Detectability of GRB Iron Lines by Swift, Chandra and XMM
Abstract
The rapid acquisition of positions by the upcoming Swift satellite will allow the monitoring for X-ray lines in GRB afterglows at much earlier epochs than waspreviously feasible. We calculate the possible significance levels of iron line detections as a function of source redshift and observing time after the trigger, for the Swift XRT, Chandra ACIS and XMM Epic detectors. For standard burst luminosities and decay rates and equivalent widths of 1 keV as previously reported, depending on the source-frame epoch at which the lines appear, Swift may be able to detect lines up to z~7 with a significance of better than 3 sigma. Equivalent widths of 0.5 keV should be detectable with better than 4.5 sigma at z up to ~8 by Chandra, and at z up to ~11 by XMM. For higher initial luminosities, as seen in some GRBs and as might be the case in population III bursts, similar significance levels are obtained out to substantially higher redshifts. For standard burst parameters, Chandra can distinguish between broad and narrow lines to better than 3 sigma up to z ~ 6,while Swift can do so up to z~0.5. For the higher luminosities, Swift is able to distinguish at the 5 sigma level between a broad and a narrow line up to z ~3, and between a 6.7 kev vs. a 6.4 keV line center up to z ~5.Keywords
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