Daisuke Nakauchi, Yudai Suwa, Takanori Sakamoto, Kazumi Kashiyama, Takashi Nakamura
Recent numerical simulations suggest that Population III (Pop III) stars are born with masses not larger than $\sim 100M_\odot$ but typically $\sim 40M_{\odot}$. We investigate whether such a low mass Pop III star can raise a Gamma Ray Burst (GRB) by considering the propagation of a jet, which is launched from the black hole, in the stellar envelope. It is generally believed that a super giant star is not an appropriate progenitor of a GRB, since the large envelope prevents the successful jet breakout. Especially for Pop III stars, the mass loss is not expected and the large hydrogen envelope is kept due to the low opacity envelope. We find, however, that those Pop III stars who end as blue super giants are compact enough for jets to break out the stellar envelopes successfully. We evaluate observational characters of Pop III GRBs and predict that Pop III GRBs have the duration of $\sim 10^5$ sec in the observer frame and the peak luminosity of $\sim 5 \times 10^{50}{\rm erg/sec}$. Moreover, assuming that the $E_p-L_p$ correlation (or the $E_p-E_{\gamma, \rm iso}$ correlation) holds for Pop III GRBs, we find that the spectrum peak energy falls $\sim$ a few keV (or $\sim 100$ keV) in the observer frame. We discuss the detectability of Pop III GRBs by future satellite missions such as EXIST and Lobster. If the $E_p-E_{\gamma, \rm iso}$ correlation holds for Pop III GRBs, we find that EXIST is more appropriate for GRB detections and that EXIST can detect Pop III GRBs at $z \lesssim 9$. We observe such Pop III GRBs at $z \sim 9$ as long duration X-ray rich GRBs by EXIST. On the other hand, if the $E_p-L_p$ correlation holds, we find that Lobster is more appropriate for detecting GRBs and that Lobster can detect very high z Pop III GRBs up to $z \sim 19$. We observe Pop III GRBs as long duration X-ray flashes by Lobster.
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http://arxiv.org/abs/1207.2835
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