Delayed soft X-ray emission lines in the afterglow of GRB 030227

Strong delayed X-ray line emission is detected in the afterglow of gamma-ray burst GRB 030227, appearing near the end of the XMM-Newton observation, nearly 20 hr after the burst. The observed flux in the lines, not simply the equivalent width, sharply increases from an undetectable level (<1.7 x 10(-14) ergs cm(-2) s(-1), 3 sigma) to 4.1(-1.0)(+0.9) x 10(-14) ergs cm(-2) s(-1) in the final 9.7 ks. The line emission alone has nearly twice as many detected photons as any previous detection of X-ray lines. The lines correspond well to hydrogen- and/or helium-like emission from Mg, Si, S, Ar, and Ca at a redshift z = 1.39(-0.06)(+0.03). There is no evidence for Fe, Co, or Ni - the ultimate iron abundance must be less than a tenth that of the lighter metals. If the supernova and GRB events are nearly simultaneous, there must be continuing sporadic power output after the GRB of a luminosity greater than or similar to5 x 10(46) ergs s(-1), exceeding all but the most powerful quasars.