The planet around the horizontal-branch star HIP 13044

The evolution of the orbit of the planet detected around the horizontal-branch star HIP 13044 is considered. The initial semi-major axis of the planet’s orbit is estimated. A formula for the final result of the common-envelope stage in a close binary systemis used to estimate the mass of the envelope ejected by the red giant. The relatively small mass of this envelope (～0.1M _⊙) facilitated the survival of the planet after the partial dispersal of the envelope material and the transformation of the star into a horizontal-branch star.