LONG-DURATION X-RAY FLASH AND X-RAY-RICH GAMMA-RAY BURSTS FROM LOW-MASS POPULATION III STARS

Recent numerical simulations suggest that Population III (Pop III) stars were born with masses not larger than ~100M sub([middot in circle]) and typically ~40M sub([middot in circle]). By self-consistently considering the jet generation and propagation in the envelope of these low-mass Pop III stars, we find that a Pop III blue supergiant star has the possibility of giving rise to a gamma-ray burst (GRB) even though it keeps a massive hydrogen envelope. We evaluate observational characteristics of Pop III GRBs and predict that Pop III GRBs have a duration of ~10 super(5) s in the observer frame and a peak luminosity of ~5 x 10 super(50) erg s super(-1). Assuming that the E sub(p)-L sub(p) (or E sub(p)-E sub( gamma ,iso)) correlation holds for Pop III GRBs, we find that the spectrum peak energy falls at approximately a few keV (or ~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 sub(p)-E sub( gamma ,iso)) correlation holds, we have the possibility to detect Pop III GRBs at z ~ 9 as long-duration X-ray-rich GRBs by EXIST. Conversely, if the E sub(p)-L sub(p) correlation holds, we have the possibility to detect Pop III GRBs up to z ~ 19 as long-duration X-ray flashes by Lobster.