Binary star systems frequently appear as variable stars. When we cant see the private stars because they are either too close together or too far away, we can see the gradual dimming and brightening of a single point of light as the stars orbit each other. Often if the stars are especially close when they pass each other they can brighten in uncommon ways. One example of this is called a heart beat star.
They are called heart beat stars since if you outline their brightness in time, the pattern, or light curve, appears like a heartbeat seen on an electrocardiogram. Its the beeping pattern you see in movies and tv to show a character is still alive. Due to the fact that the two stars have highly eccentric orbits, heartbeat stars have such a pattern. Triggering them to brighten when they pass close to each other the tidal forces distort the stars into egg shapes. So you get a brief spike in brightness like a heart beat. We have a number of examples of heart beat stars, but a recently found one is uncommon even for a heartbeat star. Its peak brightness is 200 times greater than normal heartbeat stars, and its light curve has a rather unusual shape.
The light curve of MACHO 80.7443.1718. Credit: MacLeod & & Loeb
Called MACHO 80.7443.1718, the main star has a mass of 35 Suns, while the secondary star is simply 16 solar masses. They orbit each other once every 33 days, and at their closest method they are better than Mercury is to the Sun. The strong tidal forces during close approach help describe why they lighten up so considerably.
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Binary star systems often appear as variable stars. When we cant see the specific stars because they are either too close together or too far away, we can see the gradual dimming and lightening up of a single point of light as the stars orbit each other. Heartbeat stars have such a pattern because the 2 stars have highly eccentric orbits. We have several examples of heart beat stars, however a just recently found one is uncommon even for a heart beat star. The primary star rotates on its axis with a period of 4 days, so we see the waves pass along the star every couple of days.
Rather than having a simple spike of brightness, the stars dim a bit more slowly, and there is an oscillating decay to their light curve. To describe this, the team ran computer designs of the stars during close method, imitating not just the tidal forces between them, but likewise their fluid dynamics.
The first is that during the closest part of their orbit, some of the atmospheric product from the big star is captured by the smaller one. Lots of close binaries can exchange matter, however what is uncommon in this case is that the exchange activates oscillations in the main star. The primary star turns on its axis with a period of 4 days, so we see the waves pass along the star every few days.
MACHO 80.7443.1718 is a terrific example of simply how complicated binary star interactions can be. The heartbeat of this binary system does more than affect its brightness, it stirs the pot a bit, which could change the way the stars develop over time.
Referral: MacLeod, Morgan & & Loeb, Abraham. “Breaking waves on the surface of the heart beat star MACHO 80.7443.1718.” Nature Astronomy (2023 ).
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