As we recall, are called pulsars permanent sources of cosmic radiation that comes to Earth in the form of periodic bursts (ie pulses). The family of pulsars, there are those who send us gamma-rays, as well as optical, X-ray and radio emission. The latter type of pulsar known better - as a rule, they are almost always of a binary system where a neutron star is adjacent to normal.
In fact, precisely because of such an interesting neighborhood and then there is the X-ray emission - more precisely, it provokes the bad behavior of the neutron star. The fact is that this cosmic retsidivistka constantly drags over substance, stolen from his neighbor. Basically a stellar gas - well, what else can you get hold of a star? So, when a neutron star accumulates a large amount of this gas, it forms an accretion disk around it, which gradually breaks down in areas that are close to the star (since the plasma into which turns this heated to a high temperature gas, can not go across the lines of magnetic field of light).
Well, if you can not cross, the plasma from the crumbling edge of the disc is nothing to do but to fall along the lines of force. In doing so, it reaches the surface of the neutron star in the poles. Contact with them so well that heats the plasma, which it provokes the launch of the surface of a thermonuclear reaction, which gives the X-rays. It is this radiation is just capture devices terrestrial astrophysicists.
But pulsars - is quite a different thing. First, mostly single neutron stars that no one do not steal. Secondly, they never surface fusion reaction - they generate radio signals quite different. It is believed that the rotation of the surface of a neutron star is constantly pulled out of elementary particles, which are in a strong magnetic field give rise to a secondary plasma. It begins to rotate together with a magnetic field whose lines of force near the poles remain unclosed.
Thus, the plasma formed near these same magnetic poles removed from the pulsar along the magnetic field lines, generating an radiosignaly.Kak see, X-ray and radio-emitting pulsars - it#39;s completely different objects. However, it is not strange, the first can be converted into the latter. Traditionally, it takes a long time: to stop emit X-rays, such a pair need to finish dragging the matter with a normal star to the neutron, and it takes millions of years. The opposite case, ie, the transformation in the X-ray pulsar, until recently, scientists were not known.
Recently, however, a team of astronomers led by Alessandro Papitto of the Catalan Institute for Space Studies (Spain) has found that neutron stars can transform from radio pulsars in X-ray pulsars in an extremely short time. Moreover, apparently, is possible, and the reverse transition. At this thought the researchers induced a study of neutron star IGR J18245-2452, which is located in a cluster M28 in the constellation Sagittarius at a distance of 18 million light-years from the Sun.
The history of this star is quite unusual - it was opened in 2005, and described as a radio pulsar. A little later, a different group of astronomers who are not familiar with the work of the pioneers, has described it as an X-ray pulsar. Interestingly, then, checking the data on the location of the object, scientists from both groups came to the conclusion that it is a single object. But that#39;s nothing - raising the archived information on the observations of several telescopes, astronomers from the group Papitto found that this star at all change the nature of their radiation several times a year!
Since it was found that often after a month of X-ray IGR J18245-2452 switched to the radio emission. And then a few more days, and the star begins to again generate X-rays. But how can this be? All this is particularly intriguing, as pulses are not coming from the X-ray pulsars, and X-rays should be stopped long before they can begin the radio emission - commented the lead author of the study prfessor Alessandro Papitto.
In order to deal with this issue, the researchers constructed a model of the behavior of this cosmic werewolf, which proposed the following mechanism for the change of radiation. It turned out that in the situation when the flow of plasma from the accretion disk collapsing suddenly stops, the star for a while can start to generate radio pulses - because the plasma from the surface evaporates constantly. Thus the X-ray pulsar at the time of the radio becomes. Well, when the fall of the plasma from the disk to restart the pole, the star will again become emit X-rays.
Well, for whatever reason, stop flow of material from the disk onto the star? Scientists suggest that this is due to neutron absorption cycles luminary new portion of the plasma, which is the star steals from his neighbor. While, when it comes to a new portion of stolen, the substance starts to fall from the disc onto the poles. But when feeding from the outside is not, the process stops and starts generating pulsar radio pulses.
It turns out that in fact the X-ray pulsars, and do not share the abyss to go through which takes millions of years. These objects can be transformed into each other in a shorter period of time. Apparently, the ability to emit X-rays and radio signals are at all relevant pulsars - it#39;s just different stages of their life cycle, alternating ...
