On the detection of very high redshift Gamma Ray Bursts with Swift
arXiv:0706.0657 · doi:10.1111/j.1745-3933.2007.00345.x
Abstract
We compute the probability to detect long Gamma Ray Bursts (GRBs) at z>5 with Swift, assuming that GRBs form preferentially in low-metallicity environments. The model fits well both the observed BATSE and Swift GRB differential peak flux distribution and is consistent with the number of z>2.5 detections in the 2-year Swift data. We find that the probability to observe a burst at z>5 becomes larger than 10% for photon fluxes P<1 ph s^{-1} cm^{-2}, consistent with the number of confirmed detections. The corresponding fraction of z>5 bursts in the Swift catalog is ~10%-30% depending on the adopted metallicity threshold for GRB formation. We propose to use the computed probability as a tool to identify high redshift GRBs. By jointly considering promptly-available information provided by Swift and model results, we can select reliable z>5 candidates in a few hours from the BAT detection. We test the procedure against last year Swift data: only three bursts match all our requirements, two being confirmed at z>5. Other three possible candidates are picked up by slightly relaxing the adopted criteria. No low-z interloper is found among the six candidates.
5 pages, 2 figures, MNRAS in press
References in corpus (7)
- The redshift distribution of SWIFT Gamma-Ray Bursts: evidence for evolution
- On the nature of nearby GRB/SN host galaxies
- Very different X-ray to optical column density ratios in gamma-ray burst afterglows: ionisation in GRB environments
- The Gamma Ray Burst Luminosity Function in the Light of the Swift 2-year Data
- The redshift distribution of gamma-ray bursts revisited
- The potential of INTEGRAL for the detection of high redshift GRBs
- Near real-time selection of high redshift GRBs with Swift