VFTS102 has a projected rotational velocity ( > 500 km s ^ { -1 } ) and would appear to be the fastest rotating O-type star .
We show that its high rotational velocity could be understood within the framework of the binary merger .
In the binary merger channel , the progenitor binary of VFTS102 would evolve into contact while two components are still on the main sequence , and then merge into a rapidly rotating single star .
Employing Eggleton ’ s stellar evolution code , we performed binary stellar evolution calculations and mapped out the initial parameters of the progenitor of VFTS102 in the orbital period-mass ratio ( P - q ) plane .
We found that the progenitor binary of VFTS102 with initial mass ratio q _ { 0 } \la 0.7 should have an initial orbital period shorter than 3.76 - 4.25 days , while above this mass ratio it should have an initial orbital period shorter than 1.44 - 1.55 days .
The progenitor of VFTS102 would evolve into contact during the rapid mass transfer phase or during the subsequent slow mass transfer phase , and might ultimately merge into a rapidly rotating massive star .
In addition , we performed Monte Carlo simulations to investigate the binary merger channel .
We estimated the fraction of binaries that would merge into single stars and the fraction of single stars that might be produced from the binary merger channel .
It is found that about 8.7 % of binaries would evolve into contact and merge into rapidly rotating single stars , and about 17.1 % of single stars might be produced from the binary merger channel and should have similar properties to VFTS102 .
This suggests that the binary merger channel might be one of the main channels for the formation of rapidly rotating massive stars like VFTS102 .