Protostellar Feedback and Final Mass of the Second-Generation Primordial
  Stars
  The first stars in the universe ionized the ambient primordial gas through
various feedback processes. "Second-generation" primordial stars potentially
form from this disturbed gas after its recombination. In this Letter, we study
the late formation stage of such second-generation stars, where a large amount
of gas accretes onto the protostar and the final stellar mass is determined
when the accretion terminates. We directly compute the complex interplay
between the accretion flow and stellar ultraviolet (UV) radiation, performing
radiation-hydrodynamic simulations coupled with stellar evolution calculations.
Because of more efficient H2 and HD cooling in the pre-stellar stage, the
accretion rates onto the star are ten times lower than in the case of the
formation of the first stars. The lower accretion rates and envelope density
result in the occurrence of an expanding bipolar HII region at a lower
protostellar mass M_* \simeq 10Msun, which blows out the circumstellar
material, thereby quenching the mass supply from the envelope to the accretion
disk. At the same time the disk loses mass due to photoevaporation by the
growing star. In our fiducial case the stellar UV feedback terminates mass
accretion onto the star at M_* \simeq 17Msun. Although the derived masses of
the second-generation primordial stars are systematically lower than those of
the first generation, the difference is within a factor of only a few. Our
results suggest a new scenario, whereby the majority of the primordial stars
are born as massive stars with tens of solar masses, regardless of their
generations.
