Two astronomers have proposed a new path for the formation of a newly discovered class of millisecond pulsars with similar orbital periods and eccentricities.
In the scenario of Paulo Freire and Thomas Tauris, a massive white dwarf star accretes matter and angular momentum from a normal companion star and grows beyond the critical Chandrasekhar mass limit.
However, it does not collapse immediately into a neutron star because it is rotating very fast and is thus sustained by centrifugal forces.
After the mass transfer ceases, this massive white dwarf loses rotational energy and eventually collapses directly into a millisecond pulsar, without the need for further accretion.
The associated instantaneous release of gravitational binding energy is expected to produce the characteristic eccentricities observed in such systems. The new hypothesis makes several testable predictions about this recently discovered subclass of millisecond pulsars.
If confirmed, it opens up new avenues of research into the physics of stars, in particular the momentum kicks and mass loss associated with accretion induced collapse of massive white dwarfs.
The new hypothesis includes the collapse of a massive white dwarf after accretion has terminated. It explains not only the similarity of eccentricities and companion masses, but also their values.
Thomas Tauris , affiliated with both, Argelander-Institut fur Astronomie and Max-Planck-Institut fur Radioastronomie (MPIfR) in Bonn, said that he was surprised when they looked at the calculated orbital periods and eccentricities predicted by our model, asserting that it gives an exact match with the observations.
The paper has been published in Monthly Notices of the Royal Astronomical Society. (ANI)