# How to determine the mass of a runaway star?

I would like to know how do astronomers estimate the mass of a star that has been ejected from its galaxy. What kind of accuracy can be achieved?

• What is a "rogue star"? – Rob Jeffries Mar 18 '16 at 7:49
• @RobJeffries: I believe any star that is "kicked out" by their own galaxy gets demoted to rogue star. – user6760 Mar 18 '16 at 9:26
• In that case the mass is estimated in the same way as any other star. You put it on an HR diagram and match it up with a stellar model. If the distance is unknown then you have to use the "spectroscopists" HR diagram by estimating the surface gravity to place it in the evolutionary lifecycle and then using the temperature to estimate the mass. – Rob Jeffries Mar 18 '16 at 10:46
• Closely related, and possibly a duplicate, astronomy.stackexchange.com/questions/11342/… – Rob Jeffries Mar 18 '16 at 10:47
• I could provide a more detailed answer if you tell me exactly what the context is and what observational material might be available. – Rob Jeffries Mar 18 '16 at 10:48

The details are found in Evans et al. (2010). It is probably fair to say that the estimate of $90\ M_{\odot}$, is uncertain by a few tens of solar masses.