A mysterious X-ray flash



NASA’s Chandra X-ray Observatory detected a mysterious flash of X-rays that scientists have never seen before. The source is located in a sky region known as Chandra Deep Field-South (CDF-S) and when erupted it became 1,000 brighter in a few hours producing a thousand times more energy than all the stars in its host galaxy. The host galaxy is most likely a small, faint galaxy about 10.7 billion light years from Earth. No similar events have been found in Chandra observations of other parts of the sky.

There are three possible scenarios that could explain the observed phenomenon, but none of them fits the data perfectly. Two of them suggest that the X-ray source is a gamma ray burst (GRB). GRBs are explosions triggered by either the collapse of a massive star or by the merger of two neutron stars or a neutron star with a black hole. During a GRB explosion a jet is created that is detectable in gamma rays, if the jet points towards Earth. As the jet expands, it loses energy and radiates at X-ray and other wavelengths. The third scenario is that a medium-sized black hole devoured a white dwarf star.

Other unexplained variable X-ray sources have been discovered in the part, but the particular source is roughly 100,000 times more luminous in X-rays and is located in a much smaller and younger host galaxy. Astronomers say that a completely new type of cataclysmic event has been observed. Scientists will search into the Chandra archive and those of ESA’s XMM-Newton and NASA’s Swift satellite in a attempt to find other similar examples that have gone unnoticed.

Future X-ray observations may reveal the same phenomenon in other parts of the sky. If a GRB explosion caused the X-ray flash then gravitational waves would have also been observed. In this case, these events could also be detectable with the Laser Interferometer Gravitational-Wave Observatory (LIGO).


Source: Chandra

Publication: Bauer et al. 2017