flashes to more modern source
A Yale astronomer and collaborators using X-ray, radio and optical telescopes have announced a major clarification in the origin of mysterious objects known as X-ray flashes.
The researchers found that X-ray flashes originate from blue star-forming galaxies whose distances are estimated to be between 6 and 11 billion light years from Earth. This effectively ends the widely-held speculation that X-ray flashes were formed when the universe was in its infancy.
X-ray flashes resemble a lower energy and longer-duration version of a gamma-ray burst -- an energetic explosion thought to signal the death of a massive star. The properties of X-ray flashes led to speculation that they were gamma-ray bursts occurring less than a few billion years after the Big Bang, and whose light had been subsequently weakened and time-stretched by the expansion of the universe.
According to researchers, now that the very distant origin of X-ray flashes has been ruled out, the X-ray flashes could be due to exploding massive stars, like gamma-ray bursts.
A galaxy's blueness is often taken as a crude measure of the rate of star formation, as well as having implications for distance. "Those two galaxies in which the flashes occurred are incredibly blue," says Pieter van Dokkum, assistant professor of astronomy and a co-author of the study to be published later this year in The Astrophysical Journal. "These X-ray flash hosts are churning out stars at an appreciable rate for their size."
The location of the sources studied by the researchers required a careful coordination of NASA's Chandra X-ray Observatory and Hubble Space Telescope, along with the National Radio Astronomy Observatory's Very Large Array (VLA) in Socorro, New Mexico. Chandra and the VLA provided a precise location of the fading X-ray and radio "afterglow" of two X-ray flashes known as XRF 011030 and XRF 020427. The Hubble Space Telescope was used to identify and study galaxies at these locations and estimate their distances to between six and 11 billion light years from Earth.
The lead author is Joshua Bloom of the Harvard Smithsonian Center for Astrophysics in Cambridge. Co-authors, in addition to van Dokkum, include Derek Fox, Shri Kulkarni, Edo Berger, and George Djorgoyski, all of the California Institute of Technology, and Dale Frail of the National Radio Astronomy Observatory's VLA in Socorro, New Mexico.
--By Jacqueline Weaver
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