How massive can a star be at birth? [duplicate]

We have discovered some incredibly massive stars. R136a1, the most massive known star is estimated to have 265 times mass as our Sun. Yet it has been burning for at least a million years, and must have shed a considerable mass as stellar wind. In its infancy, R136a1 must have been much more massive.

Which got me thinking about the question: What is the theoretical limit of mass that a newborn star can have?

• @Aaron: The question you linked seems to be rather vague. What do you mean by "size" when it comes to a star? Mass? Radius? :) Sep 15 '14 at 22:46
• @Krumia The accepted answer for that question interprets the question as mass. Sep 15 '14 at 23:52
• @HDE226868: And according to that answer, maximum limit is 2 $M_{Sun}$? :D (Not saying this is not a dupe, but that question should have another answer). Sep 16 '14 at 2:43
• "The article Stars Have a Size Limit by Michael Schirber, it's about 150 Solar Masses. However, there's the Pistol Star, which is speculated to be 200 SM." Sep 16 '14 at 6:11

I found a text that suggests a Population III star can have a mass between 200 and 10^5$M_{Sun}$. There you can read:
"...This would apply for VMOs larger than $M_c$ $\approx$ 200 $M_{Sun}$. Stars larger than 150$M_{Sun}$ are termed supermassive objects (SMOs)...".
It seems supermassive stars like R136a1 (with masses in excess 150$M_{Sun}$, the accepted upper limit for a non-pop III star) can be formed by the collision of massive stars.
So, It is not difficult to imagine, say, two 150$M_{Sun}$ monsters colliding and forming a 300$M_{Sun}$ object.
• So "Stars larger than $10^5M_{Sun}$ are termed supermassive objects (SMOs), and would collapse directly to black holes due to relativistic instabilities even before nuclear burning, at least if they were metal-free.". You should add that to the answer, I suppose :) Sep 15 '14 at 23:03