Last year, astronomers spotted a one-of-a-kind pulsating white dwarf. Now, they have announced that the object is the first confirmed white dwarf pulsar.
As reported in Nature Astronomy, researchers from the University of Warwick and the South African Astronomical Observatory have confirmed that AR Scorpii (AR Sco) is indeed a white dwarf pulsar. The star is in a binary system with a red dwarf star and is located 380 light-years from Earth.
White dwarf pulsars have been theorized for many years. White dwarfs are the end product of stars that are not too big, while pulsars are highly-magnetized, quickly-spinning neutron stars (the end product of some of the bigger stars). So, theoretically, one could have a highly-magnetized, quickly-spinning white dwarf.
But such an object has eluded astronomers for decades, until last summer when AR Scorpii was seen "whipping" its red companion with a stream of particles. The white dwarf spins on itself every 2 minutes and has a magnetic field 100 million times larger than Earth’s own. This is what one would expect from a pulsar.
“AR Sco is like a gigantic dynamo: a magnet, size of the Earth, with a field that is ~10.000 stronger than any field we can produce in a laboratory, and it is rotating every two minutes,” Professor Boris Gänsicke, from the University of Warwick, said in a statement. “This generates an enormous electric current in the companion star, which then produces the variations in the light we detect.”
The stream of particles from the white to the red dwarf accelerates electrons from the red star atmosphere to almost the speed of light. This phenomenon has never been witnessed before.
The white dwarf has been seen to increase its brightness by a factor of four, and although it’s about the size of our planet, it is around 200,000 times more massive.
“The new data show that AR Sco's light is highly polarised, showing that the magnetic field controls the emission of the entire system, and a dead ringer for similar behaviour seen from the more traditional neutron star pulsars,” Professor Tom Marsh, also from the University of Warwick, added.
The two stars in the system rotate around each other every 3.56 hours and are 1.4 million kilometers (870,000 miles) apart, over three and a half times the distance between the Earth and the Moon.