Early reports of a gamma ray burst in the galaxy M31 appear to have been a false alarm.
The Burst Alert Telescope (BAT) onboard the orbiting Swift Observatory detected a sudden burst of energy coming from M31, also called the Andromeda galaxy. This family of stars lies just 2.5 million light years away from Earth.
Gamma Ray Bursts (GRB's) are the most powerful explosions ever witnessed by the human race. They are caused either by a massive star collapsing, or two neutron stars colliding, forming a black hole. This emits a shower of intense radiation that can sterilize vast areas of any life unfortunate enough to be in the vicinity.
When the discovery of a burst of gamma rays in Andromeda was first reported on social media, many members of the public assumed it was a gamma ray burst. Instead, the incident appears to be a false alarm, triggered by objects surrounding the star believed to be at the center of the event.
"We have re-analysed the prompt XRT data on Swift trigger... The initial count rate given... was based on raw data from the full field of view, without X-ray event detection, and therefore may have been affected by other sources in M31, as well as background hot pixels," the SWIFT team reported.
Researchers assigned to the program never stated the reading represented a GRB, but social media became active with stories of a gamma ray burst in a neighboring galaxy.
The source reported as the center of the burst is a known binary system. Astronomers believe it consists of an ultra-dense neutron star paired with an average star, still fusing hydrogen fuel to produce energy. Such systems are not believed to produce gamma ray bursts.
"I guess that enthusiastic followers of astronomy put two and two together and made five, unfortunately. I've even read people saying that there were loads of gamma rays from this object: there definitely weren't. In fact, the Swift-BAT team said that 'this is a faint BAT transient'," Phil Evans, who works on the project, wrote in his blog.
When the outburst was first detected, astronomers thought they were seeing more energy than the small amount that was recorded. Data was released quickly, in a call to other astronomers to turn their attention to the object.
A software glitch also prevented some of the data from SWIFT from reaching researchers on the ground. Once the complete data was analyzed, the nature of the reading was shown to be a relatively low-energy event.
"We therefore do not believe this source to be in outburst," the team stated in a public email.
