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Gaia wins the stellar jackpot


Thanks to the data collected by the satellite Gaia and all observations of a group of amateur astronomers has been possible to discover Gaia14aae, a new class of binary system of Cataclysmic Variables. Its uniqueness lies in the fact that, from our point of view, is perfectly cut, showing an eclipse every 50 minutes.
The Gaia satellite has discovered a binary system is extremely rare, in which one star “eats” the other, but neither contains hydrogen, the most common element in the universe. The system could be an important tool to understand how binary stars explode at the end of their lives.

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Credit: Fraser/ Hodgkin/Campbell/BINSIM

An international team of researchers, with the help of some amateur astronomers has discovered a very peculiar binary system: the first of this type in which one star eclipses the other completely. It is classified as a cataclysmic variable system, which is a pair of stars formed by a white dwarf that attracts the outer layers of its companion star.

The binary system, which was called Gaia14aae, could also be an important laboratory for studying the supernova explosions used to estimate cosmic distances and thus to measure the expansion of the Universe. The details of this research will be published in the journal Monthly Notices of the Royal Astronomical Society and are available at this link.
Gaia14aae is located about 730 light-years away from us in the constellation Draco. It was discovered by the European Space Agency’s Gaia satellite in August 2014, when it increased its brightness suddenly becoming five times brighter over the course of a single day.
Astronomers led by Heather Campbell of Cambridge University analyzed data from Gaia and have determined that the sudden explosion was due to the fact that the white dwarf, a celestial body so dense that a teaspoon of the material that composes it weighs as much as an elephant, is devouring its great companion.
Additional observations by the Center for Backyard Astrophysics, a collaboration of amateurs and professionals, have shown that Gaia14aae is an eclipsing binary very rare, in which, from our vantage point, one star passes in front of another completely obscuring it. The two stars orbiting each other very quickly, so that a total eclipse occurs roughly every 50 minutes.
“It’s rare to see binary systems so well aligned,” said Heather Campbell of the Institute of Astronomy in Cambridge, who led the campaign of observations following the discovery for Gaia14aae. “Thanks to this feature, we can obtain very precise estimates of certain physical parameters of the system, and thus better understand how they are made and how to evolve these celestial bodies. It’s an interesting system; there is much to learn from it. ”
Using spectroscopic data collected by William Herschel Telescope in the Canary Islands, Campbell and his colleagues found that Gaia14aae contains large amounts of helium, but no trace of hydrogen, which is very unusual considering that hydrogen is the most common element in Universe. The lack of hydrogen has allowed to classify Gaia14aae as an extremely rare type of system Canum Venaticorum AM (AM CVN), which in turn is part of the class of Cataclysmic Variables, systems in which both stars have lost all their hydrogen. This is the first system type AM CVn for which it is observed one of the two stars totally eclipse the other.
“It’s very interesting that the first discovery of a system with these features come to the scientific community through the report of a group of amateur astronomers,” said Campbell. “This highlights the vital contribution that amateur astronomers provide scientific research.”
The systems of the type AM CVn are composed of a white dwarf, a star small, dense and hot that is literally devouring its companion largest. The gravitational effects of the white dwarf are so strong that it forces the companion star to swell like a balloon and move inexorably toward her.
The companion star has a volume of about 125 times that of the Sun, and therefore dominates the white dwarf, which has a similar size to the Earth (roughly like the comparison between a balloon and a ball). However, the companion star is slight: it contains only 1% of the mass of the white dwarf.
AM CVn binary systems are of great interest to astronomers, because they may provide the key to unlocking one of the greatest mysteries of modern astrophysics, i.e. what causes explosions of Type Ia supernova. This type of supernova is important in astrophysics because it produces a peak brightness of which we know the absolute value, and this makes it an important tool for measuring cosmic distances, and therefore the expansion of the Universe.
We do not know if the two stars will collide causing the explosion of a supernova, or if the white dwarf will have time to devour its entire companion before this explosive event will happen.
“This is an exceptional system: a rare binary system in which the orbits of the stars complete an orbit faster than the minute hand of a clock, and most are oriented to eclipse each other,” he said Tom Marsh from the University of Warwick. “We will be able to measure their sizes and masses with accuracy better than any system of its kind. This is very promising and creates very high expectations on the forthcoming findings of the Gaia satellite. ”
“It is an incredible record for Gaia, and we want to be the first of many,” said Simon Hodgkin Institute of Astronomy in Cambridge, who is leading the search for other sources variables, or transient data in Gaia. “Gaia has already found hundreds of transients in its first months of operation, and we know that there are still many to be discovered.”

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