Variable stars frequently have binary star systems. When the stars are too close together or too far apart for us to discern the individual stars, we can still observe the steady brightening and dimming of a single point of light as the stars orbit one another. The stars can occasionally shine in peculiar ways when they pass each other if they are extremely close together. The heartbeat star is one illustration of this.
They are known as “heartbeat stars” because, when their brightness is plotted over time, the light-curve pattern resembles a heartbeat as seen on an ECG. It’s the beeping sound you hear when a character is still alive in movies and on television. Due of the two stars’ extraordinarily eccentric orbits, heartbeat stars exhibit this pattern. The stars are bent into egg forms by the tidal forces as they move in close proximity to one another, which makes them brighter. So you experience a brief increase in brightness that mimics a heartbeat. Heartbeat stars are common; nonetheless, a recently discovered one is exceptional even for a heartbeat star. Its light curve has a somewhat peculiar shape, and its peak brightness is 200 times greater than that of normal heartbeat stars.
The primary star, designated MACHO 80.7443.1718, has a mass of 35 Suns, while the secondary star has a mass of only 16 Suns. Each time they orbit one another, which takes 33 days, they come closer to the Sun than Mercury does. They brighten noticeably on close approach, which may be related to the powerful tidal forces.
The light curve does, however, have a peculiar feature. The stars dim slightly more slowly, and their light curve oscillates as opposed to just peaking in brightness. The scientists used computer simulations of the stars during close approach to explain this, calculating both their fluid dynamics and the tidal forces that act between them. They discovered a few intriguing things.
The first is that some of the large star’s atmosphere is taken by the smaller one when they are quite close to one another. It is common for near binaries to exchange materials, however in this instance it is remarkable since the oscillations in the primary star are caused by the exchange. Waves appear on the parent star’s surface as the companion passes by. Then, along the surface, these waves cascade. We observe the waves passing along the star every few days since the parent star rotates on its axis with a period of four days. This explains why the light curve’s decline is shaky.
One excellent illustration of how intricate binary star interactions may be is MACHO 80.7443.1718. This binary system’s heartbeat alters more than just its brightness; it also stirs things up a bit, which might have an impact on how the stars develop over time.
