, which then flows toward the white dwarf’s poles. However, when the white dwarfs’ magnetic fields are weak, the detached material forms rotating structures called accretion discs around the white dwarfs. From there, this stolen stellar material gradually feeds the surface of the stellar debris.

The situation is more complicated for vampiric white dwarfs with magnetic fields of moderate strength. Scientists predict that an accretion disk would still need to form for these systems, but this disk would have to be pulled toward the poles of the white dwarfs. Then, the magnetic fields in these systems should pull this material up, creating an outburst of stellar material, or “accretion curtain,” that rains down on the magnetic poles of white dwarfs at millions of miles per hour.

Scientists predict that this downward-sloping material will likely collide with falling material already pulled upward by magnetic fields, creating plumes of turbulent gas that can reach extremely high temperatures and emit X-rays in the process.

The research group planned to test this idea in January 2025 by studying the EX Hydrae system with about seven Earth days worth of observations obtained with IXPE.

These findings demonstrate the effectiveness of X-ray polarimetry, which measures the polarization of X-rays, in investigating intense and violent stellar environments.

“We have shown that X-ray polarimetry can be used to make precise measurements of the accretion geometry of a white dwarf,” said Sean Gunderson, head of the research group. This opens the door to the possibility of performing similar investigations on other types of accreting white dwarfs that have never had the predicted X-ray polarization signals.

This research was published in “The Astrophysical Journal”.

end of message