Stars Need to be Part of Binary Systems to Create the Brightest Explosions in the Universe

In order for a massive and incredibly bright explosion to take place in the Universe, two stars are needed. Astronomers from the University of Warwick have discovered the fact that this process requires two stars to generate a gamma-ray burst.

A new study addresses the enigma of how stars spin sufficiently fast to create conditions to expel a jet of highly energetic material into cosmos and had discovered that tidal impacts such as those between the Moon and Earth are the answer.

Some Basic Requirements

The finding, published in the Monthly Notices of the Royal Astronomical Society journal, had been conducted with simulated models of thousands of binary star arrays. Over half of all stars are located in a binary star system, and this new paper has demonstrated that they need to be in paired star systems for them to create a massive explosion.

​A long gamma-ray burst (GRB), the kind analyzed in this research, happens when a gigantic star approximately then times the size of the Sun goes supernova, shatters into a neutron star or black hole, and expels a proportionate jet of materials into the cosmos.

Rather than of the object collapsing inwards, it smashes into a disc to preserve angular momentum. While the material falls inwards, that angular momentum releases it as a jet along the polar axis. However, for that jet of material, the cosmic object needs to be rotating sufficiently fast to launch material along the axis.

The researchers used simulation models to understand this concept and found that the impacts of tides from a close adjoin could be the reason why these stars spin at the pace required to generate gamma-ray bursts. Gamma-ray bursts are the brightest occurrences in the Universe and are visible from Earth when their jet of material is headed straight at us.

Binary System Population Synthesis

Lead author Ashley Chrimes, a Ph.D. student at the University of Warwick Department of Physics, said: “We’re predicting what kind of stars or systems produce gamma-ray bursts, which are the biggest explosions in the Universe. Until now, it’s been unclear what kind of stars or binary systems you need to produce that result.

“The question has been how a star starts spinning or maintains its spin over time. We found that the effect of a star’s tides on its partner is stopping them from slowing down, and, in some cases, it is spinning them up. They are stealing rotational energy from their companion, a consequence of which is that they then drift further away.

“What we have determined is that the majority of stars are spinning fast precisely because they’re in a binary system.”

The research uses multiple binary stellar development models designed by the scientists from the University of Warwick and Dr. J.J. Eldridge from the University of Auckland. Employing a method called binary population synthesis, the team was able to simulate this process in a population of thousands of star systems and so detect the rare instances where a blow-off of this kind can take place.

Dr. Elizabeth Stanway, from the University of Warwick Department of Physics, said: “Scientists haven’t modeled in detail for binary evolution in the past because it’s a very complex calculation to do. This work has considered a physical mechanism within those models that we haven’t examined before, which suggests that binaries can produce enough GRBs using this method to explain the number that we are observing.”