The Vink: A Rare Blue Flash Discovery Outside the Galaxy

We already had a cow, a koala, a camel and a Tasmanian devil. Now we also have a finch – from outside our galaxy even. A team of astronomers led by Dutch researchers has discovered a blue flash that is not located within a star-forming region as usual, but even outside a galaxy. They baptized the phenomenon ‘the Vink’ (the Finch) in line with previous blue flashes such as the Cow, the Koala, the Camel and the Tasmanian Devil. They will soon publish their findings MNRAS Letters. There is already one preprint.

Of website van SRON (Netherlands Institute for Space Research) with the discovery.

In 2018, astronomers witnessed an intense explosion that was ten to a hundred times brighter than the average supernova. This explosion was designated AT2018cow, nicknamed ‘the cow’. It was the first example of bright fast blue optical phenomena (Luminous Fast Blue Optical Transients aka, LFBOTs). So far, only a handful of these remarkable events have been recorded. They were each nicknamed the name of an animal, inspired by the last letters of their astronomical designation.

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The bright fast blue flashes are only visible for a few days. This is in contrast to supernovas, which last weeks or months. It’s unclear what causes these flashes, and the latest blue flash only raises more questions. Because unlike the previous blue flashes, the Chaffinch is not in a galaxy, but outside it. De Vink is located between a spiral galaxy and a satellite galaxy.

Rare type of supernova

Until now, the blue flashes were thought to be a rare type of supernova. But supernovae are formed from large stars that live only a short time and do not have time to break away from the galaxy in which they formed.

Because the flashes appear quickly and disappear quickly, astronomers look for them with telescopes that continuously monitor large swathes of sky. The Chaffinch was discovered with the Zwicky Transient Facility, which maps the entire northern sky every two days. Once the Chaffinch was discovered, the researchers initiated a series of pre-planned observations. They looked with the Gemini South telescope, the Hubble space telescope, the Chandra space telescope and the Very Large Array.

To explain the Chaffinch’s unusual location, researchers think it may have been the result of the explosion of an extremely fast-moving star. An alternative hypothesis is that it concerns two neutron stars that have been moving towards each other in increasingly tighter spirals for billions of years and collided with each other.

Elucidate

In the future, astronomers hope to discover more blue flashes so they can elucidate the phenomenon. They have pinned their hopes, among other things, on the Vera C. Rubin Observatory under construction in Chile. That telescope will scan the entire southern sky every few nights.

AT2023fhn (the Finch): a Luminous Fast Blue Optical Transient at a large offset from its host galaxy. Door: AA Chrimes, PG Jonker, et al. Accepted for publication in MNRAS Letters. [preprint]