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Cleaning pursue


Thanks to detailed observations to X-rays obtained with the telescope NASA space, it has been discovered that the pulsar within the system known under the name B1259 has “cleaned” the disc of the companion star by pushing out a portion of material, which even seems to accelerate as it moves away. The results were published in The Astrophysical Journal.
It seems that a pulsar has pierced the gas disk of its companion star, throwing a portion of the disk outward at a speed of about 4.5 million kilometers per hour. The X-ray telescope Chandra NASA is tracking this “cosmic lump,” which seems to pick up speed as it moves away. The binary system called PSR B1259-63 / LS 2883, said B1259 for short, consists of a star with a mass 30 times that of the Sun and a pulsar or a neutron star, a celestial body extremely dense remnant of the central regions of a star even more massive a result of its explosion as supernova.

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Credit: NASA/CXC/PSU

The pulsar emits regular pulses as it rotates on itself 20 times per second, and moves along a highly elliptical orbit around its companion. The combination of the very fast rotation and strong magnetic field generates a strong wind of high energy particles that move away from the pulsar with speeds approaching the speed of light. The companion star, in turn, rotates on itself with a speed close to that break, the speed limit beyond which the centrifugal force wins against the force of gravity leading to the disintegration of the star, and produces around him a disc gas. Every 41 months, the pulsar passes to periastron, the point of closest approach to the partner, and at that moment crossing the disk of gas.
“These two objects have a very peculiar arrangement and were given the opportunity to witness something special,” said George Pavlov of Penn State University, lead author of the paper describing these results. “It appears that during one of the last of the pulsar transits across the disk portion of the media has been pushed out and released into space.”
Although this “lump” of the material has quite large, about a hundred times our Solar System, it is also quite rare. The material has in fact a mass equivalent to all the water present in the earth’s oceans.
“After the expulsion of this portion of the material, the pulsar wind seems to have accelerated, almost as if it were attached to a rocket,” said co-author Oleg Kargaltsev of George Washington University (GWU). B1259 is about 7,500 light years from Earth, and astronomers have observed three times with Chandra between December 2011 and February 2014. These observations show that the material ejected from the disk moves away from B1259 at an average speed of about 7% of the speed of light. The data also indicate that the material has been accelerated between the second and the third observation.
“This shows just how powerful the wind emitted by a pulsar,” explained co-author Jeremy Hare, also of the GWU. “The wind of the pulsar PSR B1259-63 is so strong that, over time, could get to break up completely the disk of the companion star.” The X-ray emission observed by Chandra is probably due to a shock wave generated by the impact of pulsar wind disk. The pressure generated by this interaction could also be responsible of the acceleration suffered subsequently by the material itself. The Chandra telescope will continue to monitor B1259 and its “lump” in motion with Hubble observations by the end of this year and for 2016.

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