BD-07 436

BD-07 436, also known as WASP-77 since 2012, is a binary star system about 344 light-years away. The star's components appears to have a different age, with the secondary older than 9 billion years, while the primary's age is 5 billion years. The BD-07 436 system's concentration of heavy elements is similar to the Sun. Its stars display moderate chromospheric activity, including x-ray flares.

The primary is a G-type main-sequence star, BD-07 436A (WASP-77A). The star is rotating rapidly, being spun up by the tides raised by the giant planet WASP-77Ab on its close orbit. The secondary is a K-type main-sequence star BD-07 436B orbiting at a distance of 461$$ AU.

Planetary system
In 2012 a transiting hot Jupiter planet b was detected on a very tight, circular orbit. The planet may have an extended gaseous envelope and is losing mass. Its equilibrium temperature is 1715$$ K, the nightside temperature measured in 2019 is 1786$$ K, and dayside planetary temperature measured in 2020 is 1842$$ K.

Water vapour was detected on the planetary dayside of WASP-77Ab, indicating C/O ratio similar to solar or even lower.