Page "Blue straggler" Paragraph 6

The other explanation relies on mass transfer between two stars born in a binary star system.

The more massive of the two stars in the system will evolve first and as it expands, will overflow its Roche lobe.

Mass will quickly transfer from the initially more massive companion on to the less massive and like the collision hypothesis, would explain why there would be main sequence stars more massive than other stars in the cluster which have already evolved off of the main sequence.

Observations of blue stragglers have found that some are lacking in carbon and oxygen in their photospheres, which is evidence of having dredged up from the interior of a companion.