DCU researchers find solution to question which has puzzled astronomers for a decade
A research team led by DCU academic Dr. Masha Chernyakov has devised a new model to explain the rationale for the existence of strong light flares in a star system, which has puzzled scientists for more than a decade.
Observing the night sky with telescopes, scientists found out that many of the stars are grouped together, forming so-called binary systems where one star is orbiting around another one.
The interaction between these two stars can lead to many interesting effects.
In particular some of these systems become visible not only in visible light, but also in radio and X-rays.
One object in such systems is known to be a very massive bright star while the second object is much smaller and can be either a neutron star (an object which is about the same mass as the Sun, but measures 20 km in size) or a black hole.
Tiny bits of these systems also emit much more energetic light at what is known as GeV and TeV energies which are billion and trillion times more energetic than visible light and exceed the energy of the most powerful human-built accelerator, the Large Hadron Collider (LHC).
One such system, the PSR B1259-63, located in the Crux constellation, puzzled scientists for a long time producing giant flares only in GeV energy range.
The second object in this system is known to be a rapidly rotating neutron star.
The rotation of the neutron star in this system slows with time, and scientists believe that it is the accompanied energy release that makes the system so bright at high energies.
Therefore, it came out as a total surprise when the Fermi telescope detected incredibly strong GeV flares which released up to 30 times more energy than it was thought to be available in the system (equivalent to 10 quadrillion mega tonne).
Recently, a research team led out of DCU, was, for the first time able to propose a model explaining both the observed energy release and also why these flares are visible only at GeV and are not seen at any other energies.
The group found that the GeV radiation is formed during the interaction of usual and monoenergetic neutron star outflows.
They also found that due to the shape of the interaction surface, the GeV radiation is not emitted in all directions, but rather as a torchlight's beam looks at the Earth's direction at the time of the GeV flare.
This model provides an explanation for the apparent discrepancy in the energy budget in this system and details of the flare.
Dr. Masha Chernyakova said,
"This system has intrigued me for a long time, revealing more and more surprises with each set of observations.
I have studied it for more than 20 years already and our new model seems to be able to answer a number of questions that were actively discussed in the community for a long time.
In particular we understood for the first time the origin of the enigmatic gamma-ray flares and were able to measure the energy of the relativistic electrons in the neutron star outflow.”
The paper was accepted to MNRAS (Monthly Notices of the Royal Astronomical Society) on June 26.
Research team Dr. Masha Chernyakova, DCU and co-authors include Dr. Denys Malyshev (University of Tuebingen, Germany), Samuel McKeague (PhD student, DCU), Dr. Brian van Soelen and PhD student Johannes P. Marais (University of the Free State, South Africa), Dr. Antonio Martin-Carrillo and Dr. David Murphy (UCD).