A stellar phenomenon dubbed the “Tasmanian devil” has left the astronomical community in awe, after emitting flashes of maximum luminosity on more than a dozen occasions, several months after its first appearance.
This peculiar phenomenon, which opens new questions, could shed light on the causes of these explosions, known as fast blue optical transient (FBOTs, for its acronym in English).
From “The Cow” to “Koala”
FBOTs, observable throughout the universe, represent a mystery still unsolved. The first of them, nicknamed “the Cow” after its designation AT2018cow, was detected in 2018 in a galaxy located about 60 million parsecs (equivalent to 200 million light years) from Earth.
“La Vaca” was distinguished by reach a luminosity up to 100 times greater than that of a supernovaand then faded in just a few days, a process that in an ordinary supernova would last for weeks.
Since then, more than half a dozen FBOTs have been identified, with names as varied as “the Koala,” “the Camel,” and, most recently, “the Finch.”
However, the underlying cause of these phenomena remains an enigma. Prevailing hypotheses suggest that they could be failed supernovae (stars that collapse into a black hole or neutron star before they can explode), intermediate mass black holes devouring other stars, or the result of the interaction between objects and the extremely hot and bright stars known as Wolf-Rayet stars.
The demon of Tasmania
In a study published November 15 in the journal Naturea team led by astronomer Anna Ho of Cornell University in Ithaca, New York, describes recent activity at an FBOT discovered approximately 1 trillion parsecs away in September 2022.
Ho was responsible for developing the software that, in September 2022, detected the event signal while processing around half a million variations or transient events recorded daily. This analysis was carried out as part of an exhaustive mapping of the sky carried out by the telescope Zwicky Transient Facilitylocated in California, United States.
In December 2022, while routinely monitoring the explosion, which was in the process of fading, the team noticed something unusual in one of the images analyzed: a flash of light followed by a sudden spike in luminosity in the center of the image, which disappeared as quickly as it appeared.
They recorded a total of 14 such events, each lasting just a few minutes.
Ho suggests these flashes could support the foiled supernova theory.which would imply a massive star, approximately 20 times larger than the Sun, exhausting its fuel and collapsing, leaving behind a dense neutron star or black hole inside the stellar remains.
Additional observations could help determine the mass of the object, which could definitively explain its origin. According to Ho, if an intermediate mass black hole is a black hole of 10,000 solar masses, a frustrated supernova is more like 10 or 100 solar masses.
The flares could offer a way to estimate the object’s mass: when measuring a rapidly changing signal, how quickly that signal varies can be used to estimate the size of the emitting object. A high speed would indicate that the object is rotating rapidly, which would suggest a lower mass.
The Vera C. Rubin Observatory, currently under construction in Chile and scheduled to launch next year, is expected to find 10 to 100 times more of these objects. This could help astronomers narrow down the causes of these strange phenomena.