Can Planets Influence the Horizontal Branch Morphology?

As stars which have planetary systems evolve along the red giant branch andexpand, they interact with the close planets. The planets deposit angularmomentum and energy into the red giant stars' envelopes, both of which arelikely to enhance mass loss on the red giant branch. The enhanced mass losscauses the star to become bluer as it turns to the horizontal branch. I proposethat the presence of planetary systems, through this mechanism, can explainsome anomalies in horizontal branch morphologies. In particular, planetarysystems may be related to the ``second parameter'', which determines thedistribution of horizontal branch stars on the Hertzsprung-Russel diagram. Theproposed scenario predicts that surviving massive planets or brown dwarfs orbitmany of the extreme blue horizontal branch stars, at orbital periods of tensdays.Comment: 21 pages, preprint, uses aasms4.st