(ORDO NEWS) — Scientists have discovered and studied a record system of a pulsar and a stellar remnant. The extreme proximity of the pulsar and the companion causes a powerful heating of the latter, accompanied by strong variable optical radiation.
The evolution of close binary star systems is replete with dramatic events. If the life path of a single star is almost uniquely determined by its mass, then in binary systems – depending on the mass of each component and the distance between them – many scenarios are possible. The most common of them is as follows.
As it becomes a red giant, the more massive star expands dozens of times and fills the Roche lobe , the region outside of which the companion’s tidal forces outweigh its own gravity.
In this case, the substance flows from the giant to the companion, which is why the first prematurely turns into a white dwarf, and the second is gaining mass. This stage is now in the Algol system , and in the past it may have been in the Sirius system.
The first act is relatively calm, but towards the end, the drama begins to gain momentum more and more rapidly. Having gained weight, the second star accelerates its evolution, and soon also turns into a red giant.
Here it is already time for the prematurely deceased first companion to feast: the white dwarf pulls the giant’s shell onto itself and begins to gain mass itself.
Accretion on compact objects is accompanied by much more violent phenomena than on ordinary Main Sequence stars.
From time to time, the matter pulled from the companion, shrinking and heating up on the surface of the white dwarf, explodes in nova outbursts, and if the mass of the white dwarf reaches the Chandrasekhar limit , then it itself explodes, becoming a type Ia supernova.
The smaller the distance between the components, the more intense the processes of mass exchange and the catastrophic phenomena caused by it.
In particularly close systems, the second companion can “retaliate”, especially if it is a neutron star. By shrinking its orbit through tidal friction, it could end up inside a red giant, turning it into an exotic object.
Sometimes a red giant has time to shed its shell before the neutron star, into which the first companion turned, plunged into its very core.
For some time, the resulting super-close system of the pulsar and the remnant of the second star becomes stable, but then, due to the emission of gravitational waves, the orbit becomes even tighter.
The pulsar begins to devour what is left of the less massive star with its tidal forces, and destroy the remnant with hard radiation. No wonder the prototype of such systems, PSR B1957 + 20 , astronomers called the “Black Widow”. The circulation period in it is only nine hours – and this is not the limit.
Typically, Black Widow-type systems are discovered by the characteristic X-ray and gamma radiation emitted by a pulsar.
Scientists from the Massachusetts Institute of Technology, led by Kevin Burge (Kevin Burdge), began to study the optical radiation of already known systems, as well as the search for new objects of this type, and discovered the most extreme system of a pulsar and a companion it eats known to date.
The orbital period in the newly discovered ZTF J1406+1222 system is only 62 minutes – a fast-paced waltz compared to a leisurely nine-hour promenade. This is faster than the theoretical limit for systems of a neutron star and a hydrogen remnant, and therefore the companion is either helium or heavier elements.
Once the companion ZTF J1406+1222 was itself a star, but now only a dense core remains of it, which revolves around the pulsar at about the same distance as the Moon from the Earth, and itself only three times the diameter of our planet.
Accretion onto neutron stars releases several times more energy than thermonuclear fusion, and all this energy is radiated from a region several hundred to thousands of kilometers in size.
The strongest hard radiation from the accretion disk and the pulsar itself falls on the companion, heating its “day” side to 10,100 degrees Celsius – almost twice as hot as the solar surface.
Typically, white dwarfs or their remnants are themselves heated to several thousand degrees, and their surface is comparable in brightness to the Sun. But even the light of our luminary cannot be compared with the heat of a nearby accretion disk.
Circling in orbit around the pulsar, the remnant turns to the Earth either by the “day” or “night” side, which causes fluctuations in its brightness in visible light by 13 times – these fluctuations were recorded by astronomers. Imagine: one side of our Sun was illuminated by something so bright that it itself began to show phases, like the Moon.
According to scientists, over time, the companion will be completely destroyed by the hard radiation and tidal forces of the pulsar. And this is where his bright life will end: in the absence of recharge, vampire pulsars in just some tens of millions of years slow down their frantic rotation and become the most ordinary neutron stars.
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